GMain: allow NULL context to g_source_attach

[platform/upstream/glib.git] / glib / gmain.c

/* GLIB - Library of useful routines for C programming
 * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
 *
 * gmain.c: Main loop abstraction, timeouts, and idle functions
 * Copyright 1998 Owen Taylor
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/*
 * Modified by the GLib Team and others 1997-2000.  See the AUTHORS
 * file for a list of people on the GLib Team.  See the ChangeLog
 * files for a list of changes.  These files are distributed with
 * GLib at ftp://ftp.gtk.org/pub/gtk/.
 */

/*
 * MT safe
 */

#include "config.h"
#include "glibconfig.h"

/* Uncomment the next line (and the corresponding line in gpoll.c) to
 * enable debugging printouts if the environment variable
 * G_MAIN_POLL_DEBUG is set to some value.
 */
/* #define G_MAIN_POLL_DEBUG */

#ifdef _WIN32
/* Always enable debugging printout on Windows, as it is more often
 * needed there...
 */
#define G_MAIN_POLL_DEBUG
#endif

#ifdef G_OS_UNIX
#include "glib-unix.h"
#include <pthread.h>
#ifdef HAVE_EVENTFD
#include <sys/eventfd.h>
#endif
#endif

#include <signal.h>
#include <sys/types.h>
#include <time.h>
#include <stdlib.h>
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif /* HAVE_SYS_TIME_H */
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif /* HAVE_UNISTD_H */
#include <errno.h>
#include <string.h>

#ifdef G_OS_WIN32
#define STRICT
#include <windows.h>
#endif /* G_OS_WIN32 */

#ifdef G_OS_BEOS
#include <sys/socket.h>
#include <sys/wait.h>
#endif /* G_OS_BEOS */

#include "gmain.h"

#include "garray.h"
#include "giochannel.h"
#include "ghash.h"
#include "ghook.h"
#include "gqueue.h"
#include "gstrfuncs.h"
#include "gtestutils.h"

#ifdef G_OS_WIN32
#include "gwin32.h"
#endif

#ifdef  G_MAIN_POLL_DEBUG
#include "gtimer.h"
#endif

#include "gwakeup.h"
#include "gmain-internal.h"
#include "glib-private.h"

/**
 * SECTION:main
 * @title: The Main Event Loop
 * @short_description: manages all available sources of events
 *
 * The main event loop manages all the available sources of events for
 * GLib and GTK+ applications. These events can come from any number of
 * different types of sources such as file descriptors (plain files,
 * pipes or sockets) and timeouts. New types of event sources can also
 * be added using g_source_attach().
 *
 * To allow multiple independent sets of sources to be handled in
 * different threads, each source is associated with a #GMainContext.
 * A GMainContext can only be running in a single thread, but
 * sources can be added to it and removed from it from other threads.
 *
 * Each event source is assigned a priority. The default priority,
 * #G_PRIORITY_DEFAULT, is 0. Values less than 0 denote higher priorities.
 * Values greater than 0 denote lower priorities. Events from high priority
 * sources are always processed before events from lower priority sources.
 *
 * Idle functions can also be added, and assigned a priority. These will
 * be run whenever no events with a higher priority are ready to be processed.
 *
 * The #GMainLoop data type represents a main event loop. A GMainLoop is
 * created with g_main_loop_new(). After adding the initial event sources,
 * g_main_loop_run() is called. This continuously checks for new events from
 * each of the event sources and dispatches them. Finally, the processing of
 * an event from one of the sources leads to a call to g_main_loop_quit() to
 * exit the main loop, and g_main_loop_run() returns.
 *
 * It is possible to create new instances of #GMainLoop recursively.
 * This is often used in GTK+ applications when showing modal dialog
 * boxes. Note that event sources are associated with a particular
 * #GMainContext, and will be checked and dispatched for all main
 * loops associated with that GMainContext.
 *
 * GTK+ contains wrappers of some of these functions, e.g. gtk_main(),
 * gtk_main_quit() and gtk_events_pending().
 *
 * <refsect2><title>Creating new source types</title>
 * <para>One of the unusual features of the #GMainLoop functionality
 * is that new types of event source can be created and used in
 * addition to the builtin type of event source. A new event source
 * type is used for handling GDK events. A new source type is created
 * by <firstterm>deriving</firstterm> from the #GSource structure.
 * The derived type of source is represented by a structure that has
 * the #GSource structure as a first element, and other elements specific
 * to the new source type. To create an instance of the new source type,
 * call g_source_new() passing in the size of the derived structure and
 * a table of functions. These #GSourceFuncs determine the behavior of
 * the new source type.</para>
 * <para>New source types basically interact with the main context
 * in two ways. Their prepare function in #GSourceFuncs can set a timeout
 * to determine the maximum amount of time that the main loop will sleep
 * before checking the source again. In addition, or as well, the source
 * can add file descriptors to the set that the main context checks using
 * g_source_add_poll().</para>
 * </refsect2>
 * <refsect2><title>Customizing the main loop iteration</title>
 * <para>Single iterations of a #GMainContext can be run with
 * g_main_context_iteration(). In some cases, more detailed control
 * of exactly how the details of the main loop work is desired, for
 * instance, when integrating the #GMainLoop with an external main loop.
 * In such cases, you can call the component functions of
 * g_main_context_iteration() directly. These functions are
 * g_main_context_prepare(), g_main_context_query(),
 * g_main_context_check() and g_main_context_dispatch().</para>
 * <para>The operation of these functions can best be seen in terms
 * of a state diagram, as shown in <xref linkend="mainloop-states"/>.</para>
 * <figure id="mainloop-states"><title>States of a Main Context</title>
 * <graphic fileref="mainloop-states.gif" format="GIF"></graphic>
 * </figure>
 * </refsect2>
 *
 * On Unix, the GLib mainloop is incompatible with fork().  Any program
 * using the mainloop must either exec() or exit() from the child
 * without returning to the mainloop.
 */

/* Types */

typedef struct _GTimeoutSource GTimeoutSource;
typedef struct _GChildWatchSource GChildWatchSource;
typedef struct _GUnixSignalWatchSource GUnixSignalWatchSource;
typedef struct _GPollRec GPollRec;
typedef struct _GSourceCallback GSourceCallback;

typedef enum
{
  G_SOURCE_READY = 1 << G_HOOK_FLAG_USER_SHIFT,
  G_SOURCE_CAN_RECURSE = 1 << (G_HOOK_FLAG_USER_SHIFT + 1)
} GSourceFlags;

typedef struct _GMainWaiter GMainWaiter;

struct _GMainWaiter
{
  GCond *cond;
  GMutex *mutex;
};

typedef struct _GMainDispatch GMainDispatch;

struct _GMainDispatch
{
  gint depth;
  GSList *dispatching_sources; /* stack of current sources */
};

#ifdef G_MAIN_POLL_DEBUG
gboolean _g_main_poll_debug = FALSE;
#endif

struct _GMainContext
{
  /* The following lock is used for both the list of sources
   * and the list of poll records
   */
  GMutex mutex;
  GCond cond;
  GThread *owner;
  guint owner_count;
  GSList *waiters;

  gint ref_count;

  GPtrArray *pending_dispatches;
  gint timeout;                 /* Timeout for current iteration */

  guint next_id;
  GSource *source_list;
  gint in_check_or_prepare;

  GPollRec *poll_records, *poll_records_tail;
  guint n_poll_records;
  GPollFD *cached_poll_array;
  guint cached_poll_array_size;

  GWakeup *wakeup;

  GPollFD wake_up_rec;

/* Flag indicating whether the set of fd's changed during a poll */
  gboolean poll_changed;

  GPollFunc poll_func;

  gint64   time;
  gboolean time_is_fresh;
};

struct _GSourceCallback
{
  guint ref_count;
  GSourceFunc func;
  gpointer    data;
  GDestroyNotify notify;
};

struct _GMainLoop
{
  GMainContext *context;
  gboolean is_running;
  gint ref_count;
};

struct _GTimeoutSource
{
  GSource     source;
  gint64      expiration;
  guint       interval;
  gboolean    seconds;
};

struct _GChildWatchSource
{
  GSource     source;
  GPid        pid;
  gint        child_status;
#ifdef G_OS_WIN32
  GPollFD     poll;
#else /* G_OS_WIN32 */
  gboolean    child_exited;
#endif /* G_OS_WIN32 */
};

struct _GUnixSignalWatchSource
{
  GSource     source;
  int         signum;
  gboolean    pending;
};

struct _GPollRec
{
  GPollFD *fd;
  GPollRec *prev;
  GPollRec *next;
  gint priority;
};

struct _GSourcePrivate
{
  GSList *child_sources;
  GSource *parent_source;
};

#define LOCK_CONTEXT(context) g_mutex_lock (&context->mutex)
#define UNLOCK_CONTEXT(context) g_mutex_unlock (&context->mutex)
#define G_THREAD_SELF g_thread_self ()

#define SOURCE_DESTROYED(source) (((source)->flags & G_HOOK_FLAG_ACTIVE) == 0)
#define SOURCE_BLOCKED(source) (((source)->flags & G_HOOK_FLAG_IN_CALL) != 0 && \
                                ((source)->flags & G_SOURCE_CAN_RECURSE) == 0)

#define SOURCE_UNREF(source, context)                       \
   G_STMT_START {                                           \
    if ((source)->ref_count > 1)                            \
      (source)->ref_count--;                                \
    else                                                    \
      g_source_unref_internal ((source), (context), TRUE);  \
   } G_STMT_END


/* Forward declarations */

static void g_source_unref_internal             (GSource      *source,
                                                 GMainContext *context,
                                                 gboolean      have_lock);
static void g_source_destroy_internal           (GSource      *source,
                                                 GMainContext *context,
                                                 gboolean      have_lock);
static void g_source_set_priority_unlocked      (GSource      *source,
                                                 GMainContext *context,
                                                 gint          priority);
static void g_main_context_poll                 (GMainContext *context,
                                                 gint          timeout,
                                                 gint          priority,
                                                 GPollFD      *fds,
                                                 gint          n_fds);
static void g_main_context_add_poll_unlocked    (GMainContext *context,
                                                 gint          priority,
                                                 GPollFD      *fd);
static void g_main_context_remove_poll_unlocked (GMainContext *context,
                                                 GPollFD      *fd);

static gboolean g_timeout_prepare  (GSource     *source,
                                    gint        *timeout);
static gboolean g_timeout_check    (GSource     *source);
static gboolean g_timeout_dispatch (GSource     *source,
                                    GSourceFunc  callback,
                                    gpointer     user_data);
static gboolean g_child_watch_prepare  (GSource     *source,
                                        gint        *timeout);
static gboolean g_child_watch_check    (GSource     *source);
static gboolean g_child_watch_dispatch (GSource     *source,
                                        GSourceFunc  callback,
                                        gpointer     user_data);
static void     g_child_watch_finalize (GSource     *source);
#ifdef G_OS_UNIX
static void g_unix_signal_handler (int signum);
static gboolean g_unix_signal_watch_prepare  (GSource     *source,
                                              gint        *timeout);
static gboolean g_unix_signal_watch_check    (GSource     *source);
static gboolean g_unix_signal_watch_dispatch (GSource     *source,
                                              GSourceFunc  callback,
                                              gpointer     user_data);
static void     g_unix_signal_watch_finalize  (GSource     *source);
#endif
static gboolean g_idle_prepare     (GSource     *source,
                                    gint        *timeout);
static gboolean g_idle_check       (GSource     *source);
static gboolean g_idle_dispatch    (GSource     *source,
                                    GSourceFunc  callback,
                                    gpointer     user_data);

static GMainContext *glib_worker_context;

G_LOCK_DEFINE_STATIC (main_loop);
static GMainContext *default_main_context;

#ifndef G_OS_WIN32


/* UNIX signals work by marking one of these variables then waking the
 * worker context to check on them and dispatch accordingly.
 */
static volatile gchar unix_signal_pending[NSIG];
static volatile gboolean any_unix_signal_pending;

/* Guards all the data below */
G_LOCK_DEFINE_STATIC (unix_signal_lock);
static GSList *unix_signal_watches;
static GSList *unix_child_watches;

static GSourceFuncs g_unix_signal_funcs =
{
  g_unix_signal_watch_prepare,
  g_unix_signal_watch_check,
  g_unix_signal_watch_dispatch,
  g_unix_signal_watch_finalize
};
#endif /* !G_OS_WIN32 */
G_LOCK_DEFINE_STATIC (main_context_list);
static GSList *main_context_list = NULL;

GSourceFuncs g_timeout_funcs =
{
  g_timeout_prepare,
  g_timeout_check,
  g_timeout_dispatch,
  NULL
};

GSourceFuncs g_child_watch_funcs =
{
  g_child_watch_prepare,
  g_child_watch_check,
  g_child_watch_dispatch,
  g_child_watch_finalize
};

GSourceFuncs g_idle_funcs =
{
  g_idle_prepare,
  g_idle_check,
  g_idle_dispatch,
  NULL
};

/**
 * g_main_context_ref:
 * @context: a #GMainContext
 * 
 * Increases the reference count on a #GMainContext object by one.
 *
 * Returns: the @context that was passed in (since 2.6)
 **/
GMainContext *
g_main_context_ref (GMainContext *context)
{
  g_return_val_if_fail (context != NULL, NULL);
  g_return_val_if_fail (g_atomic_int_get (&context->ref_count) > 0, NULL); 

  g_atomic_int_inc (&context->ref_count);

  return context;
}

static inline void
poll_rec_list_free (GMainContext *context,
                    GPollRec     *list)
{
  g_slice_free_chain (GPollRec, list, next);
}

/**
 * g_main_context_unref:
 * @context: a #GMainContext
 * 
 * Decreases the reference count on a #GMainContext object by one. If
 * the result is zero, free the context and free all associated memory.
 **/
void
g_main_context_unref (GMainContext *context)
{
  GSource *source;
  g_return_if_fail (context != NULL);
  g_return_if_fail (g_atomic_int_get (&context->ref_count) > 0); 

  if (!g_atomic_int_dec_and_test (&context->ref_count))
    return;

  G_LOCK (main_context_list);
  main_context_list = g_slist_remove (main_context_list, context);
  G_UNLOCK (main_context_list);

  source = context->source_list;
  while (source)
    {
      GSource *next = source->next;
      g_source_destroy_internal (source, context, FALSE);
      source = next;
    }

  g_mutex_clear (&context->mutex);

  g_ptr_array_free (context->pending_dispatches, TRUE);
  g_free (context->cached_poll_array);

  poll_rec_list_free (context, context->poll_records);

  g_wakeup_free (context->wakeup);
  g_cond_clear (&context->cond);

  g_free (context);
}

/**
 * g_main_context_new:
 * 
 * Creates a new #GMainContext structure.
 * 
 * Return value: the new #GMainContext
 **/
GMainContext *
g_main_context_new (void)
{
  static gsize initialised;
  GMainContext *context;

  if (g_once_init_enter (&initialised))
    {
#ifdef G_MAIN_POLL_DEBUG
      if (getenv ("G_MAIN_POLL_DEBUG") != NULL)
        _g_main_poll_debug = TRUE;
#endif

      g_once_init_leave (&initialised, TRUE);
    }

  context = g_new0 (GMainContext, 1);

  g_mutex_init (&context->mutex);
  g_cond_init (&context->cond);

  context->owner = NULL;
  context->waiters = NULL;

  context->ref_count = 1;

  context->next_id = 1;
  
  context->source_list = NULL;
  
  context->poll_func = g_poll;
  
  context->cached_poll_array = NULL;
  context->cached_poll_array_size = 0;
  
  context->pending_dispatches = g_ptr_array_new ();
  
  context->time_is_fresh = FALSE;
  
  context->wakeup = g_wakeup_new ();
  g_wakeup_get_pollfd (context->wakeup, &context->wake_up_rec);
  g_main_context_add_poll_unlocked (context, 0, &context->wake_up_rec);

  G_LOCK (main_context_list);
  main_context_list = g_slist_append (main_context_list, context);

#ifdef G_MAIN_POLL_DEBUG
  if (_g_main_poll_debug)
    g_print ("created context=%p\n", context);
#endif

  G_UNLOCK (main_context_list);

  return context;
}

/**
 * g_main_context_default:
 * 
 * Returns the global default main context. This is the main context
 * used for main loop functions when a main loop is not explicitly
 * specified, and corresponds to the "main" main loop. See also
 * g_main_context_get_thread_default().
 * 
 * Return value: (transfer none): the global default main context.
 **/
GMainContext *
g_main_context_default (void)
{
  /* Slow, but safe */
  
  G_LOCK (main_loop);

  if (!default_main_context)
    {
      default_main_context = g_main_context_new ();
#ifdef G_MAIN_POLL_DEBUG
      if (_g_main_poll_debug)
        g_print ("default context=%p\n", default_main_context);
#endif
    }

  G_UNLOCK (main_loop);

  return default_main_context;
}

static void
free_context_stack (gpointer data)
{
  GQueue *stack = data;
  GMainContext *context;

  while (!g_queue_is_empty (stack))
    {
      context = g_queue_pop_head (stack);
      g_main_context_release (context);
      if (context)
        g_main_context_unref (context);
    }
  g_queue_free (stack);
}

static GPrivate thread_context_stack = G_PRIVATE_INIT (free_context_stack);

/**
 * g_main_context_push_thread_default:
 * @context: a #GMainContext, or %NULL for the global default context
 *
 * Acquires @context and sets it as the thread-default context for the
 * current thread. This will cause certain asynchronous operations
 * (such as most <link linkend="gio">gio</link>-based I/O) which are
 * started in this thread to run under @context and deliver their
 * results to its main loop, rather than running under the global
 * default context in the main thread. Note that calling this function
 * changes the context returned by
 * g_main_context_get_thread_default(), <emphasis>not</emphasis> the
 * one returned by g_main_context_default(), so it does not affect the
 * context used by functions like g_idle_add().
 *
 * Normally you would call this function shortly after creating a new
 * thread, passing it a #GMainContext which will be run by a
 * #GMainLoop in that thread, to set a new default context for all
 * async operations in that thread. (In this case, you don't need to
 * ever call g_main_context_pop_thread_default().) In some cases
 * however, you may want to schedule a single operation in a
 * non-default context, or temporarily use a non-default context in
 * the main thread. In that case, you can wrap the call to the
 * asynchronous operation inside a
 * g_main_context_push_thread_default() /
 * g_main_context_pop_thread_default() pair, but it is up to you to
 * ensure that no other asynchronous operations accidentally get
 * started while the non-default context is active.
 *
 * Beware that libraries that predate this function may not correctly
 * handle being used from a thread with a thread-default context. Eg,
 * see g_file_supports_thread_contexts().
 *
 * Since: 2.22
 **/
void
g_main_context_push_thread_default (GMainContext *context)
{
  GQueue *stack;
  gboolean acquired_context;

  acquired_context = g_main_context_acquire (context);
  g_return_if_fail (acquired_context);

  if (context == g_main_context_default ())
    context = NULL;
  else if (context)
    g_main_context_ref (context);

  stack = g_private_get (&thread_context_stack);
  if (!stack)
    {
      stack = g_queue_new ();
      g_private_set (&thread_context_stack, stack);
    }

  g_queue_push_head (stack, context);
}

/**
 * g_main_context_pop_thread_default:
 * @context: a #GMainContext object, or %NULL
 *
 * Pops @context off the thread-default context stack (verifying that
 * it was on the top of the stack).
 *
 * Since: 2.22
 **/
void
g_main_context_pop_thread_default (GMainContext *context)
{
  GQueue *stack;

  if (context == g_main_context_default ())
    context = NULL;

  stack = g_private_get (&thread_context_stack);

  g_return_if_fail (stack != NULL);
  g_return_if_fail (g_queue_peek_head (stack) == context);

  g_queue_pop_head (stack);

  g_main_context_release (context);
  if (context)
    g_main_context_unref (context);
}

/**
 * g_main_context_get_thread_default:
 *
 * Gets the thread-default #GMainContext for this thread. Asynchronous
 * operations that want to be able to be run in contexts other than
 * the default one should call this method or
 * g_main_context_ref_thread_default() to get a #GMainContext to add
 * their #GSource<!-- -->s to. (Note that even in single-threaded
 * programs applications may sometimes want to temporarily push a
 * non-default context, so it is not safe to assume that this will
 * always return %NULL if you are running in the default thread.)
 *
 * If you need to hold a reference on the context, use
 * g_main_context_ref_thread_default() instead.
 *
 * Returns: (transfer none): the thread-default #GMainContext, or
 * %NULL if the thread-default context is the global default context.
 *
 * Since: 2.22
 **/
GMainContext *
g_main_context_get_thread_default (void)
{
  GQueue *stack;

  stack = g_private_get (&thread_context_stack);
  if (stack)
    return g_queue_peek_head (stack);
  else
    return NULL;
}

/**
 * g_main_context_ref_thread_default:
 *
 * Gets the thread-default #GMainContext for this thread, as with
 * g_main_context_get_thread_default(), but also adds a reference to
 * it with g_main_context_ref(). In addition, unlike
 * g_main_context_get_thread_default(), if the thread-default context
 * is the global default context, this will return that #GMainContext
 * (with a ref added to it) rather than returning %NULL.
 *
 * Returns: (transfer full): the thread-default #GMainContext. Unref
 *     with g_main_context_unref() when you are done with it.
 *
 * Since: 2.32
 */
GMainContext *
g_main_context_ref_thread_default (void)
{
  GMainContext *context;

  context = g_main_context_get_thread_default ();
  if (!context)
    context = g_main_context_default ();
  return g_main_context_ref (context);
}

/* Hooks for adding to the main loop */

/**
 * g_source_new:
 * @source_funcs: structure containing functions that implement
 *                the sources behavior.
 * @struct_size: size of the #GSource structure to create.
 * 
 * Creates a new #GSource structure. The size is specified to
 * allow creating structures derived from #GSource that contain
 * additional data. The size passed in must be at least
 * <literal>sizeof (GSource)</literal>.
 * 
 * The source will not initially be associated with any #GMainContext
 * and must be added to one with g_source_attach() before it will be
 * executed.
 * 
 * Return value: the newly-created #GSource.
 **/
GSource *
g_source_new (GSourceFuncs *source_funcs,
              guint         struct_size)
{
  GSource *source;

  g_return_val_if_fail (source_funcs != NULL, NULL);
  g_return_val_if_fail (struct_size >= sizeof (GSource), NULL);
  
  source = (GSource*) g_malloc0 (struct_size);

  source->source_funcs = source_funcs;
  source->ref_count = 1;
  
  source->priority = G_PRIORITY_DEFAULT;

  source->flags = G_HOOK_FLAG_ACTIVE;

  /* NULL/0 initialization for all other fields */
  
  return source;
}

/* Holds context's lock
 */
static void
g_source_list_add (GSource      *source,
                   GMainContext *context)
{
  GSource *tmp_source, *last_source;
  
  if (source->priv && source->priv->parent_source)
    {
      /* Put the source immediately before its parent */
      tmp_source = source->priv->parent_source;
      last_source = source->priv->parent_source->prev;
    }
  else
    {
      last_source = NULL;
      tmp_source = context->source_list;
      while (tmp_source && tmp_source->priority <= source->priority)
        {
          last_source = tmp_source;
          tmp_source = tmp_source->next;
        }
    }

  source->next = tmp_source;
  if (tmp_source)
    tmp_source->prev = source;
  
  source->prev = last_source;
  if (last_source)
    last_source->next = source;
  else
    context->source_list = source;
}

/* Holds context's lock
 */
static void
g_source_list_remove (GSource      *source,
                      GMainContext *context)
{
  if (source->prev)
    source->prev->next = source->next;
  else
    context->source_list = source->next;

  if (source->next)
    source->next->prev = source->prev;

  source->prev = NULL;
  source->next = NULL;
}

static guint
g_source_attach_unlocked (GSource      *source,
                          GMainContext *context)
{
  guint result = 0;
  GSList *tmp_list;

  source->context = context;
  result = source->source_id = context->next_id++;

  source->ref_count++;
  g_source_list_add (source, context);

  tmp_list = source->poll_fds;
  while (tmp_list)
    {
      g_main_context_add_poll_unlocked (context, source->priority, tmp_list->data);
      tmp_list = tmp_list->next;
    }

  if (source->priv)
    {
      tmp_list = source->priv->child_sources;
      while (tmp_list)
        {
          g_source_attach_unlocked (tmp_list->data, context);
          tmp_list = tmp_list->next;
        }
    }

  return result;
}

/**
 * g_source_attach:
 * @source: a #GSource
 * @context: (allow-none): a #GMainContext (if %NULL, the default context will be used)
 * 
 * Adds a #GSource to a @context so that it will be executed within
 * that context. Remove it by calling g_source_destroy().
 *
 * Return value: the ID (greater than 0) for the source within the 
 *   #GMainContext. 
 **/
guint
g_source_attach (GSource      *source,
                 GMainContext *context)
{
  guint result = 0;

  g_return_val_if_fail (source->context == NULL, 0);
  g_return_val_if_fail (!SOURCE_DESTROYED (source), 0);
  
  if (!context)
    context = g_main_context_default ();

  LOCK_CONTEXT (context);

  result = g_source_attach_unlocked (source, context);

  /* If another thread has acquired the context, wake it up since it
   * might be in poll() right now.
   */
  if (context->owner && context->owner != G_THREAD_SELF)
    g_wakeup_signal (context->wakeup);

  UNLOCK_CONTEXT (context);

  return result;
}

static void
g_source_destroy_internal (GSource      *source,
                           GMainContext *context,
                           gboolean      have_lock)
{
  if (!have_lock)
    LOCK_CONTEXT (context);
  
  if (!SOURCE_DESTROYED (source))
    {
      GSList *tmp_list;
      gpointer old_cb_data;
      GSourceCallbackFuncs *old_cb_funcs;
      
      source->flags &= ~G_HOOK_FLAG_ACTIVE;

      old_cb_data = source->callback_data;
      old_cb_funcs = source->callback_funcs;

      source->callback_data = NULL;
      source->callback_funcs = NULL;

      if (old_cb_funcs)
        {
          UNLOCK_CONTEXT (context);
          old_cb_funcs->unref (old_cb_data);
          LOCK_CONTEXT (context);
        }

      if (!SOURCE_BLOCKED (source))
        {
          tmp_list = source->poll_fds;
          while (tmp_list)
            {
              g_main_context_remove_poll_unlocked (context, tmp_list->data);
              tmp_list = tmp_list->next;
            }
        }

      if (source->priv && source->priv->child_sources)
        {
          /* This is safe because even if a child_source finalizer or
           * closure notify tried to modify source->priv->child_sources
           * from outside the lock, it would fail since
           * SOURCE_DESTROYED(source) is now TRUE.
           */
          tmp_list = source->priv->child_sources;
          while (tmp_list)
            {
              g_source_destroy_internal (tmp_list->data, context, TRUE);
              g_source_unref_internal (tmp_list->data, context, TRUE);
              tmp_list = tmp_list->next;
            }
          g_slist_free (source->priv->child_sources);
          source->priv->child_sources = NULL;
        }
          
      g_source_unref_internal (source, context, TRUE);
    }

  if (!have_lock)
    UNLOCK_CONTEXT (context);
}

/**
 * g_source_destroy:
 * @source: a #GSource
 * 
 * Removes a source from its #GMainContext, if any, and mark it as
 * destroyed.  The source cannot be subsequently added to another
 * context.
 **/
void
g_source_destroy (GSource *source)
{
  GMainContext *context;
  
  g_return_if_fail (source != NULL);
  
  context = source->context;
  
  if (context)
    g_source_destroy_internal (source, context, FALSE);
  else
    source->flags &= ~G_HOOK_FLAG_ACTIVE;
}

/**
 * g_source_get_id:
 * @source: a #GSource
 * 
 * Returns the numeric ID for a particular source. The ID of a source
 * is a positive integer which is unique within a particular main loop 
 * context. The reverse
 * mapping from ID to source is done by g_main_context_find_source_by_id().
 *
 * Return value: the ID (greater than 0) for the source
 **/
guint
g_source_get_id (GSource *source)
{
  guint result;
  
  g_return_val_if_fail (source != NULL, 0);
  g_return_val_if_fail (source->context != NULL, 0);

  LOCK_CONTEXT (source->context);
  result = source->source_id;
  UNLOCK_CONTEXT (source->context);
  
  return result;
}

/**
 * g_source_get_context:
 * @source: a #GSource
 * 
 * Gets the #GMainContext with which the source is associated.
 * Calling this function on a destroyed source is an error.
 * 
 * Return value: (transfer none): the #GMainContext with which the
 *               source is associated, or %NULL if the context has not
 *               yet been added to a source.
 **/
GMainContext *
g_source_get_context (GSource *source)
{
  g_return_val_if_fail (!SOURCE_DESTROYED (source), NULL);

  return source->context;
}

/**
 * g_source_add_poll:
 * @source:a #GSource 
 * @fd: a #GPollFD structure holding information about a file
 *      descriptor to watch.
 * 
 * Adds a file descriptor to the set of file descriptors polled for
 * this source. This is usually combined with g_source_new() to add an
 * event source. The event source's check function will typically test
 * the @revents field in the #GPollFD struct and return %TRUE if events need
 * to be processed.
 **/
void
g_source_add_poll (GSource *source,
                   GPollFD *fd)
{
  GMainContext *context;
  
  g_return_if_fail (source != NULL);
  g_return_if_fail (fd != NULL);
  g_return_if_fail (!SOURCE_DESTROYED (source));
  
  context = source->context;

  if (context)
    LOCK_CONTEXT (context);
  
  source->poll_fds = g_slist_prepend (source->poll_fds, fd);

  if (context)
    {
      if (!SOURCE_BLOCKED (source))
        g_main_context_add_poll_unlocked (context, source->priority, fd);
      UNLOCK_CONTEXT (context);
    }
}

/**
 * g_source_remove_poll:
 * @source:a #GSource 
 * @fd: a #GPollFD structure previously passed to g_source_add_poll().
 * 
 * Removes a file descriptor from the set of file descriptors polled for
 * this source. 
 **/
void
g_source_remove_poll (GSource *source,
                      GPollFD *fd)
{
  GMainContext *context;
  
  g_return_if_fail (source != NULL);
  g_return_if_fail (fd != NULL);
  g_return_if_fail (!SOURCE_DESTROYED (source));
  
  context = source->context;

  if (context)
    LOCK_CONTEXT (context);
  
  source->poll_fds = g_slist_remove (source->poll_fds, fd);

  if (context)
    {
      if (!SOURCE_BLOCKED (source))
        g_main_context_remove_poll_unlocked (context, fd);
      UNLOCK_CONTEXT (context);
    }
}

/**
 * g_source_add_child_source:
 * @source:a #GSource
 * @child_source: a second #GSource that @source should "poll"
 *
 * Adds @child_source to @source as a "polled" source; when @source is
 * added to a #GMainContext, @child_source will be automatically added
 * with the same priority, when @child_source is triggered, it will
 * cause @source to dispatch (in addition to calling its own
 * callback), and when @source is destroyed, it will destroy
 * @child_source as well. (@source will also still be dispatched if
 * its own prepare/check functions indicate that it is ready.)
 *
 * If you don't need @child_source to do anything on its own when it
 * triggers, you can call g_source_set_dummy_callback() on it to set a
 * callback that does nothing (except return %TRUE if appropriate).
 *
 * @source will hold a reference on @child_source while @child_source
 * is attached to it.
 *
 * Since: 2.28
 **/
void
g_source_add_child_source (GSource *source,
                           GSource *child_source)
{
  GMainContext *context;

  g_return_if_fail (source != NULL);
  g_return_if_fail (child_source != NULL);
  g_return_if_fail (!SOURCE_DESTROYED (source));
  g_return_if_fail (!SOURCE_DESTROYED (child_source));
  g_return_if_fail (child_source->context == NULL);
  g_return_if_fail (child_source->priv == NULL || child_source->priv->parent_source == NULL);

  context = source->context;

  if (context)
    LOCK_CONTEXT (context);

  if (!source->priv)
    source->priv = g_slice_new0 (GSourcePrivate);
  if (!child_source->priv)
    child_source->priv = g_slice_new0 (GSourcePrivate);

  source->priv->child_sources = g_slist_prepend (source->priv->child_sources,
                                                 g_source_ref (child_source));
  child_source->priv->parent_source = source;
  g_source_set_priority_unlocked (child_source, context, source->priority);

  if (context)
    {
      UNLOCK_CONTEXT (context);
      g_source_attach (child_source, context);
    }
}

/**
 * g_source_remove_child_source:
 * @source:a #GSource
 * @child_source: a #GSource previously passed to
 *     g_source_add_child_source().
 *
 * Detaches @child_source from @source and destroys it.
 *
 * Since: 2.28
 **/
void
g_source_remove_child_source (GSource *source,
                              GSource *child_source)
{
  GMainContext *context;

  g_return_if_fail (source != NULL);
  g_return_if_fail (child_source != NULL);
  g_return_if_fail (child_source->priv != NULL && child_source->priv->parent_source == source);
  g_return_if_fail (!SOURCE_DESTROYED (source));
  g_return_if_fail (!SOURCE_DESTROYED (child_source));

  context = source->context;

  if (context)
    LOCK_CONTEXT (context);

  source->priv->child_sources = g_slist_remove (source->priv->child_sources, child_source);
  g_source_destroy_internal (child_source, context, TRUE);
  g_source_unref_internal (child_source, context, TRUE);

  if (context)
    UNLOCK_CONTEXT (context);
}

/**
 * g_source_set_callback_indirect:
 * @source: the source
 * @callback_data: pointer to callback data "object"
 * @callback_funcs: functions for reference counting @callback_data
 *                  and getting the callback and data
 * 
 * Sets the callback function storing the data as a refcounted callback
 * "object". This is used internally. Note that calling 
 * g_source_set_callback_indirect() assumes
 * an initial reference count on @callback_data, and thus
 * @callback_funcs->unref will eventually be called once more
 * than @callback_funcs->ref.
 **/
void
g_source_set_callback_indirect (GSource              *source,
                                gpointer              callback_data,
                                GSourceCallbackFuncs *callback_funcs)
{
  GMainContext *context;
  gpointer old_cb_data;
  GSourceCallbackFuncs *old_cb_funcs;
  
  g_return_if_fail (source != NULL);
  g_return_if_fail (callback_funcs != NULL || callback_data == NULL);

  context = source->context;

  if (context)
    LOCK_CONTEXT (context);

  old_cb_data = source->callback_data;
  old_cb_funcs = source->callback_funcs;

  source->callback_data = callback_data;
  source->callback_funcs = callback_funcs;
  
  if (context)
    UNLOCK_CONTEXT (context);
  
  if (old_cb_funcs)
    old_cb_funcs->unref (old_cb_data);
}

static void
g_source_callback_ref (gpointer cb_data)
{
  GSourceCallback *callback = cb_data;

  callback->ref_count++;
}


static void
g_source_callback_unref (gpointer cb_data)
{
  GSourceCallback *callback = cb_data;

  callback->ref_count--;
  if (callback->ref_count == 0)
    {
      if (callback->notify)
        callback->notify (callback->data);
      g_free (callback);
    }
}

static void
g_source_callback_get (gpointer     cb_data,
                       GSource     *source, 
                       GSourceFunc *func,
                       gpointer    *data)
{
  GSourceCallback *callback = cb_data;

  *func = callback->func;
  *data = callback->data;
}

static GSourceCallbackFuncs g_source_callback_funcs = {
  g_source_callback_ref,
  g_source_callback_unref,
  g_source_callback_get,
};

/**
 * g_source_set_callback:
 * @source: the source
 * @func: a callback function
 * @data: the data to pass to callback function
 * @notify: a function to call when @data is no longer in use, or %NULL.
 * 
 * Sets the callback function for a source. The callback for a source is
 * called from the source's dispatch function.
 *
 * The exact type of @func depends on the type of source; ie. you
 * should not count on @func being called with @data as its first
 * parameter.
 * 
 * Typically, you won't use this function. Instead use functions specific
 * to the type of source you are using.
 **/
void
g_source_set_callback (GSource        *source,
                       GSourceFunc     func,
                       gpointer        data,
                       GDestroyNotify  notify)
{
  GSourceCallback *new_callback;

  g_return_if_fail (source != NULL);

  new_callback = g_new (GSourceCallback, 1);

  new_callback->ref_count = 1;
  new_callback->func = func;
  new_callback->data = data;
  new_callback->notify = notify;

  g_source_set_callback_indirect (source, new_callback, &g_source_callback_funcs);
}


/**
 * g_source_set_funcs:
 * @source: a #GSource
 * @funcs: the new #GSourceFuncs
 * 
 * Sets the source functions (can be used to override 
 * default implementations) of an unattached source.
 * 
 * Since: 2.12
 */
void
g_source_set_funcs (GSource     *source,
                   GSourceFuncs *funcs)
{
  g_return_if_fail (source != NULL);
  g_return_if_fail (source->context == NULL);
  g_return_if_fail (source->ref_count > 0);
  g_return_if_fail (funcs != NULL);

  source->source_funcs = funcs;
}

static void
g_source_set_priority_unlocked (GSource      *source,
                                GMainContext *context,
                                gint          priority)
{
  GSList *tmp_list;
  
  source->priority = priority;

  if (context)
    {
      /* Remove the source from the context's source and then
       * add it back so it is sorted in the correct place
       */
      g_source_list_remove (source, source->context);
      g_source_list_add (source, source->context);

      if (!SOURCE_BLOCKED (source))
        {
          tmp_list = source->poll_fds;
          while (tmp_list)
            {
              g_main_context_remove_poll_unlocked (context, tmp_list->data);
              g_main_context_add_poll_unlocked (context, priority, tmp_list->data);
              
              tmp_list = tmp_list->next;
            }
        }
    }

  if (source->priv && source->priv->child_sources)
    {
      tmp_list = source->priv->child_sources;
      while (tmp_list)
        {
          g_source_set_priority_unlocked (tmp_list->data, context, priority);
          tmp_list = tmp_list->next;
        }
    }
}

/**
 * g_source_set_priority:
 * @source: a #GSource
 * @priority: the new priority.
 *
 * Sets the priority of a source. While the main loop is being run, a
 * source will be dispatched if it is ready to be dispatched and no
 * sources at a higher (numerically smaller) priority are ready to be
 * dispatched.
 **/
void
g_source_set_priority (GSource  *source,
                       gint      priority)
{
  GMainContext *context;

  g_return_if_fail (source != NULL);

  context = source->context;

  if (context)
    LOCK_CONTEXT (context);
  g_source_set_priority_unlocked (source, context, priority);
  if (context)
    UNLOCK_CONTEXT (source->context);
}

/**
 * g_source_get_priority:
 * @source: a #GSource
 * 
 * Gets the priority of a source.
 * 
 * Return value: the priority of the source
 **/
gint
g_source_get_priority (GSource *source)
{
  g_return_val_if_fail (source != NULL, 0);

  return source->priority;
}

/**
 * g_source_set_can_recurse:
 * @source: a #GSource
 * @can_recurse: whether recursion is allowed for this source
 * 
 * Sets whether a source can be called recursively. If @can_recurse is
 * %TRUE, then while the source is being dispatched then this source
 * will be processed normally. Otherwise, all processing of this
 * source is blocked until the dispatch function returns.
 **/
void
g_source_set_can_recurse (GSource  *source,
                          gboolean  can_recurse)
{
  GMainContext *context;
  
  g_return_if_fail (source != NULL);

  context = source->context;

  if (context)
    LOCK_CONTEXT (context);
  
  if (can_recurse)
    source->flags |= G_SOURCE_CAN_RECURSE;
  else
    source->flags &= ~G_SOURCE_CAN_RECURSE;

  if (context)
    UNLOCK_CONTEXT (context);
}

/**
 * g_source_get_can_recurse:
 * @source: a #GSource
 * 
 * Checks whether a source is allowed to be called recursively.
 * see g_source_set_can_recurse().
 * 
 * Return value: whether recursion is allowed.
 **/
gboolean
g_source_get_can_recurse (GSource  *source)
{
  g_return_val_if_fail (source != NULL, FALSE);
  
  return (source->flags & G_SOURCE_CAN_RECURSE) != 0;
}


/**
 * g_source_set_name:
 * @source: a #GSource
 * @name: debug name for the source
 *
 * Sets a name for the source, used in debugging and profiling.
 * The name defaults to #NULL.
 *
 * The source name should describe in a human-readable way
 * what the source does. For example, "X11 event queue"
 * or "GTK+ repaint idle handler" or whatever it is.
 *
 * It is permitted to call this function multiple times, but is not
 * recommended due to the potential performance impact.  For example,
 * one could change the name in the "check" function of a #GSourceFuncs 
 * to include details like the event type in the source name.
 *
 * Since: 2.26
 **/
void
g_source_set_name (GSource    *source,
                   const char *name)
{
  g_return_if_fail (source != NULL);

  /* setting back to NULL is allowed, just because it's
   * weird if get_name can return NULL but you can't
   * set that.
   */

  g_free (source->name);
  source->name = g_strdup (name);
}

/**
 * g_source_get_name:
 * @source: a #GSource
 *
 * Gets a name for the source, used in debugging and profiling.
 * The name may be #NULL if it has never been set with
 * g_source_set_name().
 *
 * Return value: the name of the source
 * Since: 2.26
 **/
const char *
g_source_get_name (GSource *source)
{
  g_return_val_if_fail (source != NULL, NULL);

  return source->name;
}

/**
 * g_source_set_name_by_id:
 * @tag: a #GSource ID
 * @name: debug name for the source
 *
 * Sets the name of a source using its ID.
 *
 * This is a convenience utility to set source names from the return
 * value of g_idle_add(), g_timeout_add(), etc.
 *
 * Since: 2.26
 **/
void
g_source_set_name_by_id (guint           tag,
                         const char     *name)
{
  GSource *source;

  g_return_if_fail (tag > 0);

  source = g_main_context_find_source_by_id (NULL, tag);
  if (source == NULL)
    return;

  g_source_set_name (source, name);
}


/**
 * g_source_ref:
 * @source: a #GSource
 * 
 * Increases the reference count on a source by one.
 * 
 * Return value: @source
 **/
GSource *
g_source_ref (GSource *source)
{
  GMainContext *context;
  
  g_return_val_if_fail (source != NULL, NULL);

  context = source->context;

  if (context)
    LOCK_CONTEXT (context);

  source->ref_count++;

  if (context)
    UNLOCK_CONTEXT (context);

  return source;
}

/* g_source_unref() but possible to call within context lock
 */
static void
g_source_unref_internal (GSource      *source,
                         GMainContext *context,
                         gboolean      have_lock)
{
  gpointer old_cb_data = NULL;
  GSourceCallbackFuncs *old_cb_funcs = NULL;

  g_return_if_fail (source != NULL);
  
  if (!have_lock && context)
    LOCK_CONTEXT (context);

  source->ref_count--;
  if (source->ref_count == 0)
    {
      old_cb_data = source->callback_data;
      old_cb_funcs = source->callback_funcs;

      source->callback_data = NULL;
      source->callback_funcs = NULL;

      if (context)
        {
          if (!SOURCE_DESTROYED (source))
            g_warning (G_STRLOC ": ref_count == 0, but source was still attached to a context!");
          g_source_list_remove (source, context);
        }

      if (source->source_funcs->finalize)
        {
          if (context)
            UNLOCK_CONTEXT (context);
          source->source_funcs->finalize (source);
          if (context)
            LOCK_CONTEXT (context);
        }

      g_free (source->name);
      source->name = NULL;

      g_slist_free (source->poll_fds);
      source->poll_fds = NULL;

      if (source->priv)
        {
          g_slice_free (GSourcePrivate, source->priv);
          source->priv = NULL;
        }

      g_free (source);
    }
  
  if (!have_lock && context)
    UNLOCK_CONTEXT (context);

  if (old_cb_funcs)
    {
      if (have_lock)
        UNLOCK_CONTEXT (context);
      
      old_cb_funcs->unref (old_cb_data);

      if (have_lock)
        LOCK_CONTEXT (context);
    }
}

/**
 * g_source_unref:
 * @source: a #GSource
 * 
 * Decreases the reference count of a source by one. If the
 * resulting reference count is zero the source and associated
 * memory will be destroyed. 
 **/
void
g_source_unref (GSource *source)
{
  g_return_if_fail (source != NULL);

  g_source_unref_internal (source, source->context, FALSE);
}

/**
 * g_main_context_find_source_by_id:
 * @context: a #GMainContext (if %NULL, the default context will be used)
 * @source_id: the source ID, as returned by g_source_get_id(). 
 * 
 * Finds a #GSource given a pair of context and ID.
 * 
 * Return value: (transfer none): the #GSource if found, otherwise, %NULL
 **/
GSource *
g_main_context_find_source_by_id (GMainContext *context,
                                  guint         source_id)
{
  GSource *source;
  
  g_return_val_if_fail (source_id > 0, NULL);

  if (context == NULL)
    context = g_main_context_default ();
  
  LOCK_CONTEXT (context);
  
  source = context->source_list;
  while (source)
    {
      if (!SOURCE_DESTROYED (source) &&
          source->source_id == source_id)
        break;
      source = source->next;
    }

  UNLOCK_CONTEXT (context);

  return source;
}

/**
 * g_main_context_find_source_by_funcs_user_data:
 * @context: a #GMainContext (if %NULL, the default context will be used).
 * @funcs: the @source_funcs passed to g_source_new().
 * @user_data: the user data from the callback.
 * 
 * Finds a source with the given source functions and user data.  If
 * multiple sources exist with the same source function and user data,
 * the first one found will be returned.
 * 
 * Return value: (transfer none): the source, if one was found, otherwise %NULL
 **/
GSource *
g_main_context_find_source_by_funcs_user_data (GMainContext *context,
                                               GSourceFuncs *funcs,
                                               gpointer      user_data)
{
  GSource *source;
  
  g_return_val_if_fail (funcs != NULL, NULL);

  if (context == NULL)
    context = g_main_context_default ();
  
  LOCK_CONTEXT (context);

  source = context->source_list;
  while (source)
    {
      if (!SOURCE_DESTROYED (source) &&
          source->source_funcs == funcs &&
          source->callback_funcs)
        {
          GSourceFunc callback;
          gpointer callback_data;

          source->callback_funcs->get (source->callback_data, source, &callback, &callback_data);
          
          if (callback_data == user_data)
            break;
        }
      source = source->next;
    }

  UNLOCK_CONTEXT (context);

  return source;
}

/**
 * g_main_context_find_source_by_user_data:
 * @context: a #GMainContext
 * @user_data: the user_data for the callback.
 * 
 * Finds a source with the given user data for the callback.  If
 * multiple sources exist with the same user data, the first
 * one found will be returned.
 * 
 * Return value: (transfer none): the source, if one was found, otherwise %NULL
 **/
GSource *
g_main_context_find_source_by_user_data (GMainContext *context,
                                         gpointer      user_data)
{
  GSource *source;
  
  if (context == NULL)
    context = g_main_context_default ();
  
  LOCK_CONTEXT (context);

  source = context->source_list;
  while (source)
    {
      if (!SOURCE_DESTROYED (source) &&
          source->callback_funcs)
        {
          GSourceFunc callback;
          gpointer callback_data = NULL;

          source->callback_funcs->get (source->callback_data, source, &callback, &callback_data);

          if (callback_data == user_data)
            break;
        }
      source = source->next;
    }

  UNLOCK_CONTEXT (context);

  return source;
}

/**
 * g_source_remove:
 * @tag: the ID of the source to remove.
 * 
 * Removes the source with the given id from the default main context. 
 * The id of
 * a #GSource is given by g_source_get_id(), or will be returned by the
 * functions g_source_attach(), g_idle_add(), g_idle_add_full(),
 * g_timeout_add(), g_timeout_add_full(), g_child_watch_add(),
 * g_child_watch_add_full(), g_io_add_watch(), and g_io_add_watch_full().
 *
 * See also g_source_destroy(). You must use g_source_destroy() for sources
 * added to a non-default main context.
 *
 * Return value: %TRUE if the source was found and removed.
 **/
gboolean
g_source_remove (guint tag)
{
  GSource *source;
  
  g_return_val_if_fail (tag > 0, FALSE);

  source = g_main_context_find_source_by_id (NULL, tag);
  if (source)
    g_source_destroy (source);

  return source != NULL;
}

/**
 * g_source_remove_by_user_data:
 * @user_data: the user_data for the callback.
 * 
 * Removes a source from the default main loop context given the user
 * data for the callback. If multiple sources exist with the same user
 * data, only one will be destroyed.
 * 
 * Return value: %TRUE if a source was found and removed. 
 **/
gboolean
g_source_remove_by_user_data (gpointer user_data)
{
  GSource *source;
  
  source = g_main_context_find_source_by_user_data (NULL, user_data);
  if (source)
    {
      g_source_destroy (source);
      return TRUE;
    }
  else
    return FALSE;
}

/**
 * g_source_remove_by_funcs_user_data:
 * @funcs: The @source_funcs passed to g_source_new()
 * @user_data: the user data for the callback
 * 
 * Removes a source from the default main loop context given the
 * source functions and user data. If multiple sources exist with the
 * same source functions and user data, only one will be destroyed.
 * 
 * Return value: %TRUE if a source was found and removed. 
 **/
gboolean
g_source_remove_by_funcs_user_data (GSourceFuncs *funcs,
                                    gpointer      user_data)
{
  GSource *source;

  g_return_val_if_fail (funcs != NULL, FALSE);

  source = g_main_context_find_source_by_funcs_user_data (NULL, funcs, user_data);
  if (source)
    {
      g_source_destroy (source);
      return TRUE;
    }
  else
    return FALSE;
}

/**
 * g_get_current_time:
 * @result: #GTimeVal structure in which to store current time.
 *
 * Equivalent to the UNIX gettimeofday() function, but portable.
 *
 * You may find g_get_real_time() to be more convenient.
 **/
void
g_get_current_time (GTimeVal *result)
{
#ifndef G_OS_WIN32
  struct timeval r;

  g_return_if_fail (result != NULL);

  /*this is required on alpha, there the timeval structs are int's
    not longs and a cast only would fail horribly*/
  gettimeofday (&r, NULL);
  result->tv_sec = r.tv_sec;
  result->tv_usec = r.tv_usec;
#else
  FILETIME ft;
  guint64 time64;

  g_return_if_fail (result != NULL);

  GetSystemTimeAsFileTime (&ft);
  memmove (&time64, &ft, sizeof (FILETIME));

  /* Convert from 100s of nanoseconds since 1601-01-01
   * to Unix epoch. Yes, this is Y2038 unsafe.
   */
  time64 -= G_GINT64_CONSTANT (116444736000000000);
  time64 /= 10;

  result->tv_sec = time64 / 1000000;
  result->tv_usec = time64 % 1000000;
#endif
}

/**
 * g_get_real_time:
 *
 * Queries the system wall-clock time.
 *
 * This call is functionally equivalent to g_get_current_time() except
 * that the return value is often more convenient than dealing with a
 * #GTimeVal.
 *
 * You should only use this call if you are actually interested in the real
 * wall-clock time.  g_get_monotonic_time() is probably more useful for
 * measuring intervals.
 *
 * Returns: the number of microseconds since January 1, 1970 UTC.
 *
 * Since: 2.28
 **/
gint64
g_get_real_time (void)
{
  GTimeVal tv;

  g_get_current_time (&tv);

  return (((gint64) tv.tv_sec) * 1000000) + tv.tv_usec;
}

#ifdef G_OS_WIN32
static ULONGLONG (*g_GetTickCount64) (void) = NULL;
static guint32 g_win32_tick_epoch = 0;

G_GNUC_INTERNAL void
g_clock_win32_init (void)
{
  HMODULE kernel32;

  g_GetTickCount64 = NULL;
  kernel32 = GetModuleHandle ("KERNEL32.DLL");
  if (kernel32 != NULL)
    g_GetTickCount64 = (void *) GetProcAddress (kernel32, "GetTickCount64");
  g_win32_tick_epoch = ((guint32)GetTickCount()) >> 31;
}
#endif

/**
 * g_get_monotonic_time:
 *
 * Queries the system monotonic time, if available.
 *
 * On POSIX systems with clock_gettime() and %CLOCK_MONOTONIC this call
 * is a very shallow wrapper for that.  Otherwise, we make a best effort
 * that probably involves returning the wall clock time (with at least
 * microsecond accuracy, subject to the limitations of the OS kernel).
 *
 * It's important to note that POSIX %CLOCK_MONOTONIC does not count
 * time spent while the machine is suspended.
 *
 * On Windows, "limitations of the OS kernel" is a rather substantial
 * statement.  Depending on the configuration of the system, the wall
 * clock time is updated as infrequently as 64 times a second (which
 * is approximately every 16ms). Also, the on XP (not on Vista or later)
 * the monitonic clock is locally monotonic, but may differ in exact
 * value between processes due to timer wrap handling.
 *
 * Returns: the monotonic time, in microseconds
 *
 * Since: 2.28
 **/
gint64
g_get_monotonic_time (void)
{
#ifdef HAVE_CLOCK_GETTIME
  /* librt clock_gettime() is our first choice */
  struct timespec ts;

#ifdef CLOCK_MONOTONIC
  clock_gettime (CLOCK_MONOTONIC, &ts);
#else
  clock_gettime (CLOCK_REALTIME, &ts);
#endif

  /* In theory monotonic time can have any epoch.
   *
   * glib presently assumes the following:
   *
   *   1) The epoch comes some time after the birth of Jesus of Nazareth, but
   *      not more than 10000 years later.
   *
   *   2) The current time also falls sometime within this range.
   *
   * These two reasonable assumptions leave us with a maximum deviation from
   * the epoch of 10000 years, or 315569520000000000 seconds.
   *
   * If we restrict ourselves to this range then the number of microseconds
   * will always fit well inside the constraints of a int64 (by a factor of
   * about 29).
   *
   * If you actually hit the following assertion, probably you should file a
   * bug against your operating system for being excessively silly.
   **/
  g_assert (G_GINT64_CONSTANT (-315569520000000000) < ts.tv_sec &&
            ts.tv_sec < G_GINT64_CONSTANT (315569520000000000));

  return (((gint64) ts.tv_sec) * 1000000) + (ts.tv_nsec / 1000);

#elif defined (G_OS_WIN32)
  guint64 ticks;
  guint32 ticks32;

  /* There are four of sources for the monotonic on windows:
   *
   * Three are based on a (1 msec accuracy, but only read periodically) clock chip:
   * - GetTickCount (GTC)
   *    32bit msec counter, updated each ~15msec, wraps in ~50 days
   * - GetTickCount64 (GTC64)
   *    Same as GetTickCount, but extended to 64bit, so no wrap
   *    Only availible in Vista or later
   * - timeGetTime (TGT)
   *    similar to GetTickCount by default: 15msec, 50 day wrap.
   *    availible in winmm.dll (thus known as the multi media timers) 
   *    However apps can raise the system timer clock frequency using timeBeginPeriod()
   *    increasing the accuracy up to 1 msec, at a cost in general system performancs
   *    and battery use.
   *
   * One is based on high precision clocks:
   * - QueryPrecisionCounter (QPC)
   *    This has much higher accuracy, but is not guaranteed monotonic, and
   *    has lots of complications like clock jumps and different times on different
   *    cpus. It also has lower long term accuracy (i.e. it will drift compared to
   *    the low precision clocks.
   *
   * Additionally, the precision availible in the timer-based wakeup such as
   * MsgWaitForMultipleObjectsEx (which is what the mainloop is based on) is based
   * on the TGT resolution, so by default it is ~15msec, but can be increased by apps.
   *
   * The QPC timer has too many issues to be used as is. The only way it could be used
   * is to use it to interpolate the lower precision clocks. Firefox does something like
   * this:
   *   https://bugzilla.mozilla.org/show_bug.cgi?id=363258
   * 
   * However this seems quite complicated, so we're not doing this right now.
   *
   * The approach we take instead is to use the TGT timer, extenting it to 64bit
   * either by using the GTC64 value, or if that is not availible, a process local
   * time epoch that we increment when we detect a timer wrap (assumes that we read
   * the time at least once every 50 days).
   *
   * This means that:
   *  - We have a globally consistent monotonic clock on Vista and later
   *  - We have a locally monotonic clock on XP
   *  - Apps that need higher precision in timeouts and clock reads can call 
   *    timeBeginPeriod() to increase it as much as they want
   */

  if (g_GetTickCount64 != NULL)
    {
      guint32 ticks_as_32bit;

      ticks = g_GetTickCount64 ();
      ticks32 = timeGetTime();

      /* GTC64 and TGT are sampled at different times, however they 
       * have the same base and source (msecs since system boot). 
       * They can differ with as much as -16 to +16 msecs.
       * We can't just inject the low bits into the 64bit counter 
       * as one of the counters can have wrapped in 32bit space and
       * the other not. Instead we calulate the signed differece
       * in 32bit space and apply that difference to the 64bit counter.
       */
      ticks_as_32bit = (guint32)ticks;

      /* We could do some 2s complement hack, but we play it safe */
      if (ticks32 - ticks_as_32bit <= G_MAXINT32)
        ticks += ticks32 - ticks_as_32bit;
      else
        ticks -= ticks_as_32bit - ticks32;
    }
  else
    {
      guint32 epoch;

      epoch = g_atomic_int_get (&g_win32_tick_epoch);

      /* Must read ticks after the epoch, then we're guaranteed
         that the ticks value we read is higher or equal to any
         previous ones that lead to the writing of the epoch. */
      ticks32 = timeGetTime();

      /* We store the msb of the current time as the lsb
       * of the epoch. Comparing these bits lets us detect when
       * the 32bit counter has wrapped so we can increase the
       * epoch.
       * This will work as long as this function is called at
       * least once every ~24 days, which is half the wrap time
       * of a 32bit msec counter. I think this is pretty likely.
       *
       * Note that g_win32_tick_epoch is a process local state,
       * so the monotonic clock will not be the same between
       * processes.
       */
      if ((ticks32 >> 31) != (epoch & 1))
        {
          epoch++;
          g_atomic_int_set (&g_win32_tick_epoch, epoch);
        }


      ticks = (guint64)ticks32 | ((guint64)epoch) << 31;
    }

  return ticks * 1000;

#else /* !HAVE_CLOCK_GETTIME && ! G_OS_WIN32*/

  /* It may look like we are discarding accuracy on Windows (since its
   * current time is expressed in 100s of nanoseconds) but according to
   * many sources, the time is only updated 64 times per second, so
   * microsecond accuracy is more than enough.
   */
  GTimeVal tv;

  g_get_current_time (&tv);

  return (((gint64) tv.tv_sec) * 1000000) + tv.tv_usec;
#endif
}

static void
g_main_dispatch_free (gpointer dispatch)
{
  g_slice_free (GMainDispatch, dispatch);
}

/* Running the main loop */

static GMainDispatch *
get_dispatch (void)
{
  static GPrivate depth_private = G_PRIVATE_INIT (g_main_dispatch_free);
  GMainDispatch *dispatch;

  dispatch = g_private_get (&depth_private);

  if (!dispatch)
    {
      dispatch = g_slice_new0 (GMainDispatch);
      g_private_set (&depth_private, dispatch);
    }

  return dispatch;
}

/**
 * g_main_depth:
 *
 * Returns the depth of the stack of calls to
 * g_main_context_dispatch() on any #GMainContext in the current thread.
 *  That is, when called from the toplevel, it gives 0. When
 * called from within a callback from g_main_context_iteration()
 * (or g_main_loop_run(), etc.) it returns 1. When called from within 
 * a callback to a recursive call to g_main_context_iteration(),
 * it returns 2. And so forth.
 *
 * This function is useful in a situation like the following:
 * Imagine an extremely simple "garbage collected" system.
 *
 * |[
 * static GList *free_list;
 * 
 * gpointer
 * allocate_memory (gsize size)
 * { 
 *   gpointer result = g_malloc (size);
 *   free_list = g_list_prepend (free_list, result);
 *   return result;
 * }
 * 
 * void
 * free_allocated_memory (void)
 * {
 *   GList *l;
 *   for (l = free_list; l; l = l->next);
 *     g_free (l->data);
 *   g_list_free (free_list);
 *   free_list = NULL;
 *  }
 * 
 * [...]
 * 
 * while (TRUE); 
 *  {
 *    g_main_context_iteration (NULL, TRUE);
 *    free_allocated_memory();
 *   }
 * ]|
 *
 * This works from an application, however, if you want to do the same
 * thing from a library, it gets more difficult, since you no longer
 * control the main loop. You might think you can simply use an idle
 * function to make the call to free_allocated_memory(), but that
 * doesn't work, since the idle function could be called from a
 * recursive callback. This can be fixed by using g_main_depth()
 *
 * |[
 * gpointer
 * allocate_memory (gsize size)
 * { 
 *   FreeListBlock *block = g_new (FreeListBlock, 1);
 *   block->mem = g_malloc (size);
 *   block->depth = g_main_depth ();   
 *   free_list = g_list_prepend (free_list, block);
 *   return block->mem;
 * }
 * 
 * void
 * free_allocated_memory (void)
 * {
 *   GList *l;
 *   
 *   int depth = g_main_depth ();
 *   for (l = free_list; l; );
 *     {
 *       GList *next = l->next;
 *       FreeListBlock *block = l->data;
 *       if (block->depth > depth)
 *         {
 *           g_free (block->mem);
 *           g_free (block);
 *           free_list = g_list_delete_link (free_list, l);
 *         }
 *               
 *       l = next;
 *     }
 *   }
 * ]|
 *
 * There is a temptation to use g_main_depth() to solve
 * problems with reentrancy. For instance, while waiting for data
 * to be received from the network in response to a menu item,
 * the menu item might be selected again. It might seem that
 * one could make the menu item's callback return immediately
 * and do nothing if g_main_depth() returns a value greater than 1.
 * However, this should be avoided since the user then sees selecting
 * the menu item do nothing. Furthermore, you'll find yourself adding
 * these checks all over your code, since there are doubtless many,
 * many things that the user could do. Instead, you can use the
 * following techniques:
 *
 * <orderedlist>
 *  <listitem>
 *   <para>
 *     Use gtk_widget_set_sensitive() or modal dialogs to prevent
 *     the user from interacting with elements while the main
 *     loop is recursing.
 *   </para>
 *  </listitem>
 *  <listitem>
 *   <para>
 *     Avoid main loop recursion in situations where you can't handle
 *     arbitrary  callbacks. Instead, structure your code so that you
 *     simply return to the main loop and then get called again when
 *     there is more work to do.
 *   </para>
 *  </listitem>
 * </orderedlist>
 * 
 * Return value: The main loop recursion level in the current thread
 **/
int
g_main_depth (void)
{
  GMainDispatch *dispatch = get_dispatch ();
  return dispatch->depth;
}

/**
 * g_main_current_source:
 *
 * Returns the currently firing source for this thread.
 * 
 * Return value: (transfer none): The currently firing source or %NULL.
 *
 * Since: 2.12
 */
GSource *
g_main_current_source (void)
{
  GMainDispatch *dispatch = get_dispatch ();
  return dispatch->dispatching_sources ? dispatch->dispatching_sources->data : NULL;
}

/**
 * g_source_is_destroyed:
 * @source: a #GSource
 *
 * Returns whether @source has been destroyed.
 *
 * This is important when you operate upon your objects 
 * from within idle handlers, but may have freed the object 
 * before the dispatch of your idle handler.
 *
 * |[
 * static gboolean 
 * idle_callback (gpointer data)
 * {
 *   SomeWidget *self = data;
 *    
 *   GDK_THREADS_ENTER (<!-- -->);
 *   /<!-- -->* do stuff with self *<!-- -->/
 *   self->idle_id = 0;
 *   GDK_THREADS_LEAVE (<!-- -->);
 *    
 *   return FALSE;
 * }
 *  
 * static void 
 * some_widget_do_stuff_later (SomeWidget *self)
 * {
 *   self->idle_id = g_idle_add (idle_callback, self);
 * }
 *  
 * static void 
 * some_widget_finalize (GObject *object)
 * {
 *   SomeWidget *self = SOME_WIDGET (object);
 *    
 *   if (self->idle_id)
 *     g_source_remove (self->idle_id);
 *    
 *   G_OBJECT_CLASS (parent_class)->finalize (object);
 * }
 * ]|
 *
 * This will fail in a multi-threaded application if the 
 * widget is destroyed before the idle handler fires due 
 * to the use after free in the callback. A solution, to 
 * this particular problem, is to check to if the source
 * has already been destroy within the callback.
 *
 * |[
 * static gboolean 
 * idle_callback (gpointer data)
 * {
 *   SomeWidget *self = data;
 *   
 *   GDK_THREADS_ENTER ();
 *   if (!g_source_is_destroyed (g_main_current_source ()))
 *     {
 *       /<!-- -->* do stuff with self *<!-- -->/
 *     }
 *   GDK_THREADS_LEAVE ();
 *   
 *   return FALSE;
 * }
 * ]|
 *
 * Return value: %TRUE if the source has been destroyed
 *
 * Since: 2.12
 */
gboolean
g_source_is_destroyed (GSource *source)
{
  return SOURCE_DESTROYED (source);
}

/* Temporarily remove all this source's file descriptors from the
 * poll(), so that if data comes available for one of the file descriptors
 * we don't continually spin in the poll()
 */
/* HOLDS: source->context's lock */
static void
block_source (GSource *source)
{
  GSList *tmp_list;

  g_return_if_fail (!SOURCE_BLOCKED (source));

  tmp_list = source->poll_fds;
  while (tmp_list)
    {
      g_main_context_remove_poll_unlocked (source->context, tmp_list->data);
      tmp_list = tmp_list->next;
    }
}

/* HOLDS: source->context's lock */
static void
unblock_source (GSource *source)
{
  GSList *tmp_list;
  
  g_return_if_fail (!SOURCE_BLOCKED (source)); /* Source already unblocked */
  g_return_if_fail (!SOURCE_DESTROYED (source));
  
  tmp_list = source->poll_fds;
  while (tmp_list)
    {
      g_main_context_add_poll_unlocked (source->context, source->priority, tmp_list->data);
      tmp_list = tmp_list->next;
    }
}

/* HOLDS: context's lock */
static void
g_main_dispatch (GMainContext *context)
{
  GMainDispatch *current = get_dispatch ();
  guint i;

  for (i = 0; i < context->pending_dispatches->len; i++)
    {
      GSource *source = context->pending_dispatches->pdata[i];

      context->pending_dispatches->pdata[i] = NULL;
      g_assert (source);

      source->flags &= ~G_SOURCE_READY;

      if (!SOURCE_DESTROYED (source))
        {
          gboolean was_in_call;
          gpointer user_data = NULL;
          GSourceFunc callback = NULL;
          GSourceCallbackFuncs *cb_funcs;
          gpointer cb_data;
          gboolean need_destroy;

          gboolean (*dispatch) (GSource *,
                                GSourceFunc,
                                gpointer);
          GSList current_source_link;

          dispatch = source->source_funcs->dispatch;
          cb_funcs = source->callback_funcs;
          cb_data = source->callback_data;

          if (cb_funcs)
            cb_funcs->ref (cb_data);
          
          if ((source->flags & G_SOURCE_CAN_RECURSE) == 0)
            block_source (source);
          
          was_in_call = source->flags & G_HOOK_FLAG_IN_CALL;
          source->flags |= G_HOOK_FLAG_IN_CALL;

          if (cb_funcs)
            cb_funcs->get (cb_data, source, &callback, &user_data);

          UNLOCK_CONTEXT (context);

          current->depth++;
          /* The on-stack allocation of the GSList is unconventional, but
           * we know that the lifetime of the link is bounded to this
           * function as the link is kept in a thread specific list and
           * not manipulated outside of this function and its descendants.
           * Avoiding the overhead of a g_slist_alloc() is useful as many
           * applications do little more than dispatch events.
           *
           * This is a performance hack - do not revert to g_slist_prepend()!
           */
          current_source_link.data = source;
          current_source_link.next = current->dispatching_sources;
          current->dispatching_sources = &current_source_link;
          need_destroy = ! dispatch (source,
                                     callback,
                                     user_data);
          g_assert (current->dispatching_sources == &current_source_link);
          current->dispatching_sources = current_source_link.next;
          current->depth--;
          
          if (cb_funcs)
            cb_funcs->unref (cb_data);

          LOCK_CONTEXT (context);
          
          if (!was_in_call)
            source->flags &= ~G_HOOK_FLAG_IN_CALL;

          if ((source->flags & G_SOURCE_CAN_RECURSE) == 0 &&
              !SOURCE_DESTROYED (source))
            unblock_source (source);
          
          /* Note: this depends on the fact that we can't switch
           * sources from one main context to another
           */
          if (need_destroy && !SOURCE_DESTROYED (source))
            {
              g_assert (source->context == context);
              g_source_destroy_internal (source, context, TRUE);
            }
        }
      
      SOURCE_UNREF (source, context);
    }

  g_ptr_array_set_size (context->pending_dispatches, 0);
}

/* Holds context's lock */
static inline GSource *
next_valid_source (GMainContext *context,
                   GSource      *source)
{
  GSource *new_source = source ? source->next : context->source_list;

  while (new_source)
    {
      if (!SOURCE_DESTROYED (new_source))
        {
          new_source->ref_count++;
          break;
        }
      
      new_source = new_source->next;
    }

  if (source)
    SOURCE_UNREF (source, context);
          
  return new_source;
}

/**
 * g_main_context_acquire:
 * @context: a #GMainContext
 * 
 * Tries to become the owner of the specified context.
 * If some other thread is the owner of the context,
 * returns %FALSE immediately. Ownership is properly
 * recursive: the owner can require ownership again
 * and will release ownership when g_main_context_release()
 * is called as many times as g_main_context_acquire().
 *
 * You must be the owner of a context before you
 * can call g_main_context_prepare(), g_main_context_query(),
 * g_main_context_check(), g_main_context_dispatch().
 * 
 * Return value: %TRUE if the operation succeeded, and
 *   this thread is now the owner of @context.
 **/
gboolean 
g_main_context_acquire (GMainContext *context)
{
  gboolean result = FALSE;
  GThread *self = G_THREAD_SELF;

  if (context == NULL)
    context = g_main_context_default ();
  
  LOCK_CONTEXT (context);

  if (!context->owner)
    {
      context->owner = self;
      g_assert (context->owner_count == 0);
    }

  if (context->owner == self)
    {
      context->owner_count++;
      result = TRUE;
    }

  UNLOCK_CONTEXT (context); 
  
  return result;
}

/**
 * g_main_context_release:
 * @context: a #GMainContext
 * 
 * Releases ownership of a context previously acquired by this thread
 * with g_main_context_acquire(). If the context was acquired multiple
 * times, the ownership will be released only when g_main_context_release()
 * is called as many times as it was acquired.
 **/
void
g_main_context_release (GMainContext *context)
{
  if (context == NULL)
    context = g_main_context_default ();
  
  LOCK_CONTEXT (context);

  context->owner_count--;
  if (context->owner_count == 0)
    {
      context->owner = NULL;

      if (context->waiters)
        {
          GMainWaiter *waiter = context->waiters->data;
          gboolean loop_internal_waiter = (waiter->mutex == &context->mutex);
          context->waiters = g_slist_delete_link (context->waiters,
                                                  context->waiters);
          if (!loop_internal_waiter)
            g_mutex_lock (waiter->mutex);
          
          g_cond_signal (waiter->cond);
          
          if (!loop_internal_waiter)
            g_mutex_unlock (waiter->mutex);
        }
    }

  UNLOCK_CONTEXT (context); 
}

/**
 * g_main_context_wait:
 * @context: a #GMainContext
 * @cond: a condition variable
 * @mutex: a mutex, currently held
 * 
 * Tries to become the owner of the specified context,
 * as with g_main_context_acquire(). But if another thread
 * is the owner, atomically drop @mutex and wait on @cond until 
 * that owner releases ownership or until @cond is signaled, then
 * try again (once) to become the owner.
 * 
 * Return value: %TRUE if the operation succeeded, and
 *   this thread is now the owner of @context.
 **/
gboolean
g_main_context_wait (GMainContext *context,
                     GCond        *cond,
                     GMutex       *mutex)
{
  gboolean result = FALSE;
  GThread *self = G_THREAD_SELF;
  gboolean loop_internal_waiter;
  
  if (context == NULL)
    context = g_main_context_default ();

  loop_internal_waiter = (mutex == &context->mutex);
  
  if (!loop_internal_waiter)
    LOCK_CONTEXT (context);

  if (context->owner && context->owner != self)
    {
      GMainWaiter waiter;

      waiter.cond = cond;
      waiter.mutex = mutex;

      context->waiters = g_slist_append (context->waiters, &waiter);
      
      if (!loop_internal_waiter)
        UNLOCK_CONTEXT (context);
      g_cond_wait (cond, mutex);
      if (!loop_internal_waiter)      
        LOCK_CONTEXT (context);

      context->waiters = g_slist_remove (context->waiters, &waiter);
    }

  if (!context->owner)
    {
      context->owner = self;
      g_assert (context->owner_count == 0);
    }

  if (context->owner == self)
    {
      context->owner_count++;
      result = TRUE;
    }

  if (!loop_internal_waiter)
    UNLOCK_CONTEXT (context); 
  
  return result;
}

/**
 * g_main_context_prepare:
 * @context: a #GMainContext
 * @priority: location to store priority of highest priority
 *            source already ready.
 * 
 * Prepares to poll sources within a main loop. The resulting information
 * for polling is determined by calling g_main_context_query ().
 * 
 * Return value: %TRUE if some source is ready to be dispatched
 *               prior to polling.
 **/
gboolean
g_main_context_prepare (GMainContext *context,
                        gint         *priority)
{
  gint i;
  gint n_ready = 0;
  gint current_priority = G_MAXINT;
  GSource *source;

  if (context == NULL)
    context = g_main_context_default ();
  
  LOCK_CONTEXT (context);

  context->time_is_fresh = FALSE;

  if (context->in_check_or_prepare)
    {
      g_warning ("g_main_context_prepare() called recursively from within a source's check() or "
                 "prepare() member.");
      UNLOCK_CONTEXT (context);
      return FALSE;
    }

#if 0
  /* If recursing, finish up current dispatch, before starting over */
  if (context->pending_dispatches)
    {
      if (dispatch)
        g_main_dispatch (context, &current_time);
      
      UNLOCK_CONTEXT (context);
      return TRUE;
    }
#endif

  /* If recursing, clear list of pending dispatches */

  for (i = 0; i < context->pending_dispatches->len; i++)
    {
      if (context->pending_dispatches->pdata[i])
        SOURCE_UNREF ((GSource *)context->pending_dispatches->pdata[i], context);
    }
  g_ptr_array_set_size (context->pending_dispatches, 0);
  
  /* Prepare all sources */

  context->timeout = -1;
  
  source = next_valid_source (context, NULL);
  while (source)
    {
      gint source_timeout = -1;

      if ((n_ready > 0) && (source->priority > current_priority))
        {
          SOURCE_UNREF (source, context);
          break;
        }
      if (SOURCE_BLOCKED (source))
        goto next;

      if (!(source->flags & G_SOURCE_READY))
        {
          gboolean result;
          gboolean (*prepare)  (GSource  *source, 
                                gint     *timeout);

          prepare = source->source_funcs->prepare;
          context->in_check_or_prepare++;
          UNLOCK_CONTEXT (context);

          result = (*prepare) (source, &source_timeout);

          LOCK_CONTEXT (context);
          context->in_check_or_prepare--;

          if (result)
            {
              GSource *ready_source = source;

              while (ready_source)
                {
                  ready_source->flags |= G_SOURCE_READY;
                  ready_source = ready_source->priv ? ready_source->priv->parent_source : NULL;
                }
            }
        }

      if (source->flags & G_SOURCE_READY)
        {
          n_ready++;
          current_priority = source->priority;
          context->timeout = 0;
        }
      
      if (source_timeout >= 0)
        {
          if (context->timeout < 0)
            context->timeout = source_timeout;
          else
            context->timeout = MIN (context->timeout, source_timeout);
        }

    next:
      source = next_valid_source (context, source);
    }

  UNLOCK_CONTEXT (context);
  
  if (priority)
    *priority = current_priority;
  
  return (n_ready > 0);
}

/**
 * g_main_context_query:
 * @context: a #GMainContext
 * @max_priority: maximum priority source to check
 * @timeout_: (out): location to store timeout to be used in polling
 * @fds: (out caller-allocates) (array length=n_fds): location to
 *       store #GPollFD records that need to be polled.
 * @n_fds: length of @fds.
 * 
 * Determines information necessary to poll this main loop.
 * 
 * Return value: the number of records actually stored in @fds,
 *   or, if more than @n_fds records need to be stored, the number
 *   of records that need to be stored.
 **/
gint
g_main_context_query (GMainContext *context,
                      gint          max_priority,
                      gint         *timeout,
                      GPollFD      *fds,
                      gint          n_fds)
{
  gint n_poll;
  GPollRec *pollrec;
  
  LOCK_CONTEXT (context);

  pollrec = context->poll_records;
  n_poll = 0;
  while (pollrec && max_priority >= pollrec->priority)
    {
      /* We need to include entries with fd->events == 0 in the array because
       * otherwise if the application changes fd->events behind our back and 
       * makes it non-zero, we'll be out of sync when we check the fds[] array.
       * (Changing fd->events after adding an FD wasn't an anticipated use of 
       * this API, but it occurs in practice.) */
      if (n_poll < n_fds)
        {
          fds[n_poll].fd = pollrec->fd->fd;
          /* In direct contradiction to the Unix98 spec, IRIX runs into
           * difficulty if you pass in POLLERR, POLLHUP or POLLNVAL
           * flags in the events field of the pollfd while it should
           * just ignoring them. So we mask them out here.
           */
          fds[n_poll].events = pollrec->fd->events & ~(G_IO_ERR|G_IO_HUP|G_IO_NVAL);
          fds[n_poll].revents = 0;
        }

      pollrec = pollrec->next;
      n_poll++;
    }

  context->poll_changed = FALSE;
  
  if (timeout)
    {
      *timeout = context->timeout;
      if (*timeout != 0)
        context->time_is_fresh = FALSE;
    }
  
  UNLOCK_CONTEXT (context);

  return n_poll;
}

/**
 * g_main_context_check:
 * @context: a #GMainContext
 * @max_priority: the maximum numerical priority of sources to check
 * @fds: (array length=n_fds): array of #GPollFD's that was passed to
 *       the last call to g_main_context_query()
 * @n_fds: return value of g_main_context_query()
 * 
 * Passes the results of polling back to the main loop.
 * 
 * Return value: %TRUE if some sources are ready to be dispatched.
 **/
gboolean
g_main_context_check (GMainContext *context,
                      gint          max_priority,
                      GPollFD      *fds,
                      gint          n_fds)
{
  GSource *source;
  GPollRec *pollrec;
  gint n_ready = 0;
  gint i;
   
  LOCK_CONTEXT (context);

  if (context->in_check_or_prepare)
    {
      g_warning ("g_main_context_check() called recursively from within a source's check() or "
                 "prepare() member.");
      UNLOCK_CONTEXT (context);
      return FALSE;
    }

  if (context->wake_up_rec.events)
    g_wakeup_acknowledge (context->wakeup);

  /* If the set of poll file descriptors changed, bail out
   * and let the main loop rerun
   */
  if (context->poll_changed)
    {
      UNLOCK_CONTEXT (context);
      return FALSE;
    }
  
  pollrec = context->poll_records;
  i = 0;
  while (i < n_fds)
    {
      if (pollrec->fd->events)
        pollrec->fd->revents = fds[i].revents;

      pollrec = pollrec->next;
      i++;
    }

  source = next_valid_source (context, NULL);
  while (source)
    {
      if ((n_ready > 0) && (source->priority > max_priority))
        {
          SOURCE_UNREF (source, context);
          break;
        }
      if (SOURCE_BLOCKED (source))
        goto next;

      if (!(source->flags & G_SOURCE_READY))
        {
          gboolean result;
          gboolean (*check) (GSource  *source);

          check = source->source_funcs->check;
          
          context->in_check_or_prepare++;
          UNLOCK_CONTEXT (context);
          
          result = (*check) (source);
          
          LOCK_CONTEXT (context);
          context->in_check_or_prepare--;
          
          if (result)
            {
              GSource *ready_source = source;

              while (ready_source)
                {
                  ready_source->flags |= G_SOURCE_READY;
                  ready_source = ready_source->priv ? ready_source->priv->parent_source : NULL;
                }
            }
        }

      if (source->flags & G_SOURCE_READY)
        {
          source->ref_count++;
          g_ptr_array_add (context->pending_dispatches, source);

          n_ready++;

          /* never dispatch sources with less priority than the first
           * one we choose to dispatch
           */
          max_priority = source->priority;
        }

    next:
      source = next_valid_source (context, source);
    }

  UNLOCK_CONTEXT (context);

  return n_ready > 0;
}

/**
 * g_main_context_dispatch:
 * @context: a #GMainContext
 * 
 * Dispatches all pending sources.
 **/
void
g_main_context_dispatch (GMainContext *context)
{
  LOCK_CONTEXT (context);

  if (context->pending_dispatches->len > 0)
    {
      g_main_dispatch (context);
    }

  UNLOCK_CONTEXT (context);
}

/* HOLDS context lock */
static gboolean
g_main_context_iterate (GMainContext *context,
                        gboolean      block,
                        gboolean      dispatch,
                        GThread      *self)
{
  gint max_priority;
  gint timeout;
  gboolean some_ready;
  gint nfds, allocated_nfds;
  GPollFD *fds = NULL;

  UNLOCK_CONTEXT (context);

  if (!g_main_context_acquire (context))
    {
      gboolean got_ownership;

      LOCK_CONTEXT (context);

      if (!block)
        return FALSE;

      got_ownership = g_main_context_wait (context,
                                           &context->cond,
                                           &context->mutex);

      if (!got_ownership)
        return FALSE;
    }
  else
    LOCK_CONTEXT (context);
  
  if (!context->cached_poll_array)
    {
      context->cached_poll_array_size = context->n_poll_records;
      context->cached_poll_array = g_new (GPollFD, context->n_poll_records);
    }

  allocated_nfds = context->cached_poll_array_size;
  fds = context->cached_poll_array;
  
  UNLOCK_CONTEXT (context);

  g_main_context_prepare (context, &max_priority); 
  
  while ((nfds = g_main_context_query (context, max_priority, &timeout, fds, 
                                       allocated_nfds)) > allocated_nfds)
    {
      LOCK_CONTEXT (context);
      g_free (fds);
      context->cached_poll_array_size = allocated_nfds = nfds;
      context->cached_poll_array = fds = g_new (GPollFD, nfds);
      UNLOCK_CONTEXT (context);
    }

  if (!block)
    timeout = 0;
  
  g_main_context_poll (context, timeout, max_priority, fds, nfds);
  
  some_ready = g_main_context_check (context, max_priority, fds, nfds);
  
  if (dispatch)
    g_main_context_dispatch (context);
  
  g_main_context_release (context);

  LOCK_CONTEXT (context);

  return some_ready;
}

/**
 * g_main_context_pending:
 * @context: a #GMainContext (if %NULL, the default context will be used)
 *
 * Checks if any sources have pending events for the given context.
 * 
 * Return value: %TRUE if events are pending.
 **/
gboolean 
g_main_context_pending (GMainContext *context)
{
  gboolean retval;

  if (!context)
    context = g_main_context_default();

  LOCK_CONTEXT (context);
  retval = g_main_context_iterate (context, FALSE, FALSE, G_THREAD_SELF);
  UNLOCK_CONTEXT (context);
  
  return retval;
}

/**
 * g_main_context_iteration:
 * @context: a #GMainContext (if %NULL, the default context will be used) 
 * @may_block: whether the call may block.
 * 
 * Runs a single iteration for the given main loop. This involves
 * checking to see if any event sources are ready to be processed,
 * then if no events sources are ready and @may_block is %TRUE, waiting
 * for a source to become ready, then dispatching the highest priority
 * events sources that are ready. Otherwise, if @may_block is %FALSE 
 * sources are not waited to become ready, only those highest priority 
 * events sources will be dispatched (if any), that are ready at this 
 * given moment without further waiting.
 *
 * Note that even when @may_block is %TRUE, it is still possible for 
 * g_main_context_iteration() to return %FALSE, since the the wait may 
 * be interrupted for other reasons than an event source becoming ready.
 * 
 * Return value: %TRUE if events were dispatched.
 **/
gboolean
g_main_context_iteration (GMainContext *context, gboolean may_block)
{
  gboolean retval;

  if (!context)
    context = g_main_context_default();
  
  LOCK_CONTEXT (context);
  retval = g_main_context_iterate (context, may_block, TRUE, G_THREAD_SELF);
  UNLOCK_CONTEXT (context);
  
  return retval;
}

/**
 * g_main_loop_new:
 * @context: (allow-none): a #GMainContext  (if %NULL, the default context will be used).
 * @is_running: set to %TRUE to indicate that the loop is running. This
 * is not very important since calling g_main_loop_run() will set this to
 * %TRUE anyway.
 * 
 * Creates a new #GMainLoop structure.
 * 
 * Return value: a new #GMainLoop.
 **/
GMainLoop *
g_main_loop_new (GMainContext *context,
                 gboolean      is_running)
{
  GMainLoop *loop;

  if (!context)
    context = g_main_context_default();
  
  g_main_context_ref (context);

  loop = g_new0 (GMainLoop, 1);
  loop->context = context;
  loop->is_running = is_running != FALSE;
  loop->ref_count = 1;
  
  return loop;
}

/**
 * g_main_loop_ref:
 * @loop: a #GMainLoop
 * 
 * Increases the reference count on a #GMainLoop object by one.
 * 
 * Return value: @loop
 **/
GMainLoop *
g_main_loop_ref (GMainLoop *loop)
{
  g_return_val_if_fail (loop != NULL, NULL);
  g_return_val_if_fail (g_atomic_int_get (&loop->ref_count) > 0, NULL);

  g_atomic_int_inc (&loop->ref_count);

  return loop;
}

/**
 * g_main_loop_unref:
 * @loop: a #GMainLoop
 * 
 * Decreases the reference count on a #GMainLoop object by one. If
 * the result is zero, free the loop and free all associated memory.
 **/
void
g_main_loop_unref (GMainLoop *loop)
{
  g_return_if_fail (loop != NULL);
  g_return_if_fail (g_atomic_int_get (&loop->ref_count) > 0);

  if (!g_atomic_int_dec_and_test (&loop->ref_count))
    return;

  g_main_context_unref (loop->context);
  g_free (loop);
}

/**
 * g_main_loop_run:
 * @loop: a #GMainLoop
 * 
 * Runs a main loop until g_main_loop_quit() is called on the loop.
 * If this is called for the thread of the loop's #GMainContext,
 * it will process events from the loop, otherwise it will
 * simply wait.
 **/
void 
g_main_loop_run (GMainLoop *loop)
{
  GThread *self = G_THREAD_SELF;

  g_return_if_fail (loop != NULL);
  g_return_if_fail (g_atomic_int_get (&loop->ref_count) > 0);

  if (!g_main_context_acquire (loop->context))
    {
      gboolean got_ownership = FALSE;
      
      /* Another thread owns this context */
      LOCK_CONTEXT (loop->context);

      g_atomic_int_inc (&loop->ref_count);

      if (!loop->is_running)
        loop->is_running = TRUE;

      while (loop->is_running && !got_ownership)
        got_ownership = g_main_context_wait (loop->context,
                                             &loop->context->cond,
                                             &loop->context->mutex);
      
      if (!loop->is_running)
        {
          UNLOCK_CONTEXT (loop->context);
          if (got_ownership)
            g_main_context_release (loop->context);
          g_main_loop_unref (loop);
          return;
        }

      g_assert (got_ownership);
    }
  else
    LOCK_CONTEXT (loop->context);

  if (loop->context->in_check_or_prepare)
    {
      g_warning ("g_main_loop_run(): called recursively from within a source's "
                 "check() or prepare() member, iteration not possible.");
      return;
    }

  g_atomic_int_inc (&loop->ref_count);
  loop->is_running = TRUE;
  while (loop->is_running)
    g_main_context_iterate (loop->context, TRUE, TRUE, self);

  UNLOCK_CONTEXT (loop->context);
  
  g_main_context_release (loop->context);
  
  g_main_loop_unref (loop);
}

/**
 * g_main_loop_quit:
 * @loop: a #GMainLoop
 * 
 * Stops a #GMainLoop from running. Any calls to g_main_loop_run()
 * for the loop will return. 
 *
 * Note that sources that have already been dispatched when 
 * g_main_loop_quit() is called will still be executed.
 **/
void 
g_main_loop_quit (GMainLoop *loop)
{
  g_return_if_fail (loop != NULL);
  g_return_if_fail (g_atomic_int_get (&loop->ref_count) > 0);

  LOCK_CONTEXT (loop->context);
  loop->is_running = FALSE;
  g_wakeup_signal (loop->context->wakeup);

  g_cond_broadcast (&loop->context->cond);

  UNLOCK_CONTEXT (loop->context);
}

/**
 * g_main_loop_is_running:
 * @loop: a #GMainLoop.
 * 
 * Checks to see if the main loop is currently being run via g_main_loop_run().
 * 
 * Return value: %TRUE if the mainloop is currently being run.
 **/
gboolean
g_main_loop_is_running (GMainLoop *loop)
{
  g_return_val_if_fail (loop != NULL, FALSE);
  g_return_val_if_fail (g_atomic_int_get (&loop->ref_count) > 0, FALSE);

  return loop->is_running;
}

/**
 * g_main_loop_get_context:
 * @loop: a #GMainLoop.
 * 
 * Returns the #GMainContext of @loop.
 * 
 * Return value: (transfer none): the #GMainContext of @loop
 **/
GMainContext *
g_main_loop_get_context (GMainLoop *loop)
{
  g_return_val_if_fail (loop != NULL, NULL);
  g_return_val_if_fail (g_atomic_int_get (&loop->ref_count) > 0, NULL);
 
  return loop->context;
}

/* HOLDS: context's lock */
static void
g_main_context_poll (GMainContext *context,
                     gint          timeout,
                     gint          priority,
                     GPollFD      *fds,
                     gint          n_fds)
{
#ifdef  G_MAIN_POLL_DEBUG
  GTimer *poll_timer;
  GPollRec *pollrec;
  gint i;
#endif

  GPollFunc poll_func;

  if (n_fds || timeout != 0)
    {
#ifdef  G_MAIN_POLL_DEBUG
      if (_g_main_poll_debug)
        {
          g_print ("polling context=%p n=%d timeout=%d\n",
                   context, n_fds, timeout);
          poll_timer = g_timer_new ();
        }
#endif

      LOCK_CONTEXT (context);

      poll_func = context->poll_func;
      
      UNLOCK_CONTEXT (context);
      if ((*poll_func) (fds, n_fds, timeout) < 0 && errno != EINTR)
        {
#ifndef G_OS_WIN32
          g_warning ("poll(2) failed due to: %s.",
                     g_strerror (errno));
#else
          /* If g_poll () returns -1, it has already called g_warning() */
#endif
        }
      
#ifdef  G_MAIN_POLL_DEBUG
      if (_g_main_poll_debug)
        {
          LOCK_CONTEXT (context);

          g_print ("g_main_poll(%d) timeout: %d - elapsed %12.10f seconds",
                   n_fds,
                   timeout,
                   g_timer_elapsed (poll_timer, NULL));
          g_timer_destroy (poll_timer);
          pollrec = context->poll_records;

          while (pollrec != NULL)
            {
              i = 0;
              while (i < n_fds)
                {
                  if (fds[i].fd == pollrec->fd->fd &&
                      pollrec->fd->events &&
                      fds[i].revents)
                    {
                      g_print (" [" G_POLLFD_FORMAT " :", fds[i].fd);
                      if (fds[i].revents & G_IO_IN)
                        g_print ("i");
                      if (fds[i].revents & G_IO_OUT)
                        g_print ("o");
                      if (fds[i].revents & G_IO_PRI)
                        g_print ("p");
                      if (fds[i].revents & G_IO_ERR)
                        g_print ("e");
                      if (fds[i].revents & G_IO_HUP)
                        g_print ("h");
                      if (fds[i].revents & G_IO_NVAL)
                        g_print ("n");
                      g_print ("]");
                    }
                  i++;
                }
              pollrec = pollrec->next;
            }
          g_print ("\n");

          UNLOCK_CONTEXT (context);
        }
#endif
    } /* if (n_fds || timeout != 0) */
}

/**
 * g_main_context_add_poll:
 * @context: a #GMainContext (or %NULL for the default context)
 * @fd: a #GPollFD structure holding information about a file
 *      descriptor to watch.
 * @priority: the priority for this file descriptor which should be
 *      the same as the priority used for g_source_attach() to ensure that the
 *      file descriptor is polled whenever the results may be needed.
 * 
 * Adds a file descriptor to the set of file descriptors polled for
 * this context. This will very seldom be used directly. Instead
 * a typical event source will use g_source_add_poll() instead.
 **/
void
g_main_context_add_poll (GMainContext *context,
                         GPollFD      *fd,
                         gint          priority)
{
  if (!context)
    context = g_main_context_default ();
  
  g_return_if_fail (g_atomic_int_get (&context->ref_count) > 0);
  g_return_if_fail (fd);

  LOCK_CONTEXT (context);
  g_main_context_add_poll_unlocked (context, priority, fd);
  UNLOCK_CONTEXT (context);
}

/* HOLDS: main_loop_lock */
static void 
g_main_context_add_poll_unlocked (GMainContext *context,
                                  gint          priority,
                                  GPollFD      *fd)
{
  GPollRec *prevrec, *nextrec;
  GPollRec *newrec = g_slice_new (GPollRec);

  /* This file descriptor may be checked before we ever poll */
  fd->revents = 0;
  newrec->fd = fd;
  newrec->priority = priority;

  prevrec = context->poll_records_tail;
  nextrec = NULL;
  while (prevrec && priority < prevrec->priority)
    {
      nextrec = prevrec;
      prevrec = prevrec->prev;
    }

  if (prevrec)
    prevrec->next = newrec;
  else
    context->poll_records = newrec;

  newrec->prev = prevrec;
  newrec->next = nextrec;

  if (nextrec)
    nextrec->prev = newrec;
  else 
    context->poll_records_tail = newrec;

  context->n_poll_records++;

  context->poll_changed = TRUE;

  /* Now wake up the main loop if it is waiting in the poll() */
  g_wakeup_signal (context->wakeup);
}

/**
 * g_main_context_remove_poll:
 * @context:a #GMainContext 
 * @fd: a #GPollFD descriptor previously added with g_main_context_add_poll()
 * 
 * Removes file descriptor from the set of file descriptors to be
 * polled for a particular context.
 **/
void
g_main_context_remove_poll (GMainContext *context,
                            GPollFD      *fd)
{
  if (!context)
    context = g_main_context_default ();
  
  g_return_if_fail (g_atomic_int_get (&context->ref_count) > 0);
  g_return_if_fail (fd);

  LOCK_CONTEXT (context);
  g_main_context_remove_poll_unlocked (context, fd);
  UNLOCK_CONTEXT (context);
}

static void
g_main_context_remove_poll_unlocked (GMainContext *context,
                                     GPollFD      *fd)
{
  GPollRec *pollrec, *prevrec, *nextrec;

  prevrec = NULL;
  pollrec = context->poll_records;

  while (pollrec)
    {
      nextrec = pollrec->next;
      if (pollrec->fd == fd)
        {
          if (prevrec != NULL)
            prevrec->next = nextrec;
          else
            context->poll_records = nextrec;

          if (nextrec != NULL)
            nextrec->prev = prevrec;
          else
            context->poll_records_tail = prevrec;

          g_slice_free (GPollRec, pollrec);

          context->n_poll_records--;
          break;
        }
      prevrec = pollrec;
      pollrec = nextrec;
    }

  context->poll_changed = TRUE;
  
  /* Now wake up the main loop if it is waiting in the poll() */
  g_wakeup_signal (context->wakeup);
}

/**
 * g_source_get_current_time:
 * @source:  a #GSource
 * @timeval: #GTimeVal structure in which to store current time.
 *
 * This function ignores @source and is otherwise the same as
 * g_get_current_time().
 *
 * Deprecated: 2.28: use g_source_get_time() instead
 **/
void
g_source_get_current_time (GSource  *source,
                           GTimeVal *timeval)
{
  g_get_current_time (timeval);
}

/**
 * g_source_get_time:
 * @source: a #GSource
 *
 * Gets the time to be used when checking this source. The advantage of
 * calling this function over calling g_get_monotonic_time() directly is
 * that when checking multiple sources, GLib can cache a single value
 * instead of having to repeatedly get the system monotonic time.
 *
 * The time here is the system monotonic time, if available, or some
 * other reasonable alternative otherwise.  See g_get_monotonic_time().
 *
 * Returns: the monotonic time in microseconds
 *
 * Since: 2.28
 **/
gint64
g_source_get_time (GSource *source)
{
  GMainContext *context;
  gint64 result;

  g_return_val_if_fail (source->context != NULL, 0);

  context = source->context;

  LOCK_CONTEXT (context);

  if (!context->time_is_fresh)
    {
      context->time = g_get_monotonic_time ();
      context->time_is_fresh = TRUE;
    }

  result = context->time;

  UNLOCK_CONTEXT (context);

  return result;
}

/**
 * g_main_context_set_poll_func:
 * @context: a #GMainContext
 * @func: the function to call to poll all file descriptors
 * 
 * Sets the function to use to handle polling of file descriptors. It
 * will be used instead of the poll() system call 
 * (or GLib's replacement function, which is used where 
 * poll() isn't available).
 *
 * This function could possibly be used to integrate the GLib event
 * loop with an external event loop.
 **/
void
g_main_context_set_poll_func (GMainContext *context,
                              GPollFunc     func)
{
  if (!context)
    context = g_main_context_default ();
  
  g_return_if_fail (g_atomic_int_get (&context->ref_count) > 0);

  LOCK_CONTEXT (context);
  
  if (func)
    context->poll_func = func;
  else
    context->poll_func = g_poll;

  UNLOCK_CONTEXT (context);
}

/**
 * g_main_context_get_poll_func:
 * @context: a #GMainContext
 * 
 * Gets the poll function set by g_main_context_set_poll_func().
 * 
 * Return value: the poll function
 **/
GPollFunc
g_main_context_get_poll_func (GMainContext *context)
{
  GPollFunc result;
  
  if (!context)
    context = g_main_context_default ();
  
  g_return_val_if_fail (g_atomic_int_get (&context->ref_count) > 0, NULL);

  LOCK_CONTEXT (context);
  result = context->poll_func;
  UNLOCK_CONTEXT (context);

  return result;
}

/**
 * g_main_context_wakeup:
 * @context: a #GMainContext
 * 
 * If @context is currently waiting in a poll(), interrupt
 * the poll(), and continue the iteration process.
 **/
void
g_main_context_wakeup (GMainContext *context)
{
  if (!context)
    context = g_main_context_default ();

  g_return_if_fail (g_atomic_int_get (&context->ref_count) > 0);

  g_wakeup_signal (context->wakeup);
}

/**
 * g_main_context_is_owner:
 * @context: a #GMainContext
 * 
 * Determines whether this thread holds the (recursive)
 * ownership of this #GMainContext. This is useful to
 * know before waiting on another thread that may be
 * blocking to get ownership of @context.
 *
 * Returns: %TRUE if current thread is owner of @context.
 *
 * Since: 2.10
 **/
gboolean
g_main_context_is_owner (GMainContext *context)
{
  gboolean is_owner;

  if (!context)
    context = g_main_context_default ();

  LOCK_CONTEXT (context);
  is_owner = context->owner == G_THREAD_SELF;
  UNLOCK_CONTEXT (context);

  return is_owner;
}

/* Timeouts */

static void
g_timeout_set_expiration (GTimeoutSource *timeout_source,
                          gint64          current_time)
{
  timeout_source->expiration = current_time +
                               (guint64) timeout_source->interval * 1000;

  if (timeout_source->seconds)
    {
      gint64 remainder;
      static gint timer_perturb = -1;

      if (timer_perturb == -1)
        {
          /*
           * we want a per machine/session unique 'random' value; try the dbus
           * address first, that has a UUID in it. If there is no dbus, use the
           * hostname for hashing.
           */
          const char *session_bus_address = g_getenv ("DBUS_SESSION_BUS_ADDRESS");
          if (!session_bus_address)
            session_bus_address = g_getenv ("HOSTNAME");
          if (session_bus_address)
            timer_perturb = ABS ((gint) g_str_hash (session_bus_address)) % 1000000;
          else
            timer_perturb = 0;
        }

      /* We want the microseconds part of the timeout to land on the
       * 'timer_perturb' mark, but we need to make sure we don't try to
       * set the timeout in the past.  We do this by ensuring that we
       * always only *increase* the expiration time by adding a full
       * second in the case that the microsecond portion decreases.
       */
      timeout_source->expiration -= timer_perturb;

      remainder = timeout_source->expiration % 1000000;
      if (remainder >= 1000000/4)
        timeout_source->expiration += 1000000;

      timeout_source->expiration -= remainder;
      timeout_source->expiration += timer_perturb;
    }
}

static gboolean
g_timeout_prepare (GSource *source,
                   gint    *timeout)
{
  GTimeoutSource *timeout_source = (GTimeoutSource *) source;
  gint64 now = g_source_get_time (source);

  if (now < timeout_source->expiration)
    {
      /* Round up to ensure that we don't try again too early */
      *timeout = (timeout_source->expiration - now + 999) / 1000;
      return FALSE;
    }

  *timeout = 0;
  return TRUE;
}

static gboolean 
g_timeout_check (GSource *source)
{
  GTimeoutSource *timeout_source = (GTimeoutSource *) source;
  gint64 now = g_source_get_time (source);

  return timeout_source->expiration <= now;
}

static gboolean
g_timeout_dispatch (GSource     *source,
                    GSourceFunc  callback,
                    gpointer     user_data)
{
  GTimeoutSource *timeout_source = (GTimeoutSource *)source;
  gboolean again;

  if (!callback)
    {
      g_warning ("Timeout source dispatched without callback\n"
                 "You must call g_source_set_callback().");
      return FALSE;
    }

  again = callback (user_data);

  if (again)
    g_timeout_set_expiration (timeout_source, g_source_get_time (source));

  return again;
}

/**
 * g_timeout_source_new:
 * @interval: the timeout interval in milliseconds.
 * 
 * Creates a new timeout source.
 *
 * The source will not initially be associated with any #GMainContext
 * and must be added to one with g_source_attach() before it will be
 * executed.
 *
 * The interval given is in terms of monotonic time, not wall clock
 * time.  See g_get_monotonic_time().
 * 
 * Return value: the newly-created timeout source
 **/
GSource *
g_timeout_source_new (guint interval)
{
  GSource *source = g_source_new (&g_timeout_funcs, sizeof (GTimeoutSource));
  GTimeoutSource *timeout_source = (GTimeoutSource *)source;

  timeout_source->interval = interval;
  g_timeout_set_expiration (timeout_source, g_get_monotonic_time ());

  return source;
}

/**
 * g_timeout_source_new_seconds:
 * @interval: the timeout interval in seconds
 *
 * Creates a new timeout source.
 *
 * The source will not initially be associated with any #GMainContext
 * and must be added to one with g_source_attach() before it will be
 * executed.
 *
 * The scheduling granularity/accuracy of this timeout source will be
 * in seconds.
 *
 * The interval given in terms of monotonic time, not wall clock time.
 * See g_get_monotonic_time().
 *
 * Return value: the newly-created timeout source
 *
 * Since: 2.14  
 **/
GSource *
g_timeout_source_new_seconds (guint interval)
{
  GSource *source = g_source_new (&g_timeout_funcs, sizeof (GTimeoutSource));
  GTimeoutSource *timeout_source = (GTimeoutSource *)source;

  timeout_source->interval = 1000 * interval;
  timeout_source->seconds = TRUE;

  g_timeout_set_expiration (timeout_source, g_get_monotonic_time ());

  return source;
}


/**
 * g_timeout_add_full:
 * @priority: the priority of the timeout source. Typically this will be in
 *            the range between #G_PRIORITY_DEFAULT and #G_PRIORITY_HIGH.
 * @interval: the time between calls to the function, in milliseconds
 *             (1/1000ths of a second)
 * @function: function to call
 * @data:     data to pass to @function
 * @notify:   function to call when the timeout is removed, or %NULL
 * 
 * Sets a function to be called at regular intervals, with the given
 * priority.  The function is called repeatedly until it returns
 * %FALSE, at which point the timeout is automatically destroyed and
 * the function will not be called again.  The @notify function is
 * called when the timeout is destroyed.  The first call to the
 * function will be at the end of the first @interval.
 *
 * Note that timeout functions may be delayed, due to the processing of other
 * event sources. Thus they should not be relied on for precise timing.
 * After each call to the timeout function, the time of the next
 * timeout is recalculated based on the current time and the given interval
 * (it does not try to 'catch up' time lost in delays).
 *
 * This internally creates a main loop source using g_timeout_source_new()
 * and attaches it to the main loop context using g_source_attach(). You can
 * do these steps manually if you need greater control.
 *
 * The interval given in terms of monotonic time, not wall clock time.
 * See g_get_monotonic_time().
 * 
 * Return value: the ID (greater than 0) of the event source.
 * Rename to: g_timeout_add
 **/
guint
g_timeout_add_full (gint           priority,
                    guint          interval,
                    GSourceFunc    function,
                    gpointer       data,
                    GDestroyNotify notify)
{
  GSource *source;
  guint id;
  
  g_return_val_if_fail (function != NULL, 0);

  source = g_timeout_source_new (interval);

  if (priority != G_PRIORITY_DEFAULT)
    g_source_set_priority (source, priority);

  g_source_set_callback (source, function, data, notify);
  id = g_source_attach (source, NULL);
  g_source_unref (source);

  return id;
}

/**
 * g_timeout_add:
 * @interval: the time between calls to the function, in milliseconds
 *             (1/1000ths of a second)
 * @function: function to call
 * @data:     data to pass to @function
 * 
 * Sets a function to be called at regular intervals, with the default
 * priority, #G_PRIORITY_DEFAULT.  The function is called repeatedly
 * until it returns %FALSE, at which point the timeout is automatically
 * destroyed and the function will not be called again.  The first call
 * to the function will be at the end of the first @interval.
 *
 * Note that timeout functions may be delayed, due to the processing of other
 * event sources. Thus they should not be relied on for precise timing.
 * After each call to the timeout function, the time of the next
 * timeout is recalculated based on the current time and the given interval
 * (it does not try to 'catch up' time lost in delays).
 *
 * If you want to have a timer in the "seconds" range and do not care
 * about the exact time of the first call of the timer, use the
 * g_timeout_add_seconds() function; this function allows for more
 * optimizations and more efficient system power usage.
 *
 * This internally creates a main loop source using g_timeout_source_new()
 * and attaches it to the main loop context using g_source_attach(). You can
 * do these steps manually if you need greater control.
 * 
 * The interval given is in terms of monotonic time, not wall clock
 * time.  See g_get_monotonic_time().
 * 
 * Return value: the ID (greater than 0) of the event source.
 **/
guint
g_timeout_add (guint32        interval,
               GSourceFunc    function,
               gpointer       data)
{
  return g_timeout_add_full (G_PRIORITY_DEFAULT, 
                             interval, function, data, NULL);
}

/**
 * g_timeout_add_seconds_full:
 * @priority: the priority of the timeout source. Typically this will be in
 *            the range between #G_PRIORITY_DEFAULT and #G_PRIORITY_HIGH.
 * @interval: the time between calls to the function, in seconds
 * @function: function to call
 * @data:     data to pass to @function
 * @notify:   function to call when the timeout is removed, or %NULL
 *
 * Sets a function to be called at regular intervals, with @priority.
 * The function is called repeatedly until it returns %FALSE, at which
 * point the timeout is automatically destroyed and the function will
 * not be called again.
 *
 * Unlike g_timeout_add(), this function operates at whole second granularity.
 * The initial starting point of the timer is determined by the implementation
 * and the implementation is expected to group multiple timers together so that
 * they fire all at the same time.
 * To allow this grouping, the @interval to the first timer is rounded
 * and can deviate up to one second from the specified interval.
 * Subsequent timer iterations will generally run at the specified interval.
 *
 * Note that timeout functions may be delayed, due to the processing of other
 * event sources. Thus they should not be relied on for precise timing.
 * After each call to the timeout function, the time of the next
 * timeout is recalculated based on the current time and the given @interval
 *
 * If you want timing more precise than whole seconds, use g_timeout_add()
 * instead.
 *
 * The grouping of timers to fire at the same time results in a more power
 * and CPU efficient behavior so if your timer is in multiples of seconds
 * and you don't require the first timer exactly one second from now, the
 * use of g_timeout_add_seconds() is preferred over g_timeout_add().
 *
 * This internally creates a main loop source using 
 * g_timeout_source_new_seconds() and attaches it to the main loop context 
 * using g_source_attach(). You can do these steps manually if you need 
 * greater control.
 * 
 * The interval given is in terms of monotonic time, not wall clock
 * time.  See g_get_monotonic_time().
 * 
 * Return value: the ID (greater than 0) of the event source.
 *
 * Rename to: g_timeout_add_seconds
 * Since: 2.14
 **/
guint
g_timeout_add_seconds_full (gint           priority,
                            guint32        interval,
                            GSourceFunc    function,
                            gpointer       data,
                            GDestroyNotify notify)
{
  GSource *source;
  guint id;

  g_return_val_if_fail (function != NULL, 0);

  source = g_timeout_source_new_seconds (interval);

  if (priority != G_PRIORITY_DEFAULT)
    g_source_set_priority (source, priority);

  g_source_set_callback (source, function, data, notify);
  id = g_source_attach (source, NULL);
  g_source_unref (source);

  return id;
}

/**
 * g_timeout_add_seconds:
 * @interval: the time between calls to the function, in seconds
 * @function: function to call
 * @data: data to pass to @function
 *
 * Sets a function to be called at regular intervals with the default
 * priority, #G_PRIORITY_DEFAULT. The function is called repeatedly until
 * it returns %FALSE, at which point the timeout is automatically destroyed
 * and the function will not be called again.
 *
 * This internally creates a main loop source using
 * g_timeout_source_new_seconds() and attaches it to the main loop context
 * using g_source_attach(). You can do these steps manually if you need
 * greater control. Also see g_timeout_add_seconds_full().
 *
 * Note that the first call of the timer may not be precise for timeouts
 * of one second. If you need finer precision and have such a timeout,
 * you may want to use g_timeout_add() instead.
 *
 * The interval given is in terms of monotonic time, not wall clock
 * time.  See g_get_monotonic_time().
 * 
 * Return value: the ID (greater than 0) of the event source.
 *
 * Since: 2.14
 **/
guint
g_timeout_add_seconds (guint       interval,
                       GSourceFunc function,
                       gpointer    data)
{
  g_return_val_if_fail (function != NULL, 0);

  return g_timeout_add_seconds_full (G_PRIORITY_DEFAULT, interval, function, data, NULL);
}

/* Child watch functions */

#ifdef G_OS_WIN32

static gboolean
g_child_watch_prepare (GSource *source,
                       gint    *timeout)
{
  *timeout = -1;
  return FALSE;
}

static gboolean 
g_child_watch_check (GSource  *source)
{
  GChildWatchSource *child_watch_source;
  gboolean child_exited;

  child_watch_source = (GChildWatchSource *) source;

  child_exited = child_watch_source->poll.revents & G_IO_IN;

  if (child_exited)
    {
      DWORD child_status;

      /*
       * Note: We do _not_ check for the special value of STILL_ACTIVE
       * since we know that the process has exited and doing so runs into
       * problems if the child process "happens to return STILL_ACTIVE(259)"
       * as Microsoft's Platform SDK puts it.
       */
      if (!GetExitCodeProcess (child_watch_source->pid, &child_status))
        {
          gchar *emsg = g_win32_error_message (GetLastError ());
          g_warning (G_STRLOC ": GetExitCodeProcess() failed: %s", emsg);
          g_free (emsg);

          child_watch_source->child_status = -1;
        }
      else
        child_watch_source->child_status = child_status;
    }

  return child_exited;
}

static void
g_child_watch_finalize (GSource *source)
{
}

#else /* G_OS_WIN32 */

static void
wake_source (GSource *source)
{
  GMainContext *context;

  /* This should be thread-safe:
   *
   *  - if the source is currently being added to a context, that
   *    context will be woken up anyway
   *
   *  - if the source is currently being destroyed, we simply need not
   *    to crash:
   *
   *    - the memory for the source will remain valid until after the
   *      source finalize function was called (which would remove the
   *      source from the global list which we are currently holding the
   *      lock for)
   *
   *    - the GMainContext will either be NULL or point to a live
   *      GMainContext
   *
   *    - the GMainContext will remain valid since we hold the
   *      main_context_list lock
   *
   *  Since we are holding a lot of locks here, don't try to enter any
   *  more GMainContext functions for fear of dealock -- just hit the
   *  GWakeup and run.  Even if that's safe now, it could easily become
   *  unsafe with some very minor changes in the future, and signal
   *  handling is not the most well-tested codepath.
   */
  G_LOCK(main_context_list);
  context = source->context;
  if (context)
    g_wakeup_signal (context->wakeup);
  G_UNLOCK(main_context_list);
}

static void
dispatch_unix_signals (void)
{
  GSList *node;

  /* clear this first incase another one arrives while we're processing */
  any_unix_signal_pending = FALSE;

  G_LOCK(unix_signal_lock);

  /* handle GChildWatchSource instances */
  if (unix_signal_pending[SIGCHLD])
    {
      unix_signal_pending[SIGCHLD] = FALSE;

      /* The only way we can do this is to scan all of the children.
       *
       * The docs promise that we will not reap children that we are not
       * explicitly watching, so that ties our hands from calling
       * waitpid(-1).  We also can't use siginfo's si_pid field since if
       * multiple SIGCHLD arrive at the same time, one of them can be
       * dropped (since a given UNIX signal can only be pending once).
       */
      for (node = unix_child_watches; node; node = node->next)
        {
          GChildWatchSource *source = node->data;

          if (!source->child_exited)
            {
              if (waitpid (source->pid, &source->child_status, WNOHANG) > 0)
                {
                  source->child_exited = TRUE;

                  wake_source ((GSource *) source);
                }
            }
        }
    }

  /* handle GUnixSignalWatchSource instances */
  for (node = unix_signal_watches; node; node = node->next)
    {
      GUnixSignalWatchSource *source = node->data;

      if (!source->pending)
        {
          if (unix_signal_pending[source->signum])
            {
              unix_signal_pending[source->signum] = FALSE;
              source->pending = TRUE;

              wake_source ((GSource *) source);
            }
        }
    }

  G_UNLOCK(unix_signal_lock);
}

static gboolean
g_child_watch_prepare (GSource *source,
                       gint    *timeout)
{
  GChildWatchSource *child_watch_source;

  child_watch_source = (GChildWatchSource *) source;

  return child_watch_source->child_exited;
}

static gboolean
g_child_watch_check (GSource *source)
{
  GChildWatchSource *child_watch_source;

  child_watch_source = (GChildWatchSource *) source;

  return child_watch_source->child_exited;
}

static gboolean
g_unix_signal_watch_prepare (GSource *source,
                             gint    *timeout)
{
  GUnixSignalWatchSource *unix_signal_source;

  unix_signal_source = (GUnixSignalWatchSource *) source;

  return unix_signal_source->pending;
}

static gboolean
g_unix_signal_watch_check (GSource  *source)
{
  GUnixSignalWatchSource *unix_signal_source;

  unix_signal_source = (GUnixSignalWatchSource *) source;

  return unix_signal_source->pending;
}

static gboolean
g_unix_signal_watch_dispatch (GSource    *source, 
                              GSourceFunc callback,
                              gpointer    user_data)
{
  GUnixSignalWatchSource *unix_signal_source;

  unix_signal_source = (GUnixSignalWatchSource *) source;

  if (!callback)
    {
      g_warning ("Unix signal source dispatched without callback\n"
                 "You must call g_source_set_callback().");
      return FALSE;
    }

  (callback) (user_data);

  unix_signal_source->pending = FALSE;

  return TRUE;
}

static void
ensure_unix_signal_handler_installed_unlocked (int signum)
{
  static sigset_t installed_signal_mask;
  static gboolean initialized;
  struct sigaction action;

  if (!initialized)
    {
      sigemptyset (&installed_signal_mask);
      g_get_worker_context ();
      initialized = TRUE;
    }

  if (sigismember (&installed_signal_mask, signum))
    return;

  sigaddset (&installed_signal_mask, signum);

  action.sa_handler = g_unix_signal_handler;
  sigemptyset (&action.sa_mask);
  action.sa_flags = SA_RESTART | SA_NOCLDSTOP;
  sigaction (signum, &action, NULL);
}

GSource *
_g_main_create_unix_signal_watch (int signum)
{
  GSource *source;
  GUnixSignalWatchSource *unix_signal_source;

  source = g_source_new (&g_unix_signal_funcs, sizeof (GUnixSignalWatchSource));
  unix_signal_source = (GUnixSignalWatchSource *) source;

  unix_signal_source->signum = signum;
  unix_signal_source->pending = FALSE;

  G_LOCK (unix_signal_lock);
  ensure_unix_signal_handler_installed_unlocked (signum);
  unix_signal_watches = g_slist_prepend (unix_signal_watches, unix_signal_source);
  if (unix_signal_pending[signum])
    unix_signal_source->pending = TRUE;
  unix_signal_pending[signum] = FALSE;
  G_UNLOCK (unix_signal_lock);

  return source;
}

static void
g_unix_signal_watch_finalize (GSource    *source)
{
  G_LOCK (unix_signal_lock);
  unix_signal_watches = g_slist_remove (unix_signal_watches, source);
  G_UNLOCK (unix_signal_lock);
}

static void
g_child_watch_finalize (GSource *source)
{
  G_LOCK (unix_signal_lock);
  unix_child_watches = g_slist_remove (unix_child_watches, source);
  G_UNLOCK (unix_signal_lock);
}

#endif /* G_OS_WIN32 */

static gboolean
g_child_watch_dispatch (GSource    *source, 
                        GSourceFunc callback,
                        gpointer    user_data)
{
  GChildWatchSource *child_watch_source;
  GChildWatchFunc child_watch_callback = (GChildWatchFunc) callback;

  child_watch_source = (GChildWatchSource *) source;

  if (!callback)
    {
      g_warning ("Child watch source dispatched without callback\n"
                 "You must call g_source_set_callback().");
      return FALSE;
    }

  (child_watch_callback) (child_watch_source->pid, child_watch_source->child_status, user_data);

  /* We never keep a child watch source around as the child is gone */
  return FALSE;
}

#ifndef G_OS_WIN32

static void
g_unix_signal_handler (int signum)
{
  unix_signal_pending[signum] = TRUE;
  any_unix_signal_pending = TRUE;

  g_wakeup_signal (glib_worker_context->wakeup);
}

#endif /* !G_OS_WIN32 */

/**
 * g_child_watch_source_new:
 * @pid: process to watch. On POSIX the pid of a child process. On
 * Windows a handle for a process (which doesn't have to be a child).
 * 
 * Creates a new child_watch source.
 *
 * The source will not initially be associated with any #GMainContext
 * and must be added to one with g_source_attach() before it will be
 * executed.
 * 
 * Note that child watch sources can only be used in conjunction with
 * <literal>g_spawn...</literal> when the %G_SPAWN_DO_NOT_REAP_CHILD
 * flag is used.
 *
 * Note that on platforms where #GPid must be explicitly closed
 * (see g_spawn_close_pid()) @pid must not be closed while the
 * source is still active. Typically, you will want to call
 * g_spawn_close_pid() in the callback function for the source.
 *
 * Note further that using g_child_watch_source_new() is not 
 * compatible with calling <literal>waitpid(-1)</literal> in 
 * the application. Calling waitpid() for individual pids will
 * still work fine. 
 * 
 * Return value: the newly-created child watch source
 *
 * Since: 2.4
 **/
GSource *
g_child_watch_source_new (GPid pid)
{
  GSource *source = g_source_new (&g_child_watch_funcs, sizeof (GChildWatchSource));
  GChildWatchSource *child_watch_source = (GChildWatchSource *)source;

  child_watch_source->pid = pid;

#ifdef G_OS_WIN32
  child_watch_source->poll.fd = (gintptr) pid;
  child_watch_source->poll.events = G_IO_IN;

  g_source_add_poll (source, &child_watch_source->poll);
#else /* G_OS_WIN32 */
  G_LOCK (unix_signal_lock);
  ensure_unix_signal_handler_installed_unlocked (SIGCHLD);
  unix_child_watches = g_slist_prepend (unix_child_watches, child_watch_source);
  if (waitpid (pid, &child_watch_source->child_status, WNOHANG) > 0)
    child_watch_source->child_exited = TRUE;
  G_UNLOCK (unix_signal_lock);
#endif /* G_OS_WIN32 */

  return source;
}

/**
 * g_child_watch_add_full:
 * @priority: the priority of the idle source. Typically this will be in the
 *            range between #G_PRIORITY_DEFAULT_IDLE and #G_PRIORITY_HIGH_IDLE.
 * @pid:      process to watch. On POSIX the pid of a child process. On
 * Windows a handle for a process (which doesn't have to be a child).
 * @function: function to call
 * @data:     data to pass to @function
 * @notify:   function to call when the idle is removed, or %NULL
 * 
 * Sets a function to be called when the child indicated by @pid 
 * exits, at the priority @priority.
 *
 * If you obtain @pid from g_spawn_async() or g_spawn_async_with_pipes() 
 * you will need to pass #G_SPAWN_DO_NOT_REAP_CHILD as flag to 
 * the spawn function for the child watching to work.
 * 
 * Note that on platforms where #GPid must be explicitly closed
 * (see g_spawn_close_pid()) @pid must not be closed while the
 * source is still active. Typically, you will want to call
 * g_spawn_close_pid() in the callback function for the source.
 * 
 * GLib supports only a single callback per process id.
 *
 * This internally creates a main loop source using 
 * g_child_watch_source_new() and attaches it to the main loop context 
 * using g_source_attach(). You can do these steps manually if you 
 * need greater control.
 *
 * Return value: the ID (greater than 0) of the event source.
 *
 * Rename to: g_child_watch_add
 * Since: 2.4
 **/
guint
g_child_watch_add_full (gint            priority,
                        GPid            pid,
                        GChildWatchFunc function,
                        gpointer        data,
                        GDestroyNotify  notify)
{
  GSource *source;
  guint id;
  
  g_return_val_if_fail (function != NULL, 0);

  source = g_child_watch_source_new (pid);

  if (priority != G_PRIORITY_DEFAULT)
    g_source_set_priority (source, priority);

  g_source_set_callback (source, (GSourceFunc) function, data, notify);
  id = g_source_attach (source, NULL);
  g_source_unref (source);

  return id;
}

/**
 * g_child_watch_add:
 * @pid:      process id to watch. On POSIX the pid of a child process. On
 * Windows a handle for a process (which doesn't have to be a child).
 * @function: function to call
 * @data:     data to pass to @function
 * 
 * Sets a function to be called when the child indicated by @pid 
 * exits, at a default priority, #G_PRIORITY_DEFAULT.
 * 
 * If you obtain @pid from g_spawn_async() or g_spawn_async_with_pipes() 
 * you will need to pass #G_SPAWN_DO_NOT_REAP_CHILD as flag to 
 * the spawn function for the child watching to work.
 * 
 * Note that on platforms where #GPid must be explicitly closed
 * (see g_spawn_close_pid()) @pid must not be closed while the
 * source is still active. Typically, you will want to call
 * g_spawn_close_pid() in the callback function for the source.
 *
 * GLib supports only a single callback per process id.
 *
 * This internally creates a main loop source using 
 * g_child_watch_source_new() and attaches it to the main loop context 
 * using g_source_attach(). You can do these steps manually if you 
 * need greater control.
 *
 * Return value: the ID (greater than 0) of the event source.
 *
 * Since: 2.4
 **/
guint 
g_child_watch_add (GPid            pid,
                   GChildWatchFunc function,
                   gpointer        data)
{
  return g_child_watch_add_full (G_PRIORITY_DEFAULT, pid, function, data, NULL);
}


/* Idle functions */

static gboolean 
g_idle_prepare  (GSource  *source,
                 gint     *timeout)
{
  *timeout = 0;

  return TRUE;
}

static gboolean 
g_idle_check    (GSource  *source)
{
  return TRUE;
}

static gboolean
g_idle_dispatch (GSource    *source, 
                 GSourceFunc callback,
                 gpointer    user_data)
{
  if (!callback)
    {
      g_warning ("Idle source dispatched without callback\n"
                 "You must call g_source_set_callback().");
      return FALSE;
    }
  
  return callback (user_data);
}

/**
 * g_idle_source_new:
 * 
 * Creates a new idle source.
 *
 * The source will not initially be associated with any #GMainContext
 * and must be added to one with g_source_attach() before it will be
 * executed. Note that the default priority for idle sources is
 * %G_PRIORITY_DEFAULT_IDLE, as compared to other sources which
 * have a default priority of %G_PRIORITY_DEFAULT.
 * 
 * Return value: the newly-created idle source
 **/
GSource *
g_idle_source_new (void)
{
  GSource *source;

  source = g_source_new (&g_idle_funcs, sizeof (GSource));
  g_source_set_priority (source, G_PRIORITY_DEFAULT_IDLE);

  return source;
}

/**
 * g_idle_add_full:
 * @priority: the priority of the idle source. Typically this will be in the
 *            range between #G_PRIORITY_DEFAULT_IDLE and #G_PRIORITY_HIGH_IDLE.
 * @function: function to call
 * @data:     data to pass to @function
 * @notify:   function to call when the idle is removed, or %NULL
 * 
 * Adds a function to be called whenever there are no higher priority
 * events pending.  If the function returns %FALSE it is automatically
 * removed from the list of event sources and will not be called again.
 * 
 * This internally creates a main loop source using g_idle_source_new()
 * and attaches it to the main loop context using g_source_attach(). 
 * You can do these steps manually if you need greater control.
 * 
 * Return value: the ID (greater than 0) of the event source.
 * Rename to: g_idle_add
 **/
guint 
g_idle_add_full (gint           priority,
                 GSourceFunc    function,
                 gpointer       data,
                 GDestroyNotify notify)
{
  GSource *source;
  guint id;
  
  g_return_val_if_fail (function != NULL, 0);

  source = g_idle_source_new ();

  if (priority != G_PRIORITY_DEFAULT_IDLE)
    g_source_set_priority (source, priority);

  g_source_set_callback (source, function, data, notify);
  id = g_source_attach (source, NULL);
  g_source_unref (source);

  return id;
}

/**
 * g_idle_add:
 * @function: function to call 
 * @data: data to pass to @function.
 * 
 * Adds a function to be called whenever there are no higher priority
 * events pending to the default main loop. The function is given the
 * default idle priority, #G_PRIORITY_DEFAULT_IDLE.  If the function
 * returns %FALSE it is automatically removed from the list of event
 * sources and will not be called again.
 * 
 * This internally creates a main loop source using g_idle_source_new()
 * and attaches it to the main loop context using g_source_attach(). 
 * You can do these steps manually if you need greater control.
 * 
 * Return value: the ID (greater than 0) of the event source.
 **/
guint 
g_idle_add (GSourceFunc    function,
            gpointer       data)
{
  return g_idle_add_full (G_PRIORITY_DEFAULT_IDLE, function, data, NULL);
}

/**
 * g_idle_remove_by_data:
 * @data: the data for the idle source's callback.
 * 
 * Removes the idle function with the given data.
 * 
 * Return value: %TRUE if an idle source was found and removed.
 **/
gboolean
g_idle_remove_by_data (gpointer data)
{
  return g_source_remove_by_funcs_user_data (&g_idle_funcs, data);
}

/**
 * g_main_context_invoke:
 * @context: (allow-none): a #GMainContext, or %NULL
 * @function: function to call
 * @data: data to pass to @function
 *
 * Invokes a function in such a way that @context is owned during the
 * invocation of @function.
 *
 * If @context is %NULL then the global default main context — as
 * returned by g_main_context_default() — is used.
 *
 * If @context is owned by the current thread, @function is called
 * directly.  Otherwise, if @context is the thread-default main context
 * of the current thread and g_main_context_acquire() succeeds, then
 * @function is called and g_main_context_release() is called
 * afterwards.
 *
 * In any other case, an idle source is created to call @function and
 * that source is attached to @context (presumably to be run in another
 * thread).  The idle source is attached with #G_PRIORITY_DEFAULT
 * priority.  If you want a different priority, use
 * g_main_context_invoke_full().
 *
 * Note that, as with normal idle functions, @function should probably
 * return %FALSE.  If it returns %TRUE, it will be continuously run in a
 * loop (and may prevent this call from returning).
 *
 * Since: 2.28
 **/
void
g_main_context_invoke (GMainContext *context,
                       GSourceFunc   function,
                       gpointer      data)
{
  g_main_context_invoke_full (context,
                              G_PRIORITY_DEFAULT,
                              function, data, NULL);
}

/**
 * g_main_context_invoke_full:
 * @context: (allow-none): a #GMainContext, or %NULL
 * @priority: the priority at which to run @function
 * @function: function to call
 * @data: data to pass to @function
 * @notify: a function to call when @data is no longer in use, or %NULL.
 *
 * Invokes a function in such a way that @context is owned during the
 * invocation of @function.
 *
 * This function is the same as g_main_context_invoke() except that it
 * lets you specify the priority incase @function ends up being
 * scheduled as an idle and also lets you give a #GDestroyNotify for @data.
 *
 * @notify should not assume that it is called from any particular
 * thread or with any particular context acquired.
 *
 * Since: 2.28
 **/
void
g_main_context_invoke_full (GMainContext   *context,
                            gint            priority,
                            GSourceFunc     function,
                            gpointer        data,
                            GDestroyNotify  notify)
{
  g_return_if_fail (function != NULL);

  if (!context)
    context = g_main_context_default ();

  if (g_main_context_is_owner (context))
    {
      while (function (data));
      if (notify != NULL)
        notify (data);
    }

  else
    {
      GMainContext *thread_default;

      thread_default = g_main_context_get_thread_default ();

      if (!thread_default)
        thread_default = g_main_context_default ();

      if (thread_default == context && g_main_context_acquire (context))
        {
          while (function (data));

          g_main_context_release (context);

          if (notify != NULL)
            notify (data);
        }
      else
        {
          GSource *source;

          source = g_idle_source_new ();
          g_source_set_priority (source, priority);
          g_source_set_callback (source, function, data, notify);
          g_source_attach (source, context);
          g_source_unref (source);
        }
    }
}

static gpointer
glib_worker_main (gpointer data)
{
  while (TRUE)
    {
      g_main_context_iteration (glib_worker_context, TRUE);

#ifdef G_OS_UNIX
      if (any_unix_signal_pending)
        dispatch_unix_signals ();
#endif
    }

  return NULL; /* worst GCC warning message ever... */
}

GMainContext *
g_get_worker_context (void)
{
  static gsize initialised;

  if (g_once_init_enter (&initialised))
    {
      /* mask all signals in the worker thread */
#ifdef G_OS_UNIX
      sigset_t prev_mask;
      sigset_t all;

      sigfillset (&all);
      pthread_sigmask (SIG_SETMASK, &all, &prev_mask);
#endif
      glib_worker_context = g_main_context_new ();
      g_thread_new ("gmain", glib_worker_main, NULL);
#ifdef G_OS_UNIX
      pthread_sigmask (SIG_SETMASK, &prev_mask, NULL);
#endif
      g_once_init_leave (&initialised, TRUE);
    }

  return glib_worker_context;
}