gio/gmemoryoutputstream.c

   1 /* GIO - GLib Input, Output and Streaming Library
   2  *
   3  * Copyright (C) 2006-2007 Red Hat, Inc.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General
  16  * Public License along with this library; if not, write to the
  17  * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  18  * Boston, MA 02111-1307, USA.
  19  *
  20  * Authors:
  21  *   Christian Kellner <gicmo@gnome.org>
  22  *   Krzysztof Kosiński <tweenk.pl@gmail.com>
  23  */
  24
  25 #include "config.h"
  26 #include "gmemoryoutputstream.h"
  27 #include "goutputstream.h"
  28 #include "gpollableoutputstream.h"
  29 #include "gseekable.h"
  30 #include "gtask.h"
  31 #include "gioerror.h"
  32 #include "string.h"
  33 #include "glibintl.h"
  34
  35
  36 /**
  37  * SECTION:gmemoryoutputstream
  38  * @short_description: Streaming output operations on memory chunks
  39  * @include: gio/gio.h
  40  * @see_also: #GMemoryInputStream
  41  *
  42  * #GMemoryOutputStream is a class for using arbitrary
  43  * memory chunks as output for GIO streaming output operations.
  44  *
  45  * As of GLib 2.34, #GMemoryOutputStream trivially implements
  46  * #GPollableOutputStream: it always polls as ready.
  47  */
  48
  49 #define MIN_ARRAY_SIZE  16
  50
  51 enum {
  52   PROP_0,
  53   PROP_DATA,
  54   PROP_SIZE,
  55   PROP_DATA_SIZE,
  56   PROP_REALLOC_FUNCTION,
  57   PROP_DESTROY_FUNCTION
  58 };
  59
  60 struct _GMemoryOutputStreamPrivate
  61 {
  62   gpointer       data; /* Write buffer */
  63   gsize          len; /* Current length of the data buffer. Can change with resizing. */
  64   gsize          valid_len; /* The part of data that has been written to */
  65   gsize          pos; /* Current position in the stream. Distinct from valid_len,
  66                          because the stream is seekable. */
  67
  68   GReallocFunc   realloc_fn;
  69   GDestroyNotify destroy;
  70 };
  71
  72 static void     g_memory_output_stream_set_property (GObject      *object,
  73                                                      guint         prop_id,
  74                                                      const GValue *value,
  75                                                      GParamSpec   *pspec);
  76 static void     g_memory_output_stream_get_property (GObject      *object,
  77                                                      guint         prop_id,
  78                                                      GValue       *value,
  79                                                      GParamSpec   *pspec);
  80 static void     g_memory_output_stream_finalize     (GObject      *object);
  81
  82 static gssize   g_memory_output_stream_write       (GOutputStream *stream,
  83                                                     const void    *buffer,
  84                                                     gsize          count,
  85                                                     GCancellable  *cancellable,
  86                                                     GError       **error);
  87
  88 static gboolean g_memory_output_stream_close       (GOutputStream  *stream,
  89                                                     GCancellable   *cancellable,
  90                                                     GError        **error);
  91
  92 static void     g_memory_output_stream_close_async  (GOutputStream        *stream,
  93                                                      int                   io_priority,
  94                                                      GCancellable         *cancellable,
  95                                                      GAsyncReadyCallback   callback,
  96                                                      gpointer              data);
  97 static gboolean g_memory_output_stream_close_finish (GOutputStream        *stream,
  98                                                      GAsyncResult         *result,
  99                                                      GError              **error);
 100
 101 static void     g_memory_output_stream_seekable_iface_init (GSeekableIface  *iface);
 102 static goffset  g_memory_output_stream_tell                (GSeekable       *seekable);
 103 static gboolean g_memory_output_stream_can_seek            (GSeekable       *seekable);
 104 static gboolean g_memory_output_stream_seek                (GSeekable       *seekable,
 105                                                            goffset          offset,
 106                                                            GSeekType        type,
 107                                                            GCancellable    *cancellable,
 108                                                            GError         **error);
 109 static gboolean g_memory_output_stream_can_truncate        (GSeekable       *seekable);
 110 static gboolean g_memory_output_stream_truncate            (GSeekable       *seekable,
 111                                                            goffset          offset,
 112                                                            GCancellable    *cancellable,
 113                                                            GError         **error);
 114
 115 static gboolean g_memory_output_stream_is_writable       (GPollableOutputStream *stream);
 116 static GSource *g_memory_output_stream_create_source     (GPollableOutputStream *stream,
 117                                                           GCancellable          *cancellable);
 118
 119 static void g_memory_output_stream_pollable_iface_init (GPollableOutputStreamInterface *iface);
 120
 121 G_DEFINE_TYPE_WITH_CODE (GMemoryOutputStream, g_memory_output_stream, G_TYPE_OUTPUT_STREAM,
 122                          G_ADD_PRIVATE (GMemoryOutputStream)
 123                          G_IMPLEMENT_INTERFACE (G_TYPE_SEEKABLE,
 124                                                 g_memory_output_stream_seekable_iface_init);
 125                          G_IMPLEMENT_INTERFACE (G_TYPE_POLLABLE_OUTPUT_STREAM,
 126                                                 g_memory_output_stream_pollable_iface_init))
 127
 128
 129 static void
 130 g_memory_output_stream_class_init (GMemoryOutputStreamClass *klass)
 131 {
 132   GOutputStreamClass *ostream_class;
 133   GObjectClass *gobject_class;
 134
 135   gobject_class = G_OBJECT_CLASS (klass);
 136   gobject_class->set_property = g_memory_output_stream_set_property;
 137   gobject_class->get_property = g_memory_output_stream_get_property;
 138   gobject_class->finalize     = g_memory_output_stream_finalize;
 139
 140   ostream_class = G_OUTPUT_STREAM_CLASS (klass);
 141
 142   ostream_class->write_fn = g_memory_output_stream_write;
 143   ostream_class->close_fn = g_memory_output_stream_close;
 144   ostream_class->close_async  = g_memory_output_stream_close_async;
 145   ostream_class->close_finish = g_memory_output_stream_close_finish;
 146
 147   /**
 148    * GMemoryOutputStream:data:
 149    *
 150    * Pointer to buffer where data will be written.
 151    *
 152    * Since: 2.24
 153    **/
 154   g_object_class_install_property (gobject_class,
 155                                    PROP_DATA,
 156                                    g_param_spec_pointer ("data",
 157                                                          P_("Data Buffer"),
 158                                                          P_("Pointer to buffer where data will be written."),
 159                                                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 160                                                          G_PARAM_STATIC_STRINGS));
 161
 162   /**
 163    * GMemoryOutputStream:size:
 164    *
 165    * Current size of the data buffer.
 166    *
 167    * Since: 2.24
 168    **/
 169   g_object_class_install_property (gobject_class,
 170                                    PROP_SIZE,
 171                                    g_param_spec_ulong ("size",
 172                                                        P_("Data Buffer Size"),
 173                                                        P_("Current size of the data buffer."),
 174                                                        0, G_MAXULONG, 0,
 175                                                        G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 176                                                        G_PARAM_STATIC_STRINGS));
 177
 178   /**
 179    * GMemoryOutputStream:data-size:
 180    *
 181    * Size of data written to the buffer.
 182    *
 183    * Since: 2.24
 184    **/
 185   g_object_class_install_property (gobject_class,
 186                                    PROP_DATA_SIZE,
 187                                    g_param_spec_ulong ("data-size",
 188                                                        P_("Data Size"),
 189                                                        P_("Size of data written to the buffer."),
 190                                                        0, G_MAXULONG, 0,
 191                                                        G_PARAM_READABLE |
 192                                                        G_PARAM_STATIC_STRINGS));
 193
 194   /**
 195    * GMemoryOutputStream:realloc-function: (skip)
 196    *
 197    * Function with realloc semantics called to enlarge the buffer.
 198    *
 199    * Since: 2.24
 200    **/
 201   g_object_class_install_property (gobject_class,
 202                                    PROP_REALLOC_FUNCTION,
 203                                    g_param_spec_pointer ("realloc-function",
 204                                                          P_("Memory Reallocation Function"),
 205                                                          P_("Function with realloc semantics called to enlarge the buffer."),
 206                                                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 207                                                          G_PARAM_STATIC_STRINGS));
 208
 209   /**
 210    * GMemoryOutputStream:destroy-function: (skip)
 211    *
 212    * Function called with the buffer as argument when the stream is destroyed.
 213    *
 214    * Since: 2.24
 215    **/
 216   g_object_class_install_property (gobject_class,
 217                                    PROP_DESTROY_FUNCTION,
 218                                    g_param_spec_pointer ("destroy-function",
 219                                                          P_("Destroy Notification Function"),
 220                                                          P_("Function called with the buffer as argument when the stream is destroyed."),
 221                                                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 222                                                          G_PARAM_STATIC_STRINGS));
 223 }
 224
 225 static void
 226 g_memory_output_stream_pollable_iface_init (GPollableOutputStreamInterface *iface)
 227 {
 228   iface->is_writable = g_memory_output_stream_is_writable;
 229   iface->create_source = g_memory_output_stream_create_source;
 230 }
 231
 232 static void
 233 g_memory_output_stream_set_property (GObject      *object,
 234                                      guint         prop_id,
 235                                      const GValue *value,
 236                                      GParamSpec   *pspec)
 237 {
 238   GMemoryOutputStream        *stream;
 239   GMemoryOutputStreamPrivate *priv;
 240
 241   stream = G_MEMORY_OUTPUT_STREAM (object);
 242   priv = stream->priv;
 243
 244   switch (prop_id)
 245     {
 246     case PROP_DATA:
 247       priv->data = g_value_get_pointer (value);
 248       break;
 249     case PROP_SIZE:
 250       priv->len = g_value_get_ulong (value);
 251       break;
 252     case PROP_REALLOC_FUNCTION:
 253       priv->realloc_fn = g_value_get_pointer (value);
 254       break;
 255     case PROP_DESTROY_FUNCTION:
 256       priv->destroy = g_value_get_pointer (value);
 257       break;
 258     default:
 259       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
 260       break;
 261     }
 262 }
 263
 264 static void
 265 g_memory_output_stream_get_property (GObject      *object,
 266                                      guint         prop_id,
 267                                      GValue       *value,
 268                                      GParamSpec   *pspec)
 269 {
 270   GMemoryOutputStream        *stream;
 271   GMemoryOutputStreamPrivate *priv;
 272
 273   stream = G_MEMORY_OUTPUT_STREAM (object);
 274   priv = stream->priv;
 275
 276   switch (prop_id)
 277     {
 278     case PROP_DATA:
 279       g_value_set_pointer (value, priv->data);
 280       break;
 281     case PROP_SIZE:
 282       g_value_set_ulong (value, priv->len);
 283       break;
 284     case PROP_DATA_SIZE:
 285       g_value_set_ulong (value, priv->valid_len);
 286       break;
 287     case PROP_REALLOC_FUNCTION:
 288       g_value_set_pointer (value, priv->realloc_fn);
 289       break;
 290     case PROP_DESTROY_FUNCTION:
 291       g_value_set_pointer (value, priv->destroy);
 292       break;
 293     default:
 294       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
 295       break;
 296     }
 297 }
 298
 299 static void
 300 g_memory_output_stream_finalize (GObject *object)
 301 {
 302   GMemoryOutputStream        *stream;
 303   GMemoryOutputStreamPrivate *priv;
 304
 305   stream = G_MEMORY_OUTPUT_STREAM (object);
 306   priv = stream->priv;
 307
 308   if (priv->destroy)
 309     priv->destroy (priv->data);
 310
 311   G_OBJECT_CLASS (g_memory_output_stream_parent_class)->finalize (object);
 312 }
 313
 314 static void
 315 g_memory_output_stream_seekable_iface_init (GSeekableIface *iface)
 316 {
 317   iface->tell         = g_memory_output_stream_tell;
 318   iface->can_seek     = g_memory_output_stream_can_seek;
 319   iface->seek         = g_memory_output_stream_seek;
 320   iface->can_truncate = g_memory_output_stream_can_truncate;
 321   iface->truncate_fn  = g_memory_output_stream_truncate;
 322 }
 323
 324
 325 static void
 326 g_memory_output_stream_init (GMemoryOutputStream *stream)
 327 {
 328   stream->priv = g_memory_output_stream_get_instance_private (stream);
 329   stream->priv->pos = 0;
 330   stream->priv->valid_len = 0;
 331 }
 332
 333 /**
 334  * g_memory_output_stream_new: (skip)
 335  * @data: (allow-none): pointer to a chunk of memory to use, or %NULL
 336  * @size: the size of @data
 337  * @realloc_function: (allow-none): a function with realloc() semantics (like g_realloc())
 338  *     to be called when @data needs to be grown, or %NULL
 339  * @destroy_function: (allow-none): a function to be called on @data when the stream is
 340  *     finalized, or %NULL
 341  *
 342  * Creates a new #GMemoryOutputStream.
 343  *
 344  * In most cases this is not the function you want.  See
 345  * g_memory_output_stream_new_resizable() instead.
 346  *
 347  * If @data is non-%NULL, the stream will use that for its internal storage.
 348  *
 349  * If @realloc_fn is non-%NULL, it will be used for resizing the internal
 350  * storage when necessary and the stream will be considered resizable.
 351  * In that case, the stream will start out being (conceptually) empty.
 352  * @size is used only as a hint for how big @data is.  Specifically,
 353  * seeking to the end of a newly-created stream will seek to zero, not
 354  * @size.  Seeking past the end of the stream and then writing will
 355  * introduce a zero-filled gap.
 356  *
 357  * If @realloc_fn is %NULL then the stream is fixed-sized.  Seeking to
 358  * the end will seek to @size exactly.  Writing past the end will give
 359  * an 'out of space' error.  Attempting to seek past the end will fail.
 360  * Unlike the resizable case, seeking to an offset within the stream and
 361  * writing will preserve the bytes passed in as @data before that point
 362  * and will return them as part of g_memory_output_stream_steal_data().
 363  * If you intend to seek you should probably therefore ensure that @data
 364  * is properly initialised.
 365  *
 366  * It is probably only meaningful to provide @data and @size in the case
 367  * that you want a fixed-sized stream.  Put another way: if @realloc_fn
 368  * is non-%NULL then it makes most sense to give @data as %NULL and
 369  * @size as 0 (allowing #GMemoryOutputStream to do the initial
 370  * allocation for itself).
 371  *
 372  * |[
 373  * /&ast; a stream that can grow &ast;/
 374  * stream = g_memory_output_stream_new (NULL, 0, realloc, free);
 375  *
 376  * /&ast; another stream that can grow &ast;/
 377  * stream2 = g_memory_output_stream_new (NULL, 0, g_realloc, g_free);
 378  *
 379  * /&ast; a fixed-size stream &ast;/
 380  * data = malloc (200);
 381  * stream3 = g_memory_output_stream_new (data, 200, NULL, free);
 382  * ]|
 383  *
 384  * Return value: A newly created #GMemoryOutputStream object.
 385  **/
 386 GOutputStream *
 387 g_memory_output_stream_new (gpointer       data,
 388                             gsize          size,
 389                             GReallocFunc   realloc_function,
 390                             GDestroyNotify destroy_function)
 391 {
 392   GOutputStream *stream;
 393
 394   stream = g_object_new (G_TYPE_MEMORY_OUTPUT_STREAM,
 395                          "data", data,
 396                          "size", size,
 397                          "realloc-function", realloc_function,
 398                          "destroy-function", destroy_function,
 399                          NULL);
 400
 401   return stream;
 402 }
 403
 404 /**
 405  * g_memory_output_stream_new_resizable:
 406  *
 407  * Creates a new #GMemoryOutputStream, using g_realloc() and g_free()
 408  * for memory allocation.
 409  *
 410  * Since: 2.36
 411  */
 412 GOutputStream *
 413 g_memory_output_stream_new_resizable (void)
 414 {
 415   return g_memory_output_stream_new (NULL, 0, g_realloc, g_free);
 416 }
 417
 418 /**
 419  * g_memory_output_stream_get_data:
 420  * @ostream: a #GMemoryOutputStream
 421  *
 422  * Gets any loaded data from the @ostream.
 423  *
 424  * Note that the returned pointer may become invalid on the next
 425  * write or truncate operation on the stream.
 426  *
 427  * Returns: (transfer none): pointer to the stream's data
 428  **/
 429 gpointer
 430 g_memory_output_stream_get_data (GMemoryOutputStream *ostream)
 431 {
 432   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
 433
 434   return ostream->priv->data;
 435 }
 436
 437 /**
 438  * g_memory_output_stream_get_size:
 439  * @ostream: a #GMemoryOutputStream
 440  *
 441  * Gets the size of the currently allocated data area (available from
 442  * g_memory_output_stream_get_data()).
 443  *
 444  * You probably don't want to use this function on resizable streams.
 445  * See g_memory_output_stream_get_data_size() instead.  For resizable
 446  * streams the size returned by this function is an implementation
 447  * detail and may be change at any time in response to operations on the
 448  * stream.
 449  *
 450  * If the stream is fixed-sized (ie: no realloc was passed to
 451  * g_memory_output_stream_new()) then this is the maximum size of the
 452  * stream and further writes will return %G_IO_ERROR_NO_SPACE.
 453  *
 454  * In any case, if you want the number of bytes currently written to the
 455  * stream, use g_memory_output_stream_get_data_size().
 456  *
 457  * Returns: the number of bytes allocated for the data buffer
 458  */
 459 gsize
 460 g_memory_output_stream_get_size (GMemoryOutputStream *ostream)
 461 {
 462   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
 463
 464   return ostream->priv->len;
 465 }
 466
 467 /**
 468  * g_memory_output_stream_get_data_size:
 469  * @ostream: a #GMemoryOutputStream
 470  *
 471  * Returns the number of bytes from the start up to including the last
 472  * byte written in the stream that has not been truncated away.
 473  *
 474  * Returns: the number of bytes written to the stream
 475  *
 476  * Since: 2.18
 477  */
 478 gsize
 479 g_memory_output_stream_get_data_size (GMemoryOutputStream *ostream)
 480 {
 481   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
 482
 483   return ostream->priv->valid_len;
 484 }
 485
 486 /**
 487  * g_memory_output_stream_steal_data:
 488  * @ostream: a #GMemoryOutputStream
 489  *
 490  * Gets any loaded data from the @ostream. Ownership of the data
 491  * is transferred to the caller; when no longer needed it must be
 492  * freed using the free function set in @ostream's
 493  * #GMemoryOutputStream:destroy-function property.
 494  *
 495  * @ostream must be closed before calling this function.
 496  *
 497  * Returns: (transfer full): the stream's data
 498  *
 499  * Since: 2.26
 500  **/
 501 gpointer
 502 g_memory_output_stream_steal_data (GMemoryOutputStream *ostream)
 503 {
 504   gpointer data;
 505
 506   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
 507   g_return_val_if_fail (g_output_stream_is_closed (G_OUTPUT_STREAM (ostream)), NULL);
 508
 509   data = ostream->priv->data;
 510   ostream->priv->data = NULL;
 511
 512   return data;
 513 }
 514
 515 /**
 516  * g_memory_output_stream_steal_as_bytes:
 517  * @ostream: a #GMemoryOutputStream
 518  *
 519  * Returns data from the @ostream as a #GBytes. @ostream must be
 520  * closed before calling this function.
 521  *
 522  * Returns: (transfer full): the stream's data
 523  *
 524  * Since: 2.34
 525  **/
 526 GBytes *
 527 g_memory_output_stream_steal_as_bytes (GMemoryOutputStream *ostream)
 528 {
 529   GBytes *result;
 530
 531   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
 532   g_return_val_if_fail (g_output_stream_is_closed (G_OUTPUT_STREAM (ostream)), NULL);
 533
 534   result = g_bytes_new_with_free_func (ostream->priv->data,
 535                                        ostream->priv->valid_len,
 536                                        ostream->priv->destroy,
 537                                        ostream->priv->data);
 538   ostream->priv->data = NULL;
 539
 540   return result;
 541 }
 542
 543 static gboolean
 544 array_resize (GMemoryOutputStream  *ostream,
 545               gsize                 size,
 546               gboolean              allow_partial,
 547               GError              **error)
 548 {
 549   GMemoryOutputStreamPrivate *priv;
 550   gpointer data;
 551   gsize len;
 552
 553   priv = ostream->priv;
 554
 555   if (priv->len == size)
 556     return TRUE;
 557
 558   if (!priv->realloc_fn)
 559     {
 560       if (allow_partial &&
 561           priv->pos < priv->len)
 562         return TRUE; /* Short write */
 563
 564       g_set_error_literal (error,
 565                            G_IO_ERROR,
 566                            G_IO_ERROR_NO_SPACE,
 567                            _("Memory output stream not resizable"));
 568       return FALSE;
 569     }
 570
 571   len = priv->len;
 572   data = priv->realloc_fn (priv->data, size);
 573
 574   if (size > 0 && !data)
 575     {
 576       if (allow_partial &&
 577           priv->pos < priv->len)
 578         return TRUE; /* Short write */
 579
 580       g_set_error_literal (error,
 581                            G_IO_ERROR,
 582                            G_IO_ERROR_NO_SPACE,
 583                            _("Failed to resize memory output stream"));
 584       return FALSE;
 585     }
 586
 587   if (size > len)
 588     memset ((guint8 *)data + len, 0, size - len);
 589
 590   priv->data = data;
 591   priv->len = size;
 592
 593   if (priv->len < priv->valid_len)
 594     priv->valid_len = priv->len;
 595
 596   return TRUE;
 597 }
 598
 599 static gint
 600 g_nearest_pow (gint num)
 601 {
 602   gint n = 1;
 603
 604   while (n < num)
 605     n <<= 1;
 606
 607   return n;
 608 }
 609
 610 static gssize
 611 g_memory_output_stream_write (GOutputStream  *stream,
 612                               const void     *buffer,
 613                               gsize           count,
 614                               GCancellable   *cancellable,
 615                               GError        **error)
 616 {
 617   GMemoryOutputStream        *ostream;
 618   GMemoryOutputStreamPrivate *priv;
 619   guint8   *dest;
 620   gsize new_size;
 621
 622   ostream = G_MEMORY_OUTPUT_STREAM (stream);
 623   priv = ostream->priv;
 624
 625   if (count == 0)
 626     return 0;
 627
 628   /* Check for address space overflow, but only if the buffer is resizable.
 629      Otherwise we just do a short write and don't worry. */
 630   if (priv->realloc_fn && priv->pos + count < priv->pos)
 631     goto overflow;
 632
 633   if (priv->pos + count > priv->len)
 634     {
 635       /* At least enough to fit the write, rounded up for greater than
 636        * linear growth.
 637        *
 638        * Assuming that we're using something like realloc(), the kernel
 639        * will overcommit memory to us, so doubling the size each time
 640        * will keep the number of realloc calls low without wasting too
 641        * much memory.
 642        */
 643       new_size = g_nearest_pow (priv->pos + count);
 644       /* Check for overflow again. We have only checked if
 645          pos + count > G_MAXSIZE, but it only catches the case of writing
 646          more than 4GiB total on a 32-bit system. There's still the problem
 647          of g_nearest_pow overflowing above 0x7fffffff, so we're
 648          effectively limited to 2GiB. */
 649       if (new_size < priv->len)
 650         goto overflow;
 651
 652       new_size = MAX (new_size, MIN_ARRAY_SIZE);
 653       if (!array_resize (ostream, new_size, TRUE, error))
 654         return -1;
 655     }
 656
 657   /* Make sure we handle short writes if the array_resize
 658      only added part of the required memory */
 659   count = MIN (count, priv->len - priv->pos);
 660
 661   dest = (guint8 *)priv->data + priv->pos;
 662   memcpy (dest, buffer, count);
 663   priv->pos += count;
 664
 665   if (priv->pos > priv->valid_len)
 666     priv->valid_len = priv->pos;
 667
 668   return count;
 669
 670  overflow:
 671   /* Overflow: buffer size would need to be bigger than G_MAXSIZE. */
 672   g_set_error_literal (error,
 673                        G_IO_ERROR,
 674                        G_IO_ERROR_NO_SPACE,
 675                        _("Amount of memory required to process the write is "
 676                          "larger than available address space"));
 677   return -1;
 678 }
 679
 680 static gboolean
 681 g_memory_output_stream_close (GOutputStream  *stream,
 682                               GCancellable   *cancellable,
 683                               GError        **error)
 684 {
 685   return TRUE;
 686 }
 687
 688 static void
 689 g_memory_output_stream_close_async (GOutputStream       *stream,
 690                                     int                  io_priority,
 691                                     GCancellable        *cancellable,
 692                                     GAsyncReadyCallback  callback,
 693                                     gpointer             data)
 694 {
 695   GTask *task;
 696
 697   task = g_task_new (stream, cancellable, callback, data);
 698
 699   /* will always return TRUE */
 700   g_memory_output_stream_close (stream, cancellable, NULL);
 701
 702   g_task_return_boolean (task, TRUE);
 703   g_object_unref (task);
 704 }
 705
 706 static gboolean
 707 g_memory_output_stream_close_finish (GOutputStream  *stream,
 708                                      GAsyncResult   *result,
 709                                      GError        **error)
 710 {
 711   g_return_val_if_fail (g_task_is_valid (result, stream), FALSE);
 712
 713   return g_task_propagate_boolean (G_TASK (result), error);
 714 }
 715
 716 static goffset
 717 g_memory_output_stream_tell (GSeekable *seekable)
 718 {
 719   GMemoryOutputStream *stream;
 720   GMemoryOutputStreamPrivate *priv;
 721
 722   stream = G_MEMORY_OUTPUT_STREAM (seekable);
 723   priv = stream->priv;
 724
 725   return priv->pos;
 726 }
 727
 728 static gboolean
 729 g_memory_output_stream_can_seek (GSeekable *seekable)
 730 {
 731   return TRUE;
 732 }
 733
 734 static gboolean
 735 g_memory_output_stream_seek (GSeekable    *seekable,
 736                              goffset        offset,
 737                              GSeekType      type,
 738                              GCancellable  *cancellable,
 739                              GError       **error)
 740 {
 741   GMemoryOutputStream        *stream;
 742   GMemoryOutputStreamPrivate *priv;
 743   goffset absolute;
 744
 745   stream = G_MEMORY_OUTPUT_STREAM (seekable);
 746   priv = stream->priv;
 747
 748   switch (type)
 749     {
 750     case G_SEEK_CUR:
 751       absolute = priv->pos + offset;
 752       break;
 753
 754     case G_SEEK_SET:
 755       absolute = offset;
 756       break;
 757
 758     case G_SEEK_END:
 759       /* For resizable streams, we consider the end to be the data
 760        * length.  For fixed-sized streams, we consider the end to be the
 761        * size of the buffer.
 762        */
 763       if (priv->realloc_fn)
 764         absolute = priv->valid_len + offset;
 765       else
 766         absolute = priv->len + offset;
 767       break;
 768
 769     default:
 770       g_set_error_literal (error,
 771                            G_IO_ERROR,
 772                            G_IO_ERROR_INVALID_ARGUMENT,
 773                            _("Invalid GSeekType supplied"));
 774
 775       return FALSE;
 776     }
 777
 778   if (absolute < 0)
 779     {
 780       g_set_error_literal (error,
 781                            G_IO_ERROR,
 782                            G_IO_ERROR_INVALID_ARGUMENT,
 783                            _("Requested seek before the beginning of the stream"));
 784       return FALSE;
 785     }
 786
 787   /* Can't seek past the end of a fixed-size stream.
 788    *
 789    * Note: seeking to the non-existent byte at the end of a fixed-sized
 790    * stream is valid (eg: a 1-byte fixed sized stream can have position
 791    * 0 or 1).  Therefore '>' is what we want.
 792    * */
 793   if (priv->realloc_fn == NULL && absolute > priv->len)
 794     {
 795       g_set_error_literal (error,
 796                            G_IO_ERROR,
 797                            G_IO_ERROR_INVALID_ARGUMENT,
 798                            _("Requested seek beyond the end of the stream"));
 799       return FALSE;
 800     }
 801
 802   priv->pos = absolute;
 803
 804   return TRUE;
 805 }
 806
 807 static gboolean
 808 g_memory_output_stream_can_truncate (GSeekable *seekable)
 809 {
 810   GMemoryOutputStream *ostream;
 811   GMemoryOutputStreamPrivate *priv;
 812
 813   ostream = G_MEMORY_OUTPUT_STREAM (seekable);
 814   priv = ostream->priv;
 815
 816   /* We do not allow truncation of fixed-sized streams */
 817   return priv->realloc_fn != NULL;
 818 }
 819
 820 static gboolean
 821 g_memory_output_stream_truncate (GSeekable     *seekable,
 822                                  goffset        offset,
 823                                  GCancellable  *cancellable,
 824                                  GError       **error)
 825 {
 826   GMemoryOutputStream *ostream = G_MEMORY_OUTPUT_STREAM (seekable);
 827
 828   if (!array_resize (ostream, offset, FALSE, error))
 829     return FALSE;
 830
 831   ostream->priv->valid_len = offset;
 832
 833   return TRUE;
 834 }
 835
 836 static gboolean
 837 g_memory_output_stream_is_writable (GPollableOutputStream *stream)
 838 {
 839   return TRUE;
 840 }
 841
 842 static GSource *
 843 g_memory_output_stream_create_source (GPollableOutputStream *stream,
 844                                       GCancellable          *cancellable)
 845 {
 846   GSource *base_source, *pollable_source;
 847
 848   base_source = g_timeout_source_new (0);
 849   pollable_source = g_pollable_source_new_full (stream, base_source, cancellable);
 850   g_source_unref (base_source);
 851
 852   return pollable_source;
 853 }