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 implements
  46  * #GPollableOutputStream.
  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  * If @data is non-%NULL, the stream  will use that for its internal storage.
 345  * If @realloc_fn is non-%NULL, it will be used for resizing the internal
 346  * storage when necessary. To construct a fixed-size output stream,
 347  * pass %NULL as @realloc_fn.
 348  *
 349  * |[
 350  * /&ast; a stream that can grow &ast;/
 351  * stream = g_memory_output_stream_new (NULL, 0, realloc, free);
 352  *
 353  * /&ast; another stream that can grow &ast;/
 354  * stream2 = g_memory_output_stream_new (NULL, 0, g_realloc, g_free);
 355  *
 356  * /&ast; a fixed-size stream &ast;/
 357  * data = malloc (200);
 358  * stream3 = g_memory_output_stream_new (data, 200, NULL, free);
 359  * ]|
 360  *
 361  * Return value: A newly created #GMemoryOutputStream object.
 362  **/
 363 GOutputStream *
 364 g_memory_output_stream_new (gpointer       data,
 365                             gsize          size,
 366                             GReallocFunc   realloc_function,
 367                             GDestroyNotify destroy_function)
 368 {
 369   GOutputStream *stream;
 370
 371   stream = g_object_new (G_TYPE_MEMORY_OUTPUT_STREAM,
 372                          "data", data,
 373                          "size", size,
 374                          "realloc-function", realloc_function,
 375                          "destroy-function", destroy_function,
 376                          NULL);
 377
 378   return stream;
 379 }
 380
 381 /**
 382  * g_memory_output_stream_new_resizable:
 383  *
 384  * Creates a new #GMemoryOutputStream, using g_realloc() and g_free()
 385  * for memory allocation.
 386  *
 387  * Since: 2.36
 388  */
 389 GOutputStream *
 390 g_memory_output_stream_new_resizable (void)
 391 {
 392   return g_memory_output_stream_new (NULL, 0, g_realloc, g_free);
 393 }
 394
 395 /**
 396  * g_memory_output_stream_get_data:
 397  * @ostream: a #GMemoryOutputStream
 398  *
 399  * Gets any loaded data from the @ostream.
 400  *
 401  * Note that the returned pointer may become invalid on the next
 402  * write or truncate operation on the stream.
 403  *
 404  * Returns: (transfer none): pointer to the stream's data
 405  **/
 406 gpointer
 407 g_memory_output_stream_get_data (GMemoryOutputStream *ostream)
 408 {
 409   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
 410
 411   return ostream->priv->data;
 412 }
 413
 414 /**
 415  * g_memory_output_stream_get_size:
 416  * @ostream: a #GMemoryOutputStream
 417  *
 418  * Gets the size of the currently allocated data area (available from
 419  * g_memory_output_stream_get_data()). If the stream isn't
 420  * growable (no realloc was passed to g_memory_output_stream_new()) then
 421  * this is the maximum size of the stream and further writes
 422  * will return %G_IO_ERROR_NO_SPACE.
 423  *
 424  * Note that for growable streams the returned size may become invalid on
 425  * the next write or truncate operation on the stream.
 426  *
 427  * If you want the number of bytes currently written to the stream, use
 428  * g_memory_output_stream_get_data_size().
 429  *
 430  * Returns: the number of bytes allocated for the data buffer
 431  */
 432 gsize
 433 g_memory_output_stream_get_size (GMemoryOutputStream *ostream)
 434 {
 435   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
 436
 437   return ostream->priv->len;
 438 }
 439
 440 /**
 441  * g_memory_output_stream_get_data_size:
 442  * @ostream: a #GMemoryOutputStream
 443  *
 444  * Returns the number of bytes from the start up
 445  * to including the last byte written in the stream
 446  * that has not been truncated away.
 447  *
 448  * Returns: the number of bytes written to the stream
 449  *
 450  * Since: 2.18
 451  */
 452 gsize
 453 g_memory_output_stream_get_data_size (GMemoryOutputStream *ostream)
 454 {
 455   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
 456
 457   return ostream->priv->valid_len;
 458 }
 459
 460 /**
 461  * g_memory_output_stream_steal_data:
 462  * @ostream: a #GMemoryOutputStream
 463  *
 464  * Gets any loaded data from the @ostream. Ownership of the data
 465  * is transferred to the caller; when no longer needed it must be
 466  * freed using the free function set in @ostream's
 467  * #GMemoryOutputStream:destroy-function property.
 468  *
 469  * @ostream must be closed before calling this function.
 470  *
 471  * Returns: (transfer full): the stream's data
 472  *
 473  * Since: 2.26
 474  **/
 475 gpointer
 476 g_memory_output_stream_steal_data (GMemoryOutputStream *ostream)
 477 {
 478   gpointer data;
 479
 480   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
 481   g_return_val_if_fail (g_output_stream_is_closed (G_OUTPUT_STREAM (ostream)), NULL);
 482
 483   data = ostream->priv->data;
 484   ostream->priv->data = NULL;
 485
 486   return data;
 487 }
 488
 489 /**
 490  * g_memory_output_stream_steal_as_bytes:
 491  * @ostream: a #GMemoryOutputStream
 492  *
 493  * Returns data from the @ostream as a #GBytes. @ostream must be
 494  * closed before calling this function.
 495  *
 496  * Returns: (transfer full): the stream's data
 497  *
 498  * Since: 2.34
 499  **/
 500 GBytes *
 501 g_memory_output_stream_steal_as_bytes (GMemoryOutputStream *ostream)
 502 {
 503   GBytes *result;
 504
 505   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
 506   g_return_val_if_fail (g_output_stream_is_closed (G_OUTPUT_STREAM (ostream)), NULL);
 507
 508   result = g_bytes_new_with_free_func (ostream->priv->data,
 509                                        ostream->priv->valid_len,
 510                                        ostream->priv->destroy,
 511                                        ostream->priv->data);
 512   ostream->priv->data = NULL;
 513
 514   return result;
 515 }
 516
 517 static gboolean
 518 array_resize (GMemoryOutputStream  *ostream,
 519               gsize                 size,
 520               gboolean              allow_partial,
 521               GError              **error)
 522 {
 523   GMemoryOutputStreamPrivate *priv;
 524   gpointer data;
 525   gsize len;
 526
 527   priv = ostream->priv;
 528
 529   if (priv->len == size)
 530     return TRUE;
 531
 532   if (!priv->realloc_fn)
 533     {
 534       if (allow_partial &&
 535           priv->pos < priv->len)
 536         return TRUE; /* Short write */
 537
 538       g_set_error_literal (error,
 539                            G_IO_ERROR,
 540                            G_IO_ERROR_NO_SPACE,
 541                            _("Memory output stream not resizable"));
 542       return FALSE;
 543     }
 544
 545   len = priv->len;
 546   data = priv->realloc_fn (priv->data, size);
 547
 548   if (size > 0 && !data)
 549     {
 550       if (allow_partial &&
 551           priv->pos < priv->len)
 552         return TRUE; /* Short write */
 553
 554       g_set_error_literal (error,
 555                            G_IO_ERROR,
 556                            G_IO_ERROR_NO_SPACE,
 557                            _("Failed to resize memory output stream"));
 558       return FALSE;
 559     }
 560
 561   if (size > len)
 562     memset ((guint8 *)data + len, 0, size - len);
 563
 564   priv->data = data;
 565   priv->len = size;
 566
 567   if (priv->len < priv->valid_len)
 568     priv->valid_len = priv->len;
 569
 570   return TRUE;
 571 }
 572
 573 static gint
 574 g_nearest_pow (gint num)
 575 {
 576   gint n = 1;
 577
 578   while (n < num)
 579     n <<= 1;
 580
 581   return n;
 582 }
 583
 584 static gssize
 585 g_memory_output_stream_write (GOutputStream  *stream,
 586                               const void     *buffer,
 587                               gsize           count,
 588                               GCancellable   *cancellable,
 589                               GError        **error)
 590 {
 591   GMemoryOutputStream        *ostream;
 592   GMemoryOutputStreamPrivate *priv;
 593   guint8   *dest;
 594   gsize new_size;
 595
 596   ostream = G_MEMORY_OUTPUT_STREAM (stream);
 597   priv = ostream->priv;
 598
 599   if (count == 0)
 600     return 0;
 601
 602   /* Check for address space overflow, but only if the buffer is resizable.
 603      Otherwise we just do a short write and don't worry. */
 604   if (priv->realloc_fn && priv->pos + count < priv->pos)
 605     goto overflow;
 606
 607   if (priv->pos + count > priv->len)
 608     {
 609       /* At least enought to fit the write, rounded up
 610              for greater than linear growth.
 611          TODO: This wastes a lot of memory at large stream sizes.
 612                Figure out a more rational allocation strategy. */
 613       new_size = g_nearest_pow (priv->pos + count);
 614       /* Check for overflow again. We have only checked if
 615          pos + count > G_MAXSIZE, but it only catches the case of writing
 616          more than 4GiB total on a 32-bit system. There's still the problem
 617          of g_nearest_pow overflowing above 0x7fffffff, so we're
 618          effectively limited to 2GiB. */
 619       if (new_size < priv->len)
 620         goto overflow;
 621
 622       new_size = MAX (new_size, MIN_ARRAY_SIZE);
 623       if (!array_resize (ostream, new_size, TRUE, error))
 624         return -1;
 625     }
 626
 627   /* Make sure we handle short writes if the array_resize
 628      only added part of the required memory */
 629   count = MIN (count, priv->len - priv->pos);
 630
 631   dest = (guint8 *)priv->data + priv->pos;
 632   memcpy (dest, buffer, count);
 633   priv->pos += count;
 634
 635   if (priv->pos > priv->valid_len)
 636     priv->valid_len = priv->pos;
 637
 638   return count;
 639
 640  overflow:
 641   /* Overflow: buffer size would need to be bigger than G_MAXSIZE. */
 642   g_set_error_literal (error,
 643                        G_IO_ERROR,
 644                        G_IO_ERROR_NO_SPACE,
 645                        _("Amount of memory required to process the write is "
 646                          "larger than available address space"));
 647   return -1;
 648 }
 649
 650 static gboolean
 651 g_memory_output_stream_close (GOutputStream  *stream,
 652                               GCancellable   *cancellable,
 653                               GError        **error)
 654 {
 655   return TRUE;
 656 }
 657
 658 static void
 659 g_memory_output_stream_close_async (GOutputStream       *stream,
 660                                     int                  io_priority,
 661                                     GCancellable        *cancellable,
 662                                     GAsyncReadyCallback  callback,
 663                                     gpointer             data)
 664 {
 665   GTask *task;
 666
 667   task = g_task_new (stream, cancellable, callback, data);
 668
 669   /* will always return TRUE */
 670   g_memory_output_stream_close (stream, cancellable, NULL);
 671
 672   g_task_return_boolean (task, TRUE);
 673   g_object_unref (task);
 674 }
 675
 676 static gboolean
 677 g_memory_output_stream_close_finish (GOutputStream  *stream,
 678                                      GAsyncResult   *result,
 679                                      GError        **error)
 680 {
 681   g_return_val_if_fail (g_task_is_valid (result, stream), FALSE);
 682
 683   return g_task_propagate_boolean (G_TASK (result), error);
 684 }
 685
 686 static goffset
 687 g_memory_output_stream_tell (GSeekable *seekable)
 688 {
 689   GMemoryOutputStream *stream;
 690   GMemoryOutputStreamPrivate *priv;
 691
 692   stream = G_MEMORY_OUTPUT_STREAM (seekable);
 693   priv = stream->priv;
 694
 695   return priv->pos;
 696 }
 697
 698 static gboolean
 699 g_memory_output_stream_can_seek (GSeekable *seekable)
 700 {
 701   return TRUE;
 702 }
 703
 704 static gboolean
 705 g_memory_output_stream_seek (GSeekable    *seekable,
 706                             goffset        offset,
 707                             GSeekType      type,
 708                             GCancellable  *cancellable,
 709                             GError       **error)
 710 {
 711   GMemoryOutputStream        *stream;
 712   GMemoryOutputStreamPrivate *priv;
 713   goffset absolute;
 714
 715   stream = G_MEMORY_OUTPUT_STREAM (seekable);
 716   priv = stream->priv;
 717
 718   switch (type)
 719     {
 720     case G_SEEK_CUR:
 721       absolute = priv->pos + offset;
 722       break;
 723
 724     case G_SEEK_SET:
 725       absolute = offset;
 726       break;
 727
 728     case G_SEEK_END:
 729       /* For resizable streams, we consider the end to be the data
 730        * length.  For fixed-sized streams, we consider the end to be the
 731        * size of the buffer.
 732        */
 733       if (priv->realloc_fn)
 734         absolute = priv->valid_len + offset;
 735       else
 736         absolute = priv->len + offset;
 737       break;
 738
 739     default:
 740       g_set_error_literal (error,
 741                            G_IO_ERROR,
 742                            G_IO_ERROR_INVALID_ARGUMENT,
 743                            _("Invalid GSeekType supplied"));
 744
 745       return FALSE;
 746     }
 747
 748   if (absolute < 0)
 749     {
 750       g_set_error_literal (error,
 751                            G_IO_ERROR,
 752                            G_IO_ERROR_INVALID_ARGUMENT,
 753                            _("Requested seek before the beginning of the stream"));
 754       return FALSE;
 755     }
 756
 757   /* Can't seek past the end of a fixed-size stream.
 758    *
 759    * Note: seeking to the non-existent byte at the end of a fixed-sized
 760    * stream is valid (eg: a 1-byte fixed sized stream can have position
 761    * 0 or 1).  Therefore '>' is what we want.
 762    * */
 763   if (priv->realloc_fn == NULL && absolute > priv->len)
 764     {
 765       g_set_error_literal (error,
 766                            G_IO_ERROR,
 767                            G_IO_ERROR_INVALID_ARGUMENT,
 768                            _("Requested seek beyond the end of the stream"));
 769       return FALSE;
 770     }
 771
 772   priv->pos = absolute;
 773
 774   return TRUE;
 775 }
 776
 777 static gboolean
 778 g_memory_output_stream_can_truncate (GSeekable *seekable)
 779 {
 780   GMemoryOutputStream *ostream;
 781   GMemoryOutputStreamPrivate *priv;
 782
 783   ostream = G_MEMORY_OUTPUT_STREAM (seekable);
 784   priv = ostream->priv;
 785
 786   return priv->realloc_fn != NULL;
 787 }
 788
 789 static gboolean
 790 g_memory_output_stream_truncate (GSeekable     *seekable,
 791                                  goffset        offset,
 792                                  GCancellable  *cancellable,
 793                                  GError       **error)
 794 {
 795   GMemoryOutputStream *ostream = G_MEMORY_OUTPUT_STREAM (seekable);
 796
 797   if (!array_resize (ostream, offset, FALSE, error))
 798     return FALSE;
 799
 800   return TRUE;
 801 }
 802
 803 static gboolean
 804 g_memory_output_stream_is_writable (GPollableOutputStream *stream)
 805 {
 806   return TRUE;
 807 }
 808
 809 static GSource *
 810 g_memory_output_stream_create_source (GPollableOutputStream *stream,
 811                                       GCancellable          *cancellable)
 812 {
 813   GSource *base_source, *pollable_source;
 814
 815   base_source = g_timeout_source_new (0);
 816   pollable_source = g_pollable_source_new_full (stream, base_source,
 817                                                 cancellable);
 818   g_source_unref (base_source);
 819
 820   return pollable_source;
 821 }