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