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 2.1 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: (nullable): pointer to a chunk of memory to use, or %NULL
 334  * @size: the size of @data
 335  * @realloc_function: (nullable): a function with realloc() semantics (like g_realloc())
 336  *     to be called when @data needs to be grown, or %NULL
 337  * @destroy_function: (nullable): 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, or %NULL if the data
 426  *    has been stolen
 427  **/
 428 gpointer
 429 g_memory_output_stream_get_data (GMemoryOutputStream *ostream)
 430 {
 431   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
 432
 433   return ostream->priv->data;
 434 }
 435
 436 /**
 437  * g_memory_output_stream_get_size:
 438  * @ostream: a #GMemoryOutputStream
 439  *
 440  * Gets the size of the currently allocated data area (available from
 441  * g_memory_output_stream_get_data()).
 442  *
 443  * You probably don't want to use this function on resizable streams.
 444  * See g_memory_output_stream_get_data_size() instead.  For resizable
 445  * streams the size returned by this function is an implementation
 446  * detail and may be change at any time in response to operations on the
 447  * stream.
 448  *
 449  * If the stream is fixed-sized (ie: no realloc was passed to
 450  * g_memory_output_stream_new()) then this is the maximum size of the
 451  * stream and further writes will return %G_IO_ERROR_NO_SPACE.
 452  *
 453  * In any case, if you want the number of bytes currently written to the
 454  * stream, use g_memory_output_stream_get_data_size().
 455  *
 456  * Returns: the number of bytes allocated for the data buffer
 457  */
 458 gsize
 459 g_memory_output_stream_get_size (GMemoryOutputStream *ostream)
 460 {
 461   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
 462
 463   return ostream->priv->len;
 464 }
 465
 466 /**
 467  * g_memory_output_stream_get_data_size:
 468  * @ostream: a #GMemoryOutputStream
 469  *
 470  * Returns the number of bytes from the start up to including the last
 471  * byte written in the stream that has not been truncated away.
 472  *
 473  * Returns: the number of bytes written to the stream
 474  *
 475  * Since: 2.18
 476  */
 477 gsize
 478 g_memory_output_stream_get_data_size (GMemoryOutputStream *ostream)
 479 {
 480   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
 481
 482   return ostream->priv->valid_len;
 483 }
 484
 485 /**
 486  * g_memory_output_stream_steal_data:
 487  * @ostream: a #GMemoryOutputStream
 488  *
 489  * Gets any loaded data from the @ostream. Ownership of the data
 490  * is transferred to the caller; when no longer needed it must be
 491  * freed using the free function set in @ostream's
 492  * #GMemoryOutputStream:destroy-function property.
 493  *
 494  * @ostream must be closed before calling this function.
 495  *
 496  * Returns: (transfer full): the stream's data, or %NULL if it has previously
 497  *    been stolen
 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 gsize
 600 g_nearest_pow (gsize num)
 601 {
 602   gsize n = 1;
 603
 604   while (n < num && n > 0)
 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 checked if
 645          pos + count > G_MAXSIZE, but now check if g_nearest_pow () has
 646          overflowed */
 647       if (new_size == 0)
 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   g_task_set_source_tag (task, g_memory_output_stream_close_async);
 697
 698   /* will always return TRUE */
 699   g_memory_output_stream_close (stream, cancellable, NULL);
 700
 701   g_task_return_boolean (task, TRUE);
 702   g_object_unref (task);
 703 }
 704
 705 static gboolean
 706 g_memory_output_stream_close_finish (GOutputStream  *stream,
 707                                      GAsyncResult   *result,
 708                                      GError        **error)
 709 {
 710   g_return_val_if_fail (g_task_is_valid (result, stream), FALSE);
 711
 712   return g_task_propagate_boolean (G_TASK (result), error);
 713 }
 714
 715 static goffset
 716 g_memory_output_stream_tell (GSeekable *seekable)
 717 {
 718   GMemoryOutputStream *stream;
 719   GMemoryOutputStreamPrivate *priv;
 720
 721   stream = G_MEMORY_OUTPUT_STREAM (seekable);
 722   priv = stream->priv;
 723
 724   return priv->pos;
 725 }
 726
 727 static gboolean
 728 g_memory_output_stream_can_seek (GSeekable *seekable)
 729 {
 730   return TRUE;
 731 }
 732
 733 static gboolean
 734 g_memory_output_stream_seek (GSeekable    *seekable,
 735                              goffset        offset,
 736                              GSeekType      type,
 737                              GCancellable  *cancellable,
 738                              GError       **error)
 739 {
 740   GMemoryOutputStream        *stream;
 741   GMemoryOutputStreamPrivate *priv;
 742   goffset absolute;
 743
 744   stream = G_MEMORY_OUTPUT_STREAM (seekable);
 745   priv = stream->priv;
 746
 747   switch (type)
 748     {
 749     case G_SEEK_CUR:
 750       absolute = priv->pos + offset;
 751       break;
 752
 753     case G_SEEK_SET:
 754       absolute = offset;
 755       break;
 756
 757     case G_SEEK_END:
 758       /* For resizable streams, we consider the end to be the data
 759        * length.  For fixed-sized streams, we consider the end to be the
 760        * size of the buffer.
 761        */
 762       if (priv->realloc_fn)
 763         absolute = priv->valid_len + offset;
 764       else
 765         absolute = priv->len + offset;
 766       break;
 767
 768     default:
 769       g_set_error_literal (error,
 770                            G_IO_ERROR,
 771                            G_IO_ERROR_INVALID_ARGUMENT,
 772                            _("Invalid GSeekType supplied"));
 773
 774       return FALSE;
 775     }
 776
 777   if (absolute < 0)
 778     {
 779       g_set_error_literal (error,
 780                            G_IO_ERROR,
 781                            G_IO_ERROR_INVALID_ARGUMENT,
 782                            _("Requested seek before the beginning of the stream"));
 783       return FALSE;
 784     }
 785
 786   /* Can't seek past the end of a fixed-size stream.
 787    *
 788    * Note: seeking to the non-existent byte at the end of a fixed-sized
 789    * stream is valid (eg: a 1-byte fixed sized stream can have position
 790    * 0 or 1).  Therefore '>' is what we want.
 791    * */
 792   if (priv->realloc_fn == NULL && (gsize) absolute > priv->len)
 793     {
 794       g_set_error_literal (error,
 795                            G_IO_ERROR,
 796                            G_IO_ERROR_INVALID_ARGUMENT,
 797                            _("Requested seek beyond the end of the stream"));
 798       return FALSE;
 799     }
 800
 801   priv->pos = absolute;
 802
 803   return TRUE;
 804 }
 805
 806 static gboolean
 807 g_memory_output_stream_can_truncate (GSeekable *seekable)
 808 {
 809   GMemoryOutputStream *ostream;
 810   GMemoryOutputStreamPrivate *priv;
 811
 812   ostream = G_MEMORY_OUTPUT_STREAM (seekable);
 813   priv = ostream->priv;
 814
 815   /* We do not allow truncation of fixed-sized streams */
 816   return priv->realloc_fn != NULL;
 817 }
 818
 819 static gboolean
 820 g_memory_output_stream_truncate (GSeekable     *seekable,
 821                                  goffset        offset,
 822                                  GCancellable  *cancellable,
 823                                  GError       **error)
 824 {
 825   GMemoryOutputStream *ostream = G_MEMORY_OUTPUT_STREAM (seekable);
 826
 827   if (!array_resize (ostream, offset, FALSE, error))
 828     return FALSE;
 829
 830   ostream->priv->valid_len = offset;
 831
 832   return TRUE;
 833 }
 834
 835 static gboolean
 836 g_memory_output_stream_is_writable (GPollableOutputStream *stream)
 837 {
 838   return TRUE;
 839 }
 840
 841 static GSource *
 842 g_memory_output_stream_create_source (GPollableOutputStream *stream,
 843                                       GCancellable          *cancellable)
 844 {
 845   GSource *base_source, *pollable_source;
 846
 847   base_source = g_timeout_source_new (0);
 848   pollable_source = g_pollable_source_new_full (stream, base_source, cancellable);
 849   g_source_unref (base_source);
 850
 851   return pollable_source;
 852 }