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 "gseekable.h"
  29 #include "gsimpleasyncresult.h"
  30 #include "gioerror.h"
  31 #include "string.h"
  32 #include "glibintl.h"
  33
  34 #include "gioalias.h"
  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  */
  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_write_async  (GOutputStream        *stream,
  91                                                      const void           *buffer,
  92                                                      gsize                 count,
  93                                                      int                   io_priority,
  94                                                      GCancellable         *cancellable,
  95                                                      GAsyncReadyCallback   callback,
  96                                                      gpointer              data);
  97 static gssize   g_memory_output_stream_write_finish (GOutputStream        *stream,
  98                                                      GAsyncResult         *result,
  99                                                      GError              **error);
 100 static void     g_memory_output_stream_close_async  (GOutputStream        *stream,
 101                                                      int                   io_priority,
 102                                                      GCancellable         *cancellable,
 103                                                      GAsyncReadyCallback   callback,
 104                                                      gpointer              data);
 105 static gboolean g_memory_output_stream_close_finish (GOutputStream        *stream,
 106                                                      GAsyncResult         *result,
 107                                                      GError              **error);
 108
 109 static void     g_memory_output_stream_seekable_iface_init (GSeekableIface  *iface);
 110 static goffset  g_memory_output_stream_tell                (GSeekable       *seekable);
 111 static gboolean g_memory_output_stream_can_seek            (GSeekable       *seekable);
 112 static gboolean g_memory_output_stream_seek                (GSeekable       *seekable,
 113                                                            goffset          offset,
 114                                                            GSeekType        type,
 115                                                            GCancellable    *cancellable,
 116                                                            GError         **error);
 117 static gboolean g_memory_output_stream_can_truncate        (GSeekable       *seekable);
 118 static gboolean g_memory_output_stream_truncate            (GSeekable       *seekable,
 119                                                            goffset          offset,
 120                                                            GCancellable    *cancellable,
 121                                                            GError         **error);
 122
 123 G_DEFINE_TYPE_WITH_CODE (GMemoryOutputStream, g_memory_output_stream, G_TYPE_OUTPUT_STREAM,
 124                          G_IMPLEMENT_INTERFACE (G_TYPE_SEEKABLE,
 125                                                 g_memory_output_stream_seekable_iface_init))
 126
 127
 128 static void
 129 g_memory_output_stream_class_init (GMemoryOutputStreamClass *klass)
 130 {
 131   GOutputStreamClass *ostream_class;
 132   GObjectClass *gobject_class;
 133
 134   g_type_class_add_private (klass, sizeof (GMemoryOutputStreamPrivate));
 135
 136   gobject_class = G_OBJECT_CLASS (klass);
 137   gobject_class->set_property = g_memory_output_stream_set_property;
 138   gobject_class->get_property = g_memory_output_stream_get_property;
 139   gobject_class->finalize     = g_memory_output_stream_finalize;
 140
 141   ostream_class = G_OUTPUT_STREAM_CLASS (klass);
 142
 143   ostream_class->write_fn = g_memory_output_stream_write;
 144   ostream_class->close_fn = g_memory_output_stream_close;
 145   ostream_class->write_async  = g_memory_output_stream_write_async;
 146   ostream_class->write_finish = g_memory_output_stream_write_finish;
 147   ostream_class->close_async  = g_memory_output_stream_close_async;
 148   ostream_class->close_finish = g_memory_output_stream_close_finish;
 149
 150   /**
 151    * GMemoryOutputStream:data:
 152    *
 153    * Pointer to buffer where data will be written.
 154    *
 155    * Since: 2.24
 156    **/
 157   g_object_class_install_property (gobject_class,
 158                                    PROP_DATA,
 159                                    g_param_spec_pointer ("data",
 160                                                          P_("Data Buffer"),
 161                                                          P_("Pointer to buffer where data will be written."),
 162                                                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 163                                                          G_PARAM_STATIC_STRINGS));
 164
 165   /**
 166    * GMemoryOutputStream:size:
 167    *
 168    * Current size of the data buffer.
 169    *
 170    * Since: 2.24
 171    **/
 172   g_object_class_install_property (gobject_class,
 173                                    PROP_SIZE,
 174                                    g_param_spec_ulong ("size",
 175                                                        P_("Data Buffer Size"),
 176                                                        P_("Current size of the data buffer."),
 177                                                        0, G_MAXULONG, 0,
 178                                                        G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 179                                                        G_PARAM_STATIC_STRINGS));
 180
 181   /**
 182    * GMemoryOutputStream:data-size:
 183    *
 184    * Size of data written to the buffer.
 185    *
 186    * Since: 2.24
 187    **/
 188   g_object_class_install_property (gobject_class,
 189                                    PROP_DATA_SIZE,
 190                                    g_param_spec_ulong ("data-size",
 191                                                        P_("Data Size"),
 192                                                        P_("Size of data written to the buffer."),
 193                                                        0, G_MAXULONG, 0,
 194                                                        G_PARAM_READABLE |
 195                                                        G_PARAM_STATIC_STRINGS));
 196
 197   /**
 198    * GMemoryOutputStream:realloc-function:
 199    *
 200    * Function with realloc semantics called to enlarge the buffer.
 201    *
 202    * Since: 2.24
 203    **/
 204   g_object_class_install_property (gobject_class,
 205                                    PROP_REALLOC_FUNCTION,
 206                                    g_param_spec_pointer ("realloc-function",
 207                                                          P_("Memory Reallocation Function"),
 208                                                          P_("Function with realloc semantics called to enlarge the buffer."),
 209                                                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 210                                                          G_PARAM_STATIC_STRINGS));
 211
 212   /**
 213    * GMemoryOutputStream:destroy-function:
 214    *
 215    * Function called with the buffer as argument when the stream is destroyed.
 216    *
 217    * Since: 2.24
 218    **/
 219   g_object_class_install_property (gobject_class,
 220                                    PROP_DESTROY_FUNCTION,
 221                                    g_param_spec_pointer ("destroy-function",
 222                                                          P_("Destroy Notification Function"),
 223                                                          P_("Function called with the buffer as argument when the stream is destroyed."),
 224                                                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 225                                                          G_PARAM_STATIC_STRINGS));
 226 }
 227
 228 static void
 229 g_memory_output_stream_set_property (GObject      *object,
 230                                      guint         prop_id,
 231                                      const GValue *value,
 232                                      GParamSpec   *pspec)
 233 {
 234   GMemoryOutputStream        *stream;
 235   GMemoryOutputStreamPrivate *priv;
 236
 237   stream = G_MEMORY_OUTPUT_STREAM (object);
 238   priv = stream->priv;
 239
 240   switch (prop_id)
 241     {
 242     case PROP_DATA:
 243       priv->data = g_value_get_pointer (value);
 244       break;
 245     case PROP_SIZE:
 246       priv->len = g_value_get_ulong (value);
 247       break;
 248     case PROP_REALLOC_FUNCTION:
 249       priv->realloc_fn = g_value_get_pointer (value);
 250       break;
 251     case PROP_DESTROY_FUNCTION:
 252       priv->destroy = g_value_get_pointer (value);
 253       break;
 254     default:
 255       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
 256       break;
 257     }
 258 }
 259
 260 static void
 261 g_memory_output_stream_get_property (GObject      *object,
 262                                      guint         prop_id,
 263                                      GValue       *value,
 264                                      GParamSpec   *pspec)
 265 {
 266   GMemoryOutputStream        *stream;
 267   GMemoryOutputStreamPrivate *priv;
 268
 269   stream = G_MEMORY_OUTPUT_STREAM (object);
 270   priv = stream->priv;
 271
 272   switch (prop_id)
 273     {
 274     case PROP_DATA:
 275       g_value_set_pointer (value, priv->data);
 276       break;
 277     case PROP_SIZE:
 278       g_value_set_ulong (value, priv->len);
 279       break;
 280     case PROP_DATA_SIZE:
 281       g_value_set_ulong (value, priv->valid_len);
 282       break;
 283     case PROP_REALLOC_FUNCTION:
 284       g_value_set_pointer (value, priv->realloc_fn);
 285       break;
 286     case PROP_DESTROY_FUNCTION:
 287       g_value_set_pointer (value, priv->destroy);
 288       break;
 289     default:
 290       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
 291       break;
 292     }
 293 }
 294
 295 static void
 296 g_memory_output_stream_finalize (GObject *object)
 297 {
 298   GMemoryOutputStream        *stream;
 299   GMemoryOutputStreamPrivate *priv;
 300
 301   stream = G_MEMORY_OUTPUT_STREAM (object);
 302   priv = stream->priv;
 303
 304   if (priv->destroy)
 305     priv->destroy (priv->data);
 306
 307   G_OBJECT_CLASS (g_memory_output_stream_parent_class)->finalize (object);
 308 }
 309
 310 static void
 311 g_memory_output_stream_seekable_iface_init (GSeekableIface *iface)
 312 {
 313   iface->tell         = g_memory_output_stream_tell;
 314   iface->can_seek     = g_memory_output_stream_can_seek;
 315   iface->seek         = g_memory_output_stream_seek;
 316   iface->can_truncate = g_memory_output_stream_can_truncate;
 317   iface->truncate_fn  = g_memory_output_stream_truncate;
 318 }
 319
 320
 321 static void
 322 g_memory_output_stream_init (GMemoryOutputStream *stream)
 323 {
 324   stream->priv = G_TYPE_INSTANCE_GET_PRIVATE (stream,
 325                                               G_TYPE_MEMORY_OUTPUT_STREAM,
 326                                               GMemoryOutputStreamPrivate);
 327   stream->priv->pos = 0;
 328   stream->priv->valid_len = 0;
 329 }
 330
 331 /**
 332  * g_memory_output_stream_new:
 333  * @data: pointer to a chunk of memory to use, or %NULL
 334  * @size: the size of @data
 335  * @realloc_function: a function with realloc() semantics (like g_realloc())
 336  *     to be called when @data needs to be grown, or %NULL
 337  * @destroy_function: a function to be called on @data when the stream is
 338  *     finalized, or %NULL
 339  *
 340  * Creates a new #GMemoryOutputStream.
 341  *
 342  * If @data is non-%NULL, the stream  will use that for its internal storage.
 343  * If @realloc_fn is non-%NULL, it will be used for resizing the internal
 344  * storage when necessary. To construct a fixed-size output stream,
 345  * pass %NULL as @realloc_fn.
 346  *
 347  * |[
 348  * /&ast; a stream that can grow &ast;/
 349  * stream = g_memory_output_stream_new (NULL, 0, realloc, free);
 350  *
 351  * /&ast; another stream that can grow &ast;/
 352  * stream2 = g_memory_output_stream_new (NULL, 0, g_realloc, g_free);
 353  *
 354  * /&ast; a fixed-size stream &ast;/
 355  * data = malloc (200);
 356  * stream3 = g_memory_output_stream_new (data, 200, NULL, free);
 357  * ]|
 358  *
 359  * Return value: A newly created #GMemoryOutputStream object.
 360  **/
 361 GOutputStream *
 362 g_memory_output_stream_new (gpointer       data,
 363                             gsize          size,
 364                             GReallocFunc   realloc_function,
 365                             GDestroyNotify destroy_function)
 366 {
 367   GOutputStream *stream;
 368
 369   stream = g_object_new (G_TYPE_MEMORY_OUTPUT_STREAM,
 370                          "data", data,
 371                          "size", size,
 372                          "realloc-function", realloc_function,
 373                          "destroy-function", destroy_function,
 374                          NULL);
 375
 376   return stream;
 377 }
 378
 379 /**
 380  * g_memory_output_stream_get_data:
 381  * @ostream: a #GMemoryOutputStream
 382  *
 383  * Gets any loaded data from the @ostream.
 384  *
 385  * Note that the returned pointer may become invalid on the next
 386  * write or truncate operation on the stream.
 387  *
 388  * Returns: pointer to the stream's data
 389  **/
 390 gpointer
 391 g_memory_output_stream_get_data (GMemoryOutputStream *ostream)
 392 {
 393   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
 394
 395   return ostream->priv->data;
 396 }
 397
 398 /**
 399  * g_memory_output_stream_get_size:
 400  * @ostream: a #GMemoryOutputStream
 401  *
 402  * Gets the size of the currently allocated data area (availible from
 403  * g_memory_output_stream_get_data()). If the stream isn't
 404  * growable (no realloc was passed to g_memory_output_stream_new()) then
 405  * this is the maximum size of the stream and further writes
 406  * will return %G_IO_ERROR_NO_SPACE.
 407  *
 408  * Note that for growable streams the returned size may become invalid on
 409  * the next write or truncate operation on the stream.
 410  *
 411  * If you want the number of bytes currently written to the stream, use
 412  * g_memory_output_stream_get_data_size().
 413  *
 414  * Returns: the number of bytes allocated for the data buffer
 415  */
 416 gsize
 417 g_memory_output_stream_get_size (GMemoryOutputStream *ostream)
 418 {
 419   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
 420
 421   return ostream->priv->len;
 422 }
 423
 424 /**
 425  * g_memory_output_stream_get_data_size:
 426  * @ostream: a #GMemoryOutputStream
 427  *
 428  * Returns the number of bytes from the start up
 429  * to including the last byte written in the stream
 430  * that has not been truncated away.
 431  *
 432  * Returns: the number of bytes written to the stream
 433  *
 434  * Since: 2.18
 435  */
 436 gsize
 437 g_memory_output_stream_get_data_size (GMemoryOutputStream *ostream)
 438 {
 439   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
 440
 441   return ostream->priv->valid_len;
 442 }
 443
 444 static gboolean
 445 array_resize (GMemoryOutputStream  *ostream,
 446               gsize                 size,
 447               gboolean              allow_partial,
 448               GError              **error)
 449 {
 450   GMemoryOutputStreamPrivate *priv;
 451   gpointer data;
 452   gsize len;
 453
 454   priv = ostream->priv;
 455
 456   if (priv->len == size)
 457     return TRUE;
 458
 459   if (!priv->realloc_fn)
 460     {
 461       if (allow_partial &&
 462           priv->pos < priv->len)
 463         return TRUE; /* Short write */
 464
 465       g_set_error_literal (error,
 466                            G_IO_ERROR,
 467                            G_IO_ERROR_NO_SPACE,
 468                            _("Memory output stream not resizable"));
 469       return FALSE;
 470     }
 471
 472   len = priv->len;
 473   data = priv->realloc_fn (priv->data, size);
 474
 475   if (size > 0 && !data)
 476     {
 477       if (allow_partial &&
 478           priv->pos < priv->len)
 479         return TRUE; /* Short write */
 480
 481       g_set_error_literal (error,
 482                            G_IO_ERROR,
 483                            G_IO_ERROR_NO_SPACE,
 484                            _("Failed to resize memory output stream"));
 485       return FALSE;
 486     }
 487
 488   if (size > len)
 489     memset ((guint8 *)data + len, 0, size - len);
 490
 491   priv->data = data;
 492   priv->len = size;
 493
 494   if (priv->len < priv->valid_len)
 495     priv->valid_len = priv->len;
 496
 497   return TRUE;
 498 }
 499
 500 static gint
 501 g_nearest_pow (gint num)
 502 {
 503   gint n = 1;
 504
 505   while (n < num)
 506     n <<= 1;
 507
 508   return n;
 509 }
 510
 511 static gssize
 512 g_memory_output_stream_write (GOutputStream  *stream,
 513                               const void     *buffer,
 514                               gsize           count,
 515                               GCancellable   *cancellable,
 516                               GError        **error)
 517 {
 518   GMemoryOutputStream        *ostream;
 519   GMemoryOutputStreamPrivate *priv;
 520   guint8   *dest;
 521   gsize new_size;
 522
 523   ostream = G_MEMORY_OUTPUT_STREAM (stream);
 524   priv = ostream->priv;
 525
 526   if (count == 0)
 527     return 0;
 528
 529   /* Check for address space overflow, but only if the buffer is resizable.
 530      Otherwise we just do a short write and don't worry. */
 531   if (priv->realloc_fn && priv->pos + count < priv->pos)
 532     goto overflow;
 533
 534   if (priv->pos + count > priv->len)
 535     {
 536       /* At least enought to fit the write, rounded up
 537              for greater than linear growth.
 538          TODO: This wastes a lot of memory at large stream sizes.
 539                Figure out a more rational allocation strategy. */
 540       new_size = g_nearest_pow (priv->pos + count);
 541       /* Check for overflow again. We have only checked if
 542          pos + count > G_MAXSIZE, but it only catches the case of writing
 543          more than 4GiB total on a 32-bit system. There's still the problem
 544          of g_nearest_pow overflowing above 0x7fffffff, so we're
 545          effectively limited to 2GiB. */
 546       if (new_size < priv->len)
 547         goto overflow;
 548
 549       new_size = MAX (new_size, MIN_ARRAY_SIZE);
 550       if (!array_resize (ostream, new_size, TRUE, error))
 551         return -1;
 552     }
 553
 554   /* Make sure we handle short writes if the array_resize
 555      only added part of the required memory */
 556   count = MIN (count, priv->len - priv->pos);
 557
 558   dest = (guint8 *)priv->data + priv->pos;
 559   memcpy (dest, buffer, count);
 560   priv->pos += count;
 561
 562   if (priv->pos > priv->valid_len)
 563     priv->valid_len = priv->pos;
 564
 565   return count;
 566
 567  overflow:
 568   /* Overflow: buffer size would need to be bigger than G_MAXSIZE. */
 569   g_set_error_literal (error,
 570                        G_IO_ERROR,
 571                        G_IO_ERROR_NO_SPACE,
 572                        _("Amount of memory required to process the write is "
 573                          "larger than available address space"));
 574   return -1;
 575 }
 576
 577 static gboolean
 578 g_memory_output_stream_close (GOutputStream  *stream,
 579                               GCancellable   *cancellable,
 580                               GError        **error)
 581 {
 582   return TRUE;
 583 }
 584
 585 static void
 586 g_memory_output_stream_write_async (GOutputStream       *stream,
 587                                     const void          *buffer,
 588                                     gsize                count,
 589                                     int                  io_priority,
 590                                     GCancellable        *cancellable,
 591                                     GAsyncReadyCallback  callback,
 592                                     gpointer             data)
 593 {
 594   GSimpleAsyncResult *simple;
 595   gssize nwritten;
 596
 597   nwritten = g_memory_output_stream_write (stream,
 598                                            buffer,
 599                                            count,
 600                                            cancellable,
 601                                            NULL);
 602
 603   simple = g_simple_async_result_new (G_OBJECT (stream),
 604                                       callback,
 605                                       data,
 606                                       g_memory_output_stream_write_async);
 607
 608   g_simple_async_result_set_op_res_gssize (simple, nwritten);
 609   g_simple_async_result_complete_in_idle (simple);
 610   g_object_unref (simple);
 611 }
 612
 613 static gssize
 614 g_memory_output_stream_write_finish (GOutputStream  *stream,
 615                                      GAsyncResult   *result,
 616                                      GError        **error)
 617 {
 618   GSimpleAsyncResult *simple;
 619   gssize nwritten;
 620
 621   simple = G_SIMPLE_ASYNC_RESULT (result);
 622
 623   g_warn_if_fail (g_simple_async_result_get_source_tag (simple) ==
 624                   g_memory_output_stream_write_async);
 625
 626   nwritten = g_simple_async_result_get_op_res_gssize (simple);
 627
 628   return nwritten;
 629 }
 630
 631 static void
 632 g_memory_output_stream_close_async (GOutputStream       *stream,
 633                                     int                  io_priority,
 634                                     GCancellable        *cancellable,
 635                                     GAsyncReadyCallback  callback,
 636                                     gpointer             data)
 637 {
 638   GSimpleAsyncResult *simple;
 639
 640   simple = g_simple_async_result_new (G_OBJECT (stream),
 641                                       callback,
 642                                       data,
 643                                       g_memory_output_stream_close_async);
 644
 645
 646   /* will always return TRUE */
 647   g_memory_output_stream_close (stream, cancellable, NULL);
 648
 649   g_simple_async_result_complete_in_idle (simple);
 650   g_object_unref (simple);
 651 }
 652
 653 static gboolean
 654 g_memory_output_stream_close_finish (GOutputStream  *stream,
 655                                      GAsyncResult   *result,
 656                                      GError        **error)
 657 {
 658   GSimpleAsyncResult *simple;
 659
 660   simple = G_SIMPLE_ASYNC_RESULT (result);
 661
 662   g_warn_if_fail (g_simple_async_result_get_source_tag (simple) ==
 663                   g_memory_output_stream_close_async);
 664
 665   return TRUE;
 666 }
 667
 668 static goffset
 669 g_memory_output_stream_tell (GSeekable *seekable)
 670 {
 671   GMemoryOutputStream *stream;
 672   GMemoryOutputStreamPrivate *priv;
 673
 674   stream = G_MEMORY_OUTPUT_STREAM (seekable);
 675   priv = stream->priv;
 676
 677   return priv->pos;
 678 }
 679
 680 static gboolean
 681 g_memory_output_stream_can_seek (GSeekable *seekable)
 682 {
 683   return TRUE;
 684 }
 685
 686 static gboolean
 687 g_memory_output_stream_seek (GSeekable    *seekable,
 688                             goffset        offset,
 689                             GSeekType      type,
 690                             GCancellable  *cancellable,
 691                             GError       **error)
 692 {
 693   GMemoryOutputStream        *stream;
 694   GMemoryOutputStreamPrivate *priv;
 695   goffset absolute;
 696
 697   stream = G_MEMORY_OUTPUT_STREAM (seekable);
 698   priv = stream->priv;
 699
 700   switch (type)
 701     {
 702     case G_SEEK_CUR:
 703       absolute = priv->pos + offset;
 704       break;
 705
 706     case G_SEEK_SET:
 707       absolute = offset;
 708       break;
 709
 710     case G_SEEK_END:
 711       absolute = priv->len + offset;
 712       break;
 713
 714     default:
 715       g_set_error_literal (error,
 716                            G_IO_ERROR,
 717                            G_IO_ERROR_INVALID_ARGUMENT,
 718                            _("Invalid GSeekType supplied"));
 719
 720       return FALSE;
 721     }
 722
 723   if (absolute < 0)
 724     {
 725       g_set_error_literal (error,
 726                            G_IO_ERROR,
 727                            G_IO_ERROR_INVALID_ARGUMENT,
 728                            _("Requested seek before the beginning of the stream"));
 729       return FALSE;
 730     }
 731
 732   if (absolute > priv->len)
 733     {
 734       g_set_error_literal (error,
 735                            G_IO_ERROR,
 736                            G_IO_ERROR_INVALID_ARGUMENT,
 737                            _("Requested seek beyond the end of the stream"));
 738       return FALSE;
 739     }
 740
 741   priv->pos = absolute;
 742
 743   return TRUE;
 744 }
 745
 746 static gboolean
 747 g_memory_output_stream_can_truncate (GSeekable *seekable)
 748 {
 749   GMemoryOutputStream *ostream;
 750   GMemoryOutputStreamPrivate *priv;
 751
 752   ostream = G_MEMORY_OUTPUT_STREAM (seekable);
 753   priv = ostream->priv;
 754
 755   return priv->realloc_fn != NULL;
 756 }
 757
 758 static gboolean
 759 g_memory_output_stream_truncate (GSeekable     *seekable,
 760                                  goffset        offset,
 761                                  GCancellable  *cancellable,
 762                                  GError       **error)
 763 {
 764   GMemoryOutputStream *ostream = G_MEMORY_OUTPUT_STREAM (seekable);
 765
 766   if (!array_resize (ostream, offset, FALSE, error))
 767     return FALSE;
 768
 769   return TRUE;
 770 }
 771
 772 #define __G_MEMORY_OUTPUT_STREAM_C__
 773 #include "gioaliasdef.c"