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
  35 /**
  36  * SECTION:gmemoryoutputstream
  37  * @short_description: Streaming output operations on memory chunks
  38  * @include: gio/gio.h
  39  * @see_also: #GMemoryInputStream
  40  *
  41  * #GMemoryOutputStream is a class for using arbitrary
  42  * memory chunks as output for GIO streaming output operations.
  43  *
  44  */
  45
  46 #define MIN_ARRAY_SIZE  16
  47
  48 enum {
  49   PROP_0,
  50   PROP_DATA,
  51   PROP_SIZE,
  52   PROP_DATA_SIZE,
  53   PROP_REALLOC_FUNCTION,
  54   PROP_DESTROY_FUNCTION
  55 };
  56
  57 struct _GMemoryOutputStreamPrivate {
  58
  59   gpointer       data; /* Write buffer */
  60   gsize          len; /* Current length of the data buffer. Can change with resizing. */
  61   gsize          valid_len; /* The part of data that has been written to */
  62   gsize          pos; /* Current position in the stream. Distinct from valid_len,
  63                          because the stream is seekable. */
  64
  65   GReallocFunc   realloc_fn;
  66   GDestroyNotify destroy;
  67 };
  68
  69 static void     g_memory_output_stream_set_property (GObject      *object,
  70                                                      guint         prop_id,
  71                                                      const GValue *value,
  72                                                      GParamSpec   *pspec);
  73 static void     g_memory_output_stream_get_property (GObject      *object,
  74                                                      guint         prop_id,
  75                                                      GValue       *value,
  76                                                      GParamSpec   *pspec);
  77 static void     g_memory_output_stream_finalize     (GObject      *object);
  78
  79 static gssize   g_memory_output_stream_write       (GOutputStream *stream,
  80                                                     const void    *buffer,
  81                                                     gsize          count,
  82                                                     GCancellable  *cancellable,
  83                                                     GError       **error);
  84
  85 static gboolean g_memory_output_stream_close       (GOutputStream  *stream,
  86                                                     GCancellable   *cancellable,
  87                                                     GError        **error);
  88
  89 static void     g_memory_output_stream_write_async  (GOutputStream        *stream,
  90                                                      const void           *buffer,
  91                                                      gsize                 count,
  92                                                      int                   io_priority,
  93                                                      GCancellable         *cancellable,
  94                                                      GAsyncReadyCallback   callback,
  95                                                      gpointer              data);
  96 static gssize   g_memory_output_stream_write_finish (GOutputStream        *stream,
  97                                                      GAsyncResult         *result,
  98                                                      GError              **error);
  99 static void     g_memory_output_stream_close_async  (GOutputStream        *stream,
 100                                                      int                   io_priority,
 101                                                      GCancellable         *cancellable,
 102                                                      GAsyncReadyCallback   callback,
 103                                                      gpointer              data);
 104 static gboolean g_memory_output_stream_close_finish (GOutputStream        *stream,
 105                                                      GAsyncResult         *result,
 106                                                      GError              **error);
 107
 108 static void     g_memory_output_stream_seekable_iface_init (GSeekableIface  *iface);
 109 static goffset  g_memory_output_stream_tell                (GSeekable       *seekable);
 110 static gboolean g_memory_output_stream_can_seek            (GSeekable       *seekable);
 111 static gboolean g_memory_output_stream_seek                (GSeekable       *seekable,
 112                                                            goffset          offset,
 113                                                            GSeekType        type,
 114                                                            GCancellable    *cancellable,
 115                                                            GError         **error);
 116 static gboolean g_memory_output_stream_can_truncate        (GSeekable       *seekable);
 117 static gboolean g_memory_output_stream_truncate            (GSeekable       *seekable,
 118                                                            goffset          offset,
 119                                                            GCancellable    *cancellable,
 120                                                            GError         **error);
 121
 122 G_DEFINE_TYPE_WITH_CODE (GMemoryOutputStream, g_memory_output_stream, G_TYPE_OUTPUT_STREAM,
 123                          G_IMPLEMENT_INTERFACE (G_TYPE_SEEKABLE,
 124                                                 g_memory_output_stream_seekable_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   g_type_class_add_private (klass, sizeof (GMemoryOutputStreamPrivate));
 134
 135   gobject_class = G_OBJECT_CLASS (klass);
 136   gobject_class->set_property = g_memory_output_stream_set_property;
 137   gobject_class->get_property = g_memory_output_stream_get_property;
 138   gobject_class->finalize     = g_memory_output_stream_finalize;
 139
 140   ostream_class = G_OUTPUT_STREAM_CLASS (klass);
 141
 142   ostream_class->write_fn = g_memory_output_stream_write;
 143   ostream_class->close_fn = g_memory_output_stream_close;
 144   ostream_class->write_async  = g_memory_output_stream_write_async;
 145   ostream_class->write_finish = g_memory_output_stream_write_finish;
 146   ostream_class->close_async  = g_memory_output_stream_close_async;
 147   ostream_class->close_finish = g_memory_output_stream_close_finish;
 148
 149   /**
 150    * GMemoryOutputStream:data:
 151    *
 152    * Pointer to buffer where data will be written.
 153    *
 154    * Since: 2.24
 155    **/
 156   g_object_class_install_property (gobject_class,
 157                                    PROP_DATA,
 158                                    g_param_spec_pointer ("data",
 159                                                          P_("Data Buffer"),
 160                                                          P_("Pointer to buffer where data will be written."),
 161                                                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 162                                                          G_PARAM_STATIC_STRINGS));
 163
 164   /**
 165    * GMemoryOutputStream:size:
 166    *
 167    * Current size of the data buffer.
 168    *
 169    * Since: 2.24
 170    **/
 171   g_object_class_install_property (gobject_class,
 172                                    PROP_SIZE,
 173                                    g_param_spec_ulong ("size",
 174                                                        P_("Data Buffer Size"),
 175                                                        P_("Current size of the data buffer."),
 176                                                        0, G_MAXULONG, 0,
 177                                                        G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 178                                                        G_PARAM_STATIC_STRINGS));
 179
 180   /**
 181    * GMemoryOutputStream:data-size:
 182    *
 183    * Size of data written to the buffer.
 184    *
 185    * Since: 2.24
 186    **/
 187   g_object_class_install_property (gobject_class,
 188                                    PROP_DATA_SIZE,
 189                                    g_param_spec_ulong ("data-size",
 190                                                        P_("Data Size"),
 191                                                        P_("Size of data written to the buffer."),
 192                                                        0, G_MAXULONG, 0,
 193                                                        G_PARAM_READABLE |
 194                                                        G_PARAM_STATIC_STRINGS));
 195
 196   /**
 197    * GMemoryOutputStream:realloc-function:
 198    *
 199    * Function with realloc semantics called to enlarge the buffer.
 200    *
 201    * Since: 2.24
 202    **/
 203   g_object_class_install_property (gobject_class,
 204                                    PROP_REALLOC_FUNCTION,
 205                                    g_param_spec_pointer ("realloc-function",
 206                                                          P_("Memory Reallocation Function"),
 207                                                          P_("Function with realloc semantics called to enlarge the buffer."),
 208                                                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 209                                                          G_PARAM_STATIC_STRINGS));
 210
 211   /**
 212    * GMemoryOutputStream:destroy-function:
 213    *
 214    * Function called with the buffer as argument when the stream is destroyed.
 215    *
 216    * Since: 2.24
 217    **/
 218   g_object_class_install_property (gobject_class,
 219                                    PROP_DESTROY_FUNCTION,
 220                                    g_param_spec_pointer ("destroy-function",
 221                                                          P_("Destroy Notification Function"),
 222                                                          P_("Function called with the buffer as argument when the stream is destroyed."),
 223                                                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY |
 224                                                          G_PARAM_STATIC_STRINGS));
 225 }
 226
 227 static void
 228 g_memory_output_stream_set_property (GObject      *object,
 229                                      guint         prop_id,
 230                                      const GValue *value,
 231                                      GParamSpec   *pspec)
 232 {
 233   GMemoryOutputStream        *stream;
 234   GMemoryOutputStreamPrivate *priv;
 235
 236   stream = G_MEMORY_OUTPUT_STREAM (object);
 237   priv = stream->priv;
 238
 239   switch (prop_id)
 240     {
 241     case PROP_DATA:
 242       priv->data = g_value_get_pointer (value);
 243       break;
 244     case PROP_SIZE:
 245       priv->len = g_value_get_ulong (value);
 246       break;
 247     case PROP_REALLOC_FUNCTION:
 248       priv->realloc_fn = g_value_get_pointer (value);
 249       break;
 250     case PROP_DESTROY_FUNCTION:
 251       priv->destroy = g_value_get_pointer (value);
 252       break;
 253     default:
 254       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
 255       break;
 256     }
 257 }
 258
 259 static void
 260 g_memory_output_stream_get_property (GObject      *object,
 261                                      guint         prop_id,
 262                                      GValue       *value,
 263                                      GParamSpec   *pspec)
 264 {
 265   GMemoryOutputStream        *stream;
 266   GMemoryOutputStreamPrivate *priv;
 267
 268   stream = G_MEMORY_OUTPUT_STREAM (object);
 269   priv = stream->priv;
 270
 271   switch (prop_id)
 272     {
 273     case PROP_DATA:
 274       g_value_set_pointer (value, priv->data);
 275       break;
 276     case PROP_SIZE:
 277       g_value_set_ulong (value, priv->len);
 278       break;
 279     case PROP_DATA_SIZE:
 280       g_value_set_ulong (value, priv->valid_len);
 281       break;
 282     case PROP_REALLOC_FUNCTION:
 283       g_value_set_pointer (value, priv->realloc_fn);
 284       break;
 285     case PROP_DESTROY_FUNCTION:
 286       g_value_set_pointer (value, priv->destroy);
 287       break;
 288     default:
 289       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
 290       break;
 291     }
 292 }
 293
 294 static void
 295 g_memory_output_stream_finalize (GObject *object)
 296 {
 297   GMemoryOutputStream        *stream;
 298   GMemoryOutputStreamPrivate *priv;
 299
 300   stream = G_MEMORY_OUTPUT_STREAM (object);
 301   priv = stream->priv;
 302
 303   if (priv->destroy)
 304     priv->destroy (priv->data);
 305
 306   G_OBJECT_CLASS (g_memory_output_stream_parent_class)->finalize (object);
 307 }
 308
 309 static void
 310 g_memory_output_stream_seekable_iface_init (GSeekableIface *iface)
 311 {
 312   iface->tell         = g_memory_output_stream_tell;
 313   iface->can_seek     = g_memory_output_stream_can_seek;
 314   iface->seek         = g_memory_output_stream_seek;
 315   iface->can_truncate = g_memory_output_stream_can_truncate;
 316   iface->truncate_fn  = g_memory_output_stream_truncate;
 317 }
 318
 319
 320 static void
 321 g_memory_output_stream_init (GMemoryOutputStream *stream)
 322 {
 323   stream->priv = G_TYPE_INSTANCE_GET_PRIVATE (stream,
 324                                               G_TYPE_MEMORY_OUTPUT_STREAM,
 325                                               GMemoryOutputStreamPrivate);
 326   stream->priv->pos = 0;
 327   stream->priv->valid_len = 0;
 328 }
 329
 330 /**
 331  * g_memory_output_stream_new:
 332  * @data: pointer to a chunk of memory to use, or %NULL
 333  * @size: the size of @data
 334  * @realloc_function: a function with realloc() semantics (like g_realloc())
 335  *     to be called when @data needs to be grown, or %NULL
 336  * @destroy_function: a function to be called on @data when the stream is
 337  *     finalized, or %NULL
 338  *
 339  * Creates a new #GMemoryOutputStream.
 340  *
 341  * If @data is non-%NULL, the stream  will use that for its internal storage.
 342  * If @realloc_fn is non-%NULL, it will be used for resizing the internal
 343  * storage when necessary. To construct a fixed-size output stream,
 344  * pass %NULL as @realloc_fn.
 345  *
 346  * |[
 347  * /&ast; a stream that can grow &ast;/
 348  * stream = g_memory_output_stream_new (NULL, 0, realloc, free);
 349  *
 350  * /&ast; another stream that can grow &ast;/
 351  * stream2 = g_memory_output_stream_new (NULL, 0, g_realloc, g_free);
 352  *
 353  * /&ast; a fixed-size stream &ast;/
 354  * data = malloc (200);
 355  * stream3 = g_memory_output_stream_new (data, 200, NULL, free);
 356  * ]|
 357  *
 358  * Return value: A newly created #GMemoryOutputStream object.
 359  **/
 360 GOutputStream *
 361 g_memory_output_stream_new (gpointer       data,
 362                             gsize          size,
 363                             GReallocFunc   realloc_function,
 364                             GDestroyNotify destroy_function)
 365 {
 366   GOutputStream *stream;
 367
 368   stream = g_object_new (G_TYPE_MEMORY_OUTPUT_STREAM,
 369                          "data", data,
 370                          "size", size,
 371                          "realloc-function", realloc_function,
 372                          "destroy-function", destroy_function,
 373                          NULL);
 374
 375   return stream;
 376 }
 377
 378 /**
 379  * g_memory_output_stream_get_data:
 380  * @ostream: a #GMemoryOutputStream
 381  *
 382  * Gets any loaded data from the @ostream.
 383  *
 384  * Note that the returned pointer may become invalid on the next
 385  * write or truncate operation on the stream.
 386  *
 387  * Returns: pointer to the stream's data
 388  **/
 389 gpointer
 390 g_memory_output_stream_get_data (GMemoryOutputStream *ostream)
 391 {
 392   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), NULL);
 393
 394   return ostream->priv->data;
 395 }
 396
 397 /**
 398  * g_memory_output_stream_get_size:
 399  * @ostream: a #GMemoryOutputStream
 400  *
 401  * Gets the size of the currently allocated data area (availible from
 402  * g_memory_output_stream_get_data()). If the stream isn't
 403  * growable (no realloc was passed to g_memory_output_stream_new()) then
 404  * this is the maximum size of the stream and further writes
 405  * will return %G_IO_ERROR_NO_SPACE.
 406  *
 407  * Note that for growable streams the returned size may become invalid on
 408  * the next write or truncate operation on the stream.
 409  *
 410  * If you want the number of bytes currently written to the stream, use
 411  * g_memory_output_stream_get_data_size().
 412  *
 413  * Returns: the number of bytes allocated for the data buffer
 414  */
 415 gsize
 416 g_memory_output_stream_get_size (GMemoryOutputStream *ostream)
 417 {
 418   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
 419
 420   return ostream->priv->len;
 421 }
 422
 423 /**
 424  * g_memory_output_stream_get_data_size:
 425  * @ostream: a #GMemoryOutputStream
 426  *
 427  * Returns the number of bytes from the start up
 428  * to including the last byte written in the stream
 429  * that has not been truncated away.
 430  *
 431  * Returns: the number of bytes written to the stream
 432  *
 433  * Since: 2.18
 434  */
 435 gsize
 436 g_memory_output_stream_get_data_size (GMemoryOutputStream *ostream)
 437 {
 438   g_return_val_if_fail (G_IS_MEMORY_OUTPUT_STREAM (ostream), 0);
 439
 440   return ostream->priv->valid_len;
 441 }
 442
 443 static gboolean
 444 array_resize (GMemoryOutputStream  *ostream,
 445               gsize                 size,
 446               gboolean              allow_partial,
 447               GError              **error)
 448 {
 449   GMemoryOutputStreamPrivate *priv;
 450   gpointer data;
 451   gsize len;
 452
 453   priv = ostream->priv;
 454
 455   if (priv->len == size)
 456     return TRUE;
 457
 458   if (!priv->realloc_fn)
 459     {
 460       if (allow_partial &&
 461           priv->pos < priv->len)
 462         return TRUE; /* Short write */
 463
 464       g_set_error_literal (error,
 465                            G_IO_ERROR,
 466                            G_IO_ERROR_NO_SPACE,
 467                            _("Memory output stream not resizable"));
 468       return FALSE;
 469     }
 470
 471   len = priv->len;
 472   data = priv->realloc_fn (priv->data, size);
 473
 474   if (size > 0 && !data)
 475     {
 476       if (allow_partial &&
 477           priv->pos < priv->len)
 478         return TRUE; /* Short write */
 479
 480       g_set_error_literal (error,
 481                            G_IO_ERROR,
 482                            G_IO_ERROR_NO_SPACE,
 483                            _("Failed to resize memory output stream"));
 484       return FALSE;
 485     }
 486
 487   if (size > len)
 488     memset ((guint8 *)data + len, 0, size - len);
 489
 490   priv->data = data;
 491   priv->len = size;
 492
 493   if (priv->len < priv->valid_len)
 494     priv->valid_len = priv->len;
 495
 496   return TRUE;
 497 }
 498
 499 static gint
 500 g_nearest_pow (gint num)
 501 {
 502   gint n = 1;
 503
 504   while (n < num)
 505     n <<= 1;
 506
 507   return n;
 508 }
 509
 510 static gssize
 511 g_memory_output_stream_write (GOutputStream  *stream,
 512                               const void     *buffer,
 513                               gsize           count,
 514                               GCancellable   *cancellable,
 515                               GError        **error)
 516 {
 517   GMemoryOutputStream        *ostream;
 518   GMemoryOutputStreamPrivate *priv;
 519   guint8   *dest;
 520   gsize new_size;
 521
 522   ostream = G_MEMORY_OUTPUT_STREAM (stream);
 523   priv = ostream->priv;
 524
 525   if (count == 0)
 526     return 0;
 527
 528   /* Check for address space overflow, but only if the buffer is resizable.
 529      Otherwise we just do a short write and don't worry. */
 530   if (priv->realloc_fn && priv->pos + count < priv->pos)
 531     goto overflow;
 532
 533   if (priv->pos + count > priv->len)
 534     {
 535       /* At least enought to fit the write, rounded up
 536              for greater than linear growth.
 537          TODO: This wastes a lot of memory at large stream sizes.
 538                Figure out a more rational allocation strategy. */
 539       new_size = g_nearest_pow (priv->pos + count);
 540       /* Check for overflow again. We have only checked if
 541          pos + count > G_MAXSIZE, but it only catches the case of writing
 542          more than 4GiB total on a 32-bit system. There's still the problem
 543          of g_nearest_pow overflowing above 0x7fffffff, so we're
 544          effectively limited to 2GiB. */
 545       if (new_size < priv->len)
 546         goto overflow;
 547
 548       new_size = MAX (new_size, MIN_ARRAY_SIZE);
 549       if (!array_resize (ostream, new_size, TRUE, error))
 550         return -1;
 551     }
 552
 553   /* Make sure we handle short writes if the array_resize
 554      only added part of the required memory */
 555   count = MIN (count, priv->len - priv->pos);
 556
 557   dest = (guint8 *)priv->data + priv->pos;
 558   memcpy (dest, buffer, count);
 559   priv->pos += count;
 560
 561   if (priv->pos > priv->valid_len)
 562     priv->valid_len = priv->pos;
 563
 564   return count;
 565
 566  overflow:
 567   /* Overflow: buffer size would need to be bigger than G_MAXSIZE. */
 568   g_set_error_literal (error,
 569                        G_IO_ERROR,
 570                        G_IO_ERROR_NO_SPACE,
 571                        _("Amount of memory required to process the write is "
 572                          "larger than available address space"));
 573   return -1;
 574 }
 575
 576 static gboolean
 577 g_memory_output_stream_close (GOutputStream  *stream,
 578                               GCancellable   *cancellable,
 579                               GError        **error)
 580 {
 581   return TRUE;
 582 }
 583
 584 static void
 585 g_memory_output_stream_write_async (GOutputStream       *stream,
 586                                     const void          *buffer,
 587                                     gsize                count,
 588                                     int                  io_priority,
 589                                     GCancellable        *cancellable,
 590                                     GAsyncReadyCallback  callback,
 591                                     gpointer             data)
 592 {
 593   GSimpleAsyncResult *simple;
 594   gssize nwritten;
 595
 596   nwritten = g_memory_output_stream_write (stream,
 597                                            buffer,
 598                                            count,
 599                                            cancellable,
 600                                            NULL);
 601
 602   simple = g_simple_async_result_new (G_OBJECT (stream),
 603                                       callback,
 604                                       data,
 605                                       g_memory_output_stream_write_async);
 606
 607   g_simple_async_result_set_op_res_gssize (simple, nwritten);
 608   g_simple_async_result_complete_in_idle (simple);
 609   g_object_unref (simple);
 610 }
 611
 612 static gssize
 613 g_memory_output_stream_write_finish (GOutputStream  *stream,
 614                                      GAsyncResult   *result,
 615                                      GError        **error)
 616 {
 617   GSimpleAsyncResult *simple;
 618   gssize nwritten;
 619
 620   simple = G_SIMPLE_ASYNC_RESULT (result);
 621
 622   g_warn_if_fail (g_simple_async_result_get_source_tag (simple) ==
 623                   g_memory_output_stream_write_async);
 624
 625   nwritten = g_simple_async_result_get_op_res_gssize (simple);
 626
 627   return nwritten;
 628 }
 629
 630 static void
 631 g_memory_output_stream_close_async (GOutputStream       *stream,
 632                                     int                  io_priority,
 633                                     GCancellable        *cancellable,
 634                                     GAsyncReadyCallback  callback,
 635                                     gpointer             data)
 636 {
 637   GSimpleAsyncResult *simple;
 638
 639   simple = g_simple_async_result_new (G_OBJECT (stream),
 640                                       callback,
 641                                       data,
 642                                       g_memory_output_stream_close_async);
 643
 644
 645   /* will always return TRUE */
 646   g_memory_output_stream_close (stream, cancellable, NULL);
 647
 648   g_simple_async_result_complete_in_idle (simple);
 649   g_object_unref (simple);
 650 }
 651
 652 static gboolean
 653 g_memory_output_stream_close_finish (GOutputStream  *stream,
 654                                      GAsyncResult   *result,
 655                                      GError        **error)
 656 {
 657   GSimpleAsyncResult *simple;
 658
 659   simple = G_SIMPLE_ASYNC_RESULT (result);
 660
 661   g_warn_if_fail (g_simple_async_result_get_source_tag (simple) ==
 662                   g_memory_output_stream_close_async);
 663
 664   return TRUE;
 665 }
 666
 667 static goffset
 668 g_memory_output_stream_tell (GSeekable *seekable)
 669 {
 670   GMemoryOutputStream *stream;
 671   GMemoryOutputStreamPrivate *priv;
 672
 673   stream = G_MEMORY_OUTPUT_STREAM (seekable);
 674   priv = stream->priv;
 675
 676   return priv->pos;
 677 }
 678
 679 static gboolean
 680 g_memory_output_stream_can_seek (GSeekable *seekable)
 681 {
 682   return TRUE;
 683 }
 684
 685 static gboolean
 686 g_memory_output_stream_seek (GSeekable    *seekable,
 687                             goffset        offset,
 688                             GSeekType      type,
 689                             GCancellable  *cancellable,
 690                             GError       **error)
 691 {
 692   GMemoryOutputStream        *stream;
 693   GMemoryOutputStreamPrivate *priv;
 694   goffset absolute;
 695
 696   stream = G_MEMORY_OUTPUT_STREAM (seekable);
 697   priv = stream->priv;
 698
 699   switch (type)
 700     {
 701     case G_SEEK_CUR:
 702       absolute = priv->pos + offset;
 703       break;
 704
 705     case G_SEEK_SET:
 706       absolute = offset;
 707       break;
 708
 709     case G_SEEK_END:
 710       absolute = priv->len + offset;
 711       break;
 712
 713     default:
 714       g_set_error_literal (error,
 715                            G_IO_ERROR,
 716                            G_IO_ERROR_INVALID_ARGUMENT,
 717                            _("Invalid GSeekType supplied"));
 718
 719       return FALSE;
 720     }
 721
 722   if (absolute < 0)
 723     {
 724       g_set_error_literal (error,
 725                            G_IO_ERROR,
 726                            G_IO_ERROR_INVALID_ARGUMENT,
 727                            _("Requested seek before the beginning of the stream"));
 728       return FALSE;
 729     }
 730
 731   if (absolute > priv->len)
 732     {
 733       g_set_error_literal (error,
 734                            G_IO_ERROR,
 735                            G_IO_ERROR_INVALID_ARGUMENT,
 736                            _("Requested seek beyond the end of the stream"));
 737       return FALSE;
 738     }
 739
 740   priv->pos = absolute;
 741
 742   return TRUE;
 743 }
 744
 745 static gboolean
 746 g_memory_output_stream_can_truncate (GSeekable *seekable)
 747 {
 748   GMemoryOutputStream *ostream;
 749   GMemoryOutputStreamPrivate *priv;
 750
 751   ostream = G_MEMORY_OUTPUT_STREAM (seekable);
 752   priv = ostream->priv;
 753
 754   return priv->realloc_fn != NULL;
 755 }
 756
 757 static gboolean
 758 g_memory_output_stream_truncate (GSeekable     *seekable,
 759                                  goffset        offset,
 760                                  GCancellable  *cancellable,
 761                                  GError       **error)
 762 {
 763   GMemoryOutputStream *ostream = G_MEMORY_OUTPUT_STREAM (seekable);
 764
 765   if (!array_resize (ostream, offset, FALSE, error))
 766     return FALSE;
 767
 768   return TRUE;
 769 }