gdk_pixbuf_new_from_stream

[Martin Kalbfuß <ma kalbfuss web de>]

I wrote a small test application to check the behavior of
gdk_pixbuf_new_from_stream. It writes two pixbufs into a stream and then
tries to read them. png is used as format. The first png is loaded as
expected. But the second is not. Other reading operations fail, too. The
stream isn't readable any longer after gdk_pixbuf_new_from_stream.
That's a big problem, because this is the most important part of my
nearly finished application. Any ideas what I can do about it?

gtk version is 2.18.6

#include <gdk-pixbuf/gdk-pixbuf.h>
#include <gio/gio.h>
#include <stdlib.h>

gint main(void)
{
  GError            * error = NULL;
  GFile             * file;
  GFileOutputStream * output_stream;
  GFileInputStream  * input_stream;
  GdkPixbuf         * pixbuf;
  gboolean            ret;

  g_type_init();

  file = g_file_new_for_path("./test.dat");

  output_stream = g_file_replace(file, NULL, FALSE, 0, NULL, &error);

  if (output_stream == NULL)
    {
      g_printerr("%s\n", error->message);
      exit(EXIT_FAILURE);
    }

  pixbuf = gdk_pixbuf_new_from_file("test.png", &error);

  if (pixbuf == NULL)
    {
      g_printerr("%s\n", error->message);
      exit(EXIT_FAILURE);
    }


  ret = gdk_pixbuf_save_to_stream(pixbuf,
G_OUTPUT_STREAM(output_stream),
				  "png", NULL, &error, NULL);

  if (ret == FALSE)
    {
      g_printerr("%s\n", error->message);
      exit(EXIT_FAILURE);
    }

  ret = gdk_pixbuf_save_to_stream(pixbuf,
G_OUTPUT_STREAM(output_stream),
				  "png", NULL, &error, NULL);

  if (ret == FALSE)
    {
      g_printerr("%s\n", error->message);
      exit(EXIT_FAILURE);
    }

  g_output_stream_close(G_OUTPUT_STREAM(output_stream), NULL, NULL);

  input_stream = g_file_read(file, NULL, &error);

  if (input_stream == NULL)
    {
      g_printerr("%s\n", error->message);
      exit(EXIT_FAILURE);
    }

  g_object_unref(pixbuf);

  pixbuf = gdk_pixbuf_new_from_stream(G_INPUT_STREAM(input_stream),
NULL,
				      &error);

  if (pixbuf == NULL)
    {
      g_printerr("1st read: %s\n", error->message);
      exit(EXIT_FAILURE);
    }

  g_object_unref(pixbuf);

  pixbuf = gdk_pixbuf_new_from_stream(G_INPUT_STREAM(input_stream),
NULL,
				      &error);

  if (pixbuf == NULL)
    {
      g_printerr("2nd read: %s\n", error->message);
      exit(EXIT_FAILURE);
    }

  g_input_stream_close(G_INPUT_STREAM(input_stream), NULL, NULL);

  exit(EXIT_SUCCESS);
}



file content after the writing operations:

00000000   89 50 4E 47  0D 0A 1A 0A  00 00 00 0D  49 48 44
52  .PNG........IHDR
00000010   00 00 00 10  00 00 00 10  08 02 00 00  00 90 91
68  ...............h
00000020   36 00 00 00  03 73 42 49  54 08 08 08  DB E1 4F E0
6....sBIT.....O.
00000030   00 00 00 40  49 44 41 54  28 91 63 60  20 11 30
32      IDAT(.c` .02
00000040   30 30 EC 2B  20 56 B5 D3  04 06 16 06  06 86 A6 6D  00.+
V.........m
00000050   0C 6E 9A 84  55 5B 28 32  30 30 30 30  91 EA A4
51  .n..U[(20000...Q
00000060   0D 23 45 03  23 03 03 83  83 1A B1 AA  0F DC 22
D5  .#E.#.........".
00000070   7C 06 06 00  81 CA 06 1D  01 B7 D6 31  00 00 00 00
|..........1....
00000080   49 45 4E 44  AE 42 60 82  89 50 4E 47  0D 0A 1A 0A
IEND.B`..PNG....
00000090   00 00 00 0D  49 48 44 52  00 00 00 10  00 00 00
10  ....IHDR........
000000A0   08 02 00 00  00 90 91 68  36 00 00 00  03 73 42
49  .......h6....sBI
000000B0   54 08 08 08  DB E1 4F E0  00 00 00 40  49 44 41 54
T     O     IDAT
000000C0   28 91 63 60  20 11 30 32  30 30 EC 2B  20 56 B5 D3
(.c` .0200.+ V..
000000D0   04 06 16 06  06 86 A6 6D  0C 6E 9A 84  55 5B 28
32  .......m.n..U[(2
000000E0   30 30 30 30  91 EA A4 51  0D 23 45 03  23 03 03 83
0000...Q.#E.#...
000000F0   83 1A B1 AA  0F DC 22 D5  7C 06 06 00  81 CA 06
1D  ......".|.......
00000100   01 B7 D6 31  00 00 00 00  49 45 4E 44  AE 42 60
82  ...1....IEND.B`.