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manual: Fix examples to check for gst_buffer_map return values

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Otherwise people reading the manual will expect it to always
succeed :)

https://bugzilla.gnome.org/show_bug.cgi?id=728326
This commit is contained in:
Edward Hervey 2014-04-16 11:42:18 +02:00 committed by Edward Hervey
parent 1f7fba19f7
commit 01ad1fb343
1 changed files with 27 additions and 18 deletions
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45
docs/manual/advanced-dataaccess.xml
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@ -164,20 +164,27 @@ cb_have_data (GstPad *pad,
buffer = GST_PAD_PROBE_INFO_BUFFER (info); buffer = GST_PAD_PROBE_INFO_BUFFER (info);
buffer = gst_buffer_make_writable (buffer); buffer = gst_buffer_make_writable (buffer);
gst_buffer_map (buffer, &map, GST_MAP_WRITE);
ptr = (guint16 *) map.data; /* Making a buffer writable can fail (for example if it
/* invert data */ * cannot be copied and is used more than once)
for (y = 0; y < 288; y++) { */
for (x = 0; x < 384 / 2; x++) { if (buffer == NULL)
t = ptr[384 - 1 - x]; return GST_PAD_PROBE_OK;
ptr[384 - 1 - x] = ptr[x];
ptr[x] = t; /* Mapping a buffer can fail (non-writable) */
if (gst_buffer_map (buffer, &map, GST_MAP_WRITE)) {
ptr = (guint16 *) map.data;
/* invert data */
for (y = 0; y < 288; y++) {
for (x = 0; x < 384 / 2; x++) {
t = ptr[384 - 1 - x];
ptr[384 - 1 - x] = ptr[x];
ptr[x] = t;
}
ptr += 384;
} }
ptr += 384; gst_buffer_unmap (buffer, &map);
} }
gst_buffer_unmap (buffer, &map);
GST_PAD_PROBE_INFO_DATA (info) = buffer; GST_PAD_PROBE_INFO_DATA (info) = buffer;
@ -995,16 +1002,18 @@ main (int argc, char *argv[])
/* create pixmap from buffer and save, gstreamer video buffers have a stride /* create pixmap from buffer and save, gstreamer video buffers have a stride
* that is rounded up to the nearest multiple of 4 */ * that is rounded up to the nearest multiple of 4 */
buffer = gst_sample_get_buffer (sample); buffer = gst_sample_get_buffer (sample);
gst_buffer_map (buffer, &map, GST_MAP_READ); /* Mapping a buffer can fail (non-readable) */
if (gst_buffer_map (buffer, &map, GST_MAP_READ)) {
#ifdef HAVE_GTK #ifdef HAVE_GTK
pixbuf = gdk_pixbuf_new_from_data (map.data, pixbuf = gdk_pixbuf_new_from_data (map.data,
GDK_COLORSPACE_RGB, FALSE, 8, width, height, GDK_COLORSPACE_RGB, FALSE, 8, width, height,
GST_ROUND_UP_4 (width * 3), NULL, NULL); GST_ROUND_UP_4 (width * 3), NULL, NULL);
/* save the pixbuf */ /* save the pixbuf */
gdk_pixbuf_save (pixbuf, "snapshot.png", "png", &error, NULL); gdk_pixbuf_save (pixbuf, "snapshot.png", "png", &error, NULL);
#endif #endif
gst_buffer_unmap (buffer, &map); gst_buffer_unmap (buffer, &map);
}
gst_sample_unref (sample); gst_sample_unref (sample);
} else { } else {
g_print ("could not make snapshot\n"); g_print ("could not make snapshot\n");