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utils: Never return a group_id of 0, add GST_GROUP_ID_INVALID

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Various plugins use special values (0 or G_MAXUINT32) as an
invalid/unset group_id, but nothing guarantees a groupid won't have
that value.

Instead define a value which group_id will never have and make
gst_group_id_next() always return a value different from that.

API: GST_GROUP_ID_INVALID
This commit is contained in:
Edward Hervey 2017-12-05 17:28:55 +01:00 committed by Edward Hervey
parent 16d9954dd5
commit e5c15f6b96
3 changed files with 23 additions and 2 deletions
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1
docs/gst/gstreamer-sections.txt
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@ -3571,6 +3571,7 @@ GFLOAT_FROM_LE
GFLOAT_SWAP_LE_BE GFLOAT_SWAP_LE_BE
GFLOAT_TO_BE GFLOAT_TO_BE
GFLOAT_TO_LE GFLOAT_TO_LE
GST_GROUP_ID_INVALID
gst_guint64_to_gdouble gst_guint64_to_gdouble
gst_gdouble_to_guint64 gst_gdouble_to_guint64

12
gst/gstutils.c
View file

@ -4177,14 +4177,22 @@ gst_pad_get_stream (GstPad * pad)
* This function is used to generate a new group-id for the * This function is used to generate a new group-id for the
* stream-start event. * stream-start event.
* *
* This function never returns %GST_GROUP_ID_INVALID (which is 0)
*
* Returns: A constantly incrementing unsigned integer, which might * Returns: A constantly incrementing unsigned integer, which might
* overflow back to 0 at some point. * overflow back to 0 at some point.
*/ */
guint guint
gst_util_group_id_next (void) gst_util_group_id_next (void)
{ {
static gint counter = 0; static gint counter = 1;
return g_atomic_int_add (&counter, 1); gint ret = g_atomic_int_add (&counter, 1);
/* Make sure we don't return GST_GROUP_ID_INVALID */
if (G_UNLIKELY (ret == GST_GROUP_ID_INVALID))
ret = g_atomic_int_add (&counter, 1);
return ret;
} }
/* Compute log2 of the passed 64-bit number by finding the highest set bit */ /* Compute log2 of the passed 64-bit number by finding the highest set bit */

12
gst/gstutils.h
View file

@ -107,6 +107,18 @@ guint32 gst_util_seqnum_next (void);
GST_EXPORT GST_EXPORT
gint32 gst_util_seqnum_compare (guint32 s1, guint32 s2); gint32 gst_util_seqnum_compare (guint32 s1, guint32 s2);
/**
* GST_GROUP_ID_INVALID:
*
* A value which is guaranteed to never be returned by
* gst_util_group_id_next().
*
* Can be used as a default value in variables used to store group_id.
*
* Since: 1.14
*/
#define GST_GROUP_ID_INVALID (0)
GST_EXPORT GST_EXPORT
guint gst_util_group_id_next (void); guint gst_util_group_id_next (void);