control: add snd_ctl_elem_id_compare_numid() function

Idea for the function prototype by Takashi Sakamoto.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/include/control.h b/include/control.h
index 9e52f4c..386fbd7 100644 (file)
--- a/include/control.h
+++ b/include/control.h
@@ -424,6 +424,7 @@ int snd_ctl_elem_id_malloc(snd_ctl_elem_id_t **ptr);
 void snd_ctl_elem_id_free(snd_ctl_elem_id_t *obj);
 void snd_ctl_elem_id_clear(snd_ctl_elem_id_t *obj);
 void snd_ctl_elem_id_copy(snd_ctl_elem_id_t *dst, const snd_ctl_elem_id_t *src);
+int snd_ctl_elem_id_compare_numid(const snd_ctl_elem_id_t *id1, const snd_ctl_elem_id_t *id2);
 int snd_ctl_elem_id_compare_set(const snd_ctl_elem_id_t *id1, const snd_ctl_elem_id_t *id2);
 unsigned int snd_ctl_elem_id_get_numid(const snd_ctl_elem_id_t *obj);
 snd_ctl_elem_iface_t snd_ctl_elem_id_get_interface(const snd_ctl_elem_id_t *obj);

diff --git a/src/control/control.c b/src/control/control.c
index 3f98817..a3a32a1 100644 (file)
--- a/src/control/control.c
+++ b/src/control/control.c
@@ -1820,6 +1820,32 @@ void snd_ctl_elem_id_copy(snd_ctl_elem_id_t *dst, const snd_ctl_elem_id_t *src)
 }
 
 /**
+ * \brief compare one #snd_ctl_elem_id_t to another using numid
+ * \param id1 pointer to first id
+ * \param id2 pointer to second id
+ * \retval zero when values are identical, other value on a difference (like strcmp)
+ *
+ * This comparison ignores the set of fields part.
+ *
+ * The return value can be used for sorting like qsort(). It gives persistent
+ * results.
+ */
+int snd_ctl_elem_id_compare_numid(const snd_ctl_elem_id_t *id1, const snd_ctl_elem_id_t *id2)
+{
+       int64_t d;
+
+       assert(id1 && id2);
+       d = (int64_t)id1->numid - (int64_t)id2->numid;
+       if (d & ((int64_t)INT_MAX + 1)) {       /* fast path */
+               if (d > INT_MAX)
+                       d = INT_MAX;
+               else if (d < INT_MIN)
+                       d = INT_MIN;
+       }
+       return d;
+}
+
+/**
  * \brief compare one #snd_ctl_elem_id_t to another
  * \param id1 pointer to first id
  * \param id2 pointer to second id