idxset: Add set contains() function

This is functionally equivalent to get_by_data(s, p, NULL) == p, but
with a more obvious name and form because some existing code is instead
manually iterating through idxsets to check for existence of an item.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/596>

src/pulsecore/idxset.c

@@ -258,6 +258,20 @@ void* pa_idxset_get_by_data(pa_idxset*s, const void *p, uint32_t *idx) {
     return e->data;
 }
 
+bool pa_idxset_contains(pa_idxset *s, const void *p) {
+    unsigned hash;
+    struct idxset_entry *e;
+
+    pa_assert(s);
+
+    hash = s->hash_func(p) % NBUCKETS;
+
+    if (!(e = data_scan(s, hash, p)))
+        return false;
+
+    return e->data == p;
+}
+
 void* pa_idxset_remove_by_index(pa_idxset*s, uint32_t idx) {
     struct idxset_entry *e;
     unsigned hash;

src/pulsecore/idxset.h

@@ -66,6 +66,9 @@ void* pa_idxset_get_by_index(pa_idxset*s, uint32_t idx);
 /* Get the entry by its data. The index is returned in *idx */
 void* pa_idxset_get_by_data(pa_idxset*s, const void *p, uint32_t *idx);
 
+/* Return true if item is in idxset */
+bool pa_idxset_contains(pa_idxset *s, const void *p);
+
 /* Similar to pa_idxset_get_by_index(), but removes the entry from the idxset. */
 void* pa_idxset_remove_by_index(pa_idxset*s, uint32_t idx);