MINOR: pattern: add pat_ref_gen_find_elt() function

pat_ref_gen_find_elt(ref, gen_id, key) tries to find <elt> element
belonging to <gen_id> and matching <key> in <ref> reference.

The goal is to be able to target a single subset from <ref>

Author: Darlelet

include/haproxy/pattern.h

@@ -184,6 +184,7 @@ struct pat_ref *pat_ref_lookupid(int unique_id);
 struct pat_ref *pat_ref_new(const char *reference, const char *display, unsigned int flags);
 struct pat_ref *pat_ref_newid(int unique_id, const char *display, unsigned int flags);
 struct pat_ref_elt *pat_ref_find_elt(struct pat_ref *ref, const char *key);
+struct pat_ref_elt *pat_ref_gen_find_elt(struct pat_ref *ref, unsigned int gen_id, const char *key);
 struct pat_ref_elt *pat_ref_append(struct pat_ref *ref, const char *pattern, const char *sample, int line);
 struct pat_ref_elt *pat_ref_load(struct pat_ref *ref, unsigned int gen, const char *pattern, const char *sample, int line, char **err);
 int pat_ref_push(struct pat_ref_elt *elt, struct pattern_expr *expr, int patflags, char **err);

src/pattern.c

@@ -1636,6 +1636,28 @@ int pat_ref_delete(struct pat_ref *ref, const char *key)
 	return found;
 }
 
+/*
+ * find and return an element <elt> belonging to <gen_id> and matching <key> in a
+ * reference <ref> return NULL if not found
+ */
+struct pat_ref_elt *pat_ref_gen_find_elt(struct pat_ref *ref, unsigned int gen_id, const char *key)
+{
+	struct ebmb_node *node;
+	struct pat_ref_elt *elt;
+
+	node = ebst_lookup(&ref->ebmb_root, key);
+	while (node) {
+		elt = ebmb_entry(node, struct pat_ref_elt, node);
+		if (elt->gen_id == gen_id)
+			break;
+		node = ebmb_next_dup(node);
+	}
+	if (node)
+		return ebmb_entry(node, struct pat_ref_elt, node);
+
+	return NULL;
+}
+
 /*
  * find and return an element <elt> matching <key> in a reference <ref>
  * return NULL if not found