MT#55283 add bencode_buffer_contains

Quick and unreliable test to see whether something is an allocation from
the buffer.

Change-Id: Ibbede22b3d6465db171cba55328b3625ed4c962d

daemon/bencode.c

@@ -134,6 +134,11 @@ alloc:
 	return ret;
 }
 
+bool bencode_buffer_contains(bencode_buffer_t *buf, const void *ptr) {
+	struct __bencode_buffer_piece *piece = buf->pieces;
+	return (ptr >= (void *) piece->buf && ptr < (void *) piece->tail);
+}
+
 void bencode_buffer_free(bencode_buffer_t *buf) {
 	struct __bencode_buffer_piece *piece, *next;
 

include/bencode.h

@@ -65,6 +65,9 @@ int bencode_buffer_init(bencode_buffer_t *buf);
 /* Allocate a piece of memory from the given buffer object */
 void *bencode_buffer_alloc(bencode_buffer_t *, size_t);
 
+// quick and non-reliable check whether the given pointer is from the buffer
+bool bencode_buffer_contains(bencode_buffer_t *, const void *);
+
 /* Destroys a previously initialized bencode_buffer_t object. All memory used by the object is freed
  * and all objects created through it become invalid. */
 void bencode_buffer_free(bencode_buffer_t *buf);