1 /*
2   malloc_usable_size - fully inspired by musl implementation
3 */
4 
5 #include "malloc.h"
6 
7 /* for malloc_usable_size  */
8 #define OVERHEAD (2*sizeof(size_t))
9 #define CHUNK_SIZE(c) ((c)->size & -2)
10 #define MEM_TO_CHUNK(p) (struct malloc_chunk *)((char *)(p) - OVERHEAD)
11 
malloc_usable_size(void * p)12 size_t malloc_usable_size(void *p) {
13 	return p ? CHUNK_SIZE(MEM_TO_CHUNK(p)) - OVERHEAD : 0;
14 }
15