Function _mi_segment_of

3rd/mimalloc-2.0.9/src/segment-cache.c:327–337

Determine the segment belonging to a pointer or NULL if it is not in a valid segment.

// Determine the segment belonging to a pointer or NULL if it is not in a valid segment.
static mi_segment_t* _mi_segment_of(const void* p) {
  if (p == NULL) return NULL;
  mi_segment_t* segment = _mi_ptr_segment(p);
  mi_assert_internal(segment != NULL);
  size_t bitidx;
  size_t index = mi_segment_map_index_of(segment, &bitidx);
  // fast path: for any pointer to valid small/medium/large object or first MI_SEGMENT_SIZE in huge
  const uintptr_t mask = mi_atomic_load_relaxed(&mi_segment_map[index]);
  if mi_likely((mask & ((uintptr_t)1 << bitidx)) != 0) {
    return segment; // yes, allocated by us
  }
  if (index==MI_SEGMENT_MAP_WSIZE) return NULL;

  // TODO: maintain max/min allocated range for efficiency for more efficient rejection of invalid pointers?