Function mi_segment_commit_mask

3rd/mimalloc-2.0.9/src/segment.c:412–460

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static void mi_segment_commit_mask(mi_segment_t* segment, bool conservative, uint8_t* p, size_t size, uint8_t** start_p, size_t* full_size, mi_commit_mask_t* cm) {
  mi_assert_internal(_mi_ptr_segment(p + 1) == segment);
  mi_assert_internal(segment->kind != MI_SEGMENT_HUGE);
  mi_commit_mask_create_empty(cm);
  if (size == 0 || size > MI_SEGMENT_SIZE || segment->kind == MI_SEGMENT_HUGE) return;
  const size_t segstart = mi_segment_info_size(segment);
  const size_t segsize = mi_segment_size(segment);
  if (p >= (uint8_t*)segment + segsize) return;

  size_t pstart = (p - (uint8_t*)segment);
  mi_assert_internal(pstart + size <= segsize);

  size_t start;
  size_t end;
  if (conservative) {
    // decommit conservative
    start = _mi_align_up(pstart, MI_COMMIT_SIZE);
    end   = _mi_align_down(pstart + size, MI_COMMIT_SIZE);
    mi_assert_internal(start >= segstart);
    mi_assert_internal(end <= segsize);
  }
  else {
    // commit liberal
    start = _mi_align_down(pstart, MI_MINIMAL_COMMIT_SIZE);
    end   = _mi_align_up(pstart + size, MI_MINIMAL_COMMIT_SIZE);
  }
  if (pstart >= segstart && start < segstart) {  // note: the mask is also calculated for an initial commit of the info area
    start = segstart;
  }
  if (end > segsize) {
    end = segsize;
  }

  mi_assert_internal(start <= pstart && (pstart + size) <= end);
  mi_assert_internal(start % MI_COMMIT_SIZE==0 && end % MI_COMMIT_SIZE == 0);
  *start_p   = (uint8_t*)segment + start;
  *full_size = (end > start ? end - start : 0);
  if (*full_size == 0) return;

  size_t bitidx = start / MI_COMMIT_SIZE;
  mi_assert_internal(bitidx < MI_COMMIT_MASK_BITS);
  
  size_t bitcount = *full_size / MI_COMMIT_SIZE; // can be 0
  if (bitidx + bitcount > MI_COMMIT_MASK_BITS) {
    _mi_warning_message("commit mask overflow: idx=%zu count=%zu start=%zx end=%zx p=0x%p size=%zu fullsize=%zu\n", bitidx, bitcount, start, end, p, size, *full_size);
  }
  mi_assert_internal((bitidx + bitcount) <= MI_COMMIT_MASK_BITS);
  mi_commit_mask_create(bitidx, bitcount, cm);
}


static bool mi_segment_commitx(mi_segment_t* segment, bool commit, uint8_t* p, size_t size, mi_stats_t* stats) {