Function extents_fit_alignment

deps/jemalloc/src/extent.c:405–436

* Find an extent with size [min_size, max_size) to satisfy the alignment * requirement. For each size, try only the first extent in the heap. */

 * requirement.  For each size, try only the first extent in the heap.
 */
static extent_t *
extents_fit_alignment(extents_t *extents, size_t min_size, size_t max_size,
    size_t alignment) {
        pszind_t pind = sz_psz2ind(extent_size_quantize_ceil(min_size));
        pszind_t pind_max = sz_psz2ind(extent_size_quantize_ceil(max_size));

	for (pszind_t i = (pszind_t)bitmap_ffu(extents->bitmap,
	    &extents_bitmap_info, (size_t)pind); i < pind_max; i =
	    (pszind_t)bitmap_ffu(extents->bitmap, &extents_bitmap_info,
	    (size_t)i+1)) {
		assert(i < SC_NPSIZES);
		assert(!extent_heap_empty(&extents->heaps[i]));
		extent_t *extent = extent_heap_first(&extents->heaps[i]);
		uintptr_t base = (uintptr_t)extent_base_get(extent);
		size_t candidate_size = extent_size_get(extent);
		assert(candidate_size >= min_size);

		uintptr_t next_align = ALIGNMENT_CEILING((uintptr_t)base,
		    PAGE_CEILING(alignment));
		if (base > next_align || base + candidate_size <= next_align) {
			/* Overflow or not crossing the next alignment. */
			continue;
		}

		size_t leadsize = next_align - base;
		if (candidate_size - leadsize >= min_size) {
			return extent;
		}
	}

	return NULL;
}

/*
 * Do first-fit extent selection, i.e. select the oldest/lowest extent that is