sapling/cfastmanifest/bsearch.c

// Copyright 2016-present Facebook. All Rights Reserved.
//
// bsearch.c: binary search implementation with context-aware callback.
//
// no-check-code

#include <stdio.h>
#include <stddef.h>

#include "bsearch.h"

size_t bsearch_between(const void *needle,
    const void *base, const size_t nel, const size_t width,
    int (*compare)(const void *needle,
        const void *fromarray,
        const void *context),
    const void *context) {
  ptrdiff_t start = 0;
  ptrdiff_t end = nel;

  while (start < end) {
    ptrdiff_t midpoint = start + ((end - start) / 2);

    if (midpoint == nel) {
      return nel;
    }

    const void *ptr = base + (midpoint * width);

    int cmp = compare(needle, ptr, context);

    if (cmp == 0) {
      return midpoint;
    } else if (cmp < 0) {
      end = midpoint;
    } else {
      start = midpoint + 1;
    }
  }

  return start;
}