fusl/src/locale/__mo_lookup.c

#include <stdint.h>
#include <string.h>

static inline uint32_t swapc(uint32_t x, int c) {
  return c ? x >> 24 | ((x >> 8) & 0xff00) | ((x << 8) & 0xff0000) | x << 24
           : x;
}

const char* __mo_lookup(const void* p, size_t size, const char* s) {
  const uint32_t* mo = p;
  int sw = *mo - 0x950412de;
  uint32_t b = 0, n = swapc(mo[2], sw);
  uint32_t o = swapc(mo[3], sw);
  uint32_t t = swapc(mo[4], sw);
  if (n >= size / 4 || o >= size - 4 * n || t >= size - 4 * n || ((o | t) % 4))
    return 0;
  o /= 4;
  t /= 4;
  for (;;) {
    uint32_t ol = swapc(mo[o + 2 * (b + n / 2)], sw);
    uint32_t os = swapc(mo[o + 2 * (b + n / 2) + 1], sw);
    if (os >= size || ol >= size - os || ((char*)p)[os + ol])
      return 0;
    int sign = strcmp(s, (char*)p + os);
    if (!sign) {
      uint32_t tl = swapc(mo[t + 2 * (b + n / 2)], sw);
      uint32_t ts = swapc(mo[t + 2 * (b + n / 2) + 1], sw);
      if (ts >= size || tl >= size - ts || ((char*)p)[ts + tl])
        return 0;
      return (char*)p + ts;
    } else if (n == 1)
      return 0;
    else if (sign < 0)
      n /= 2;
    else {
      b += n / 2;
      n -= n / 2;
    }
  }
  return 0;
}