#include <stdint.h>
#include <stdlib.h>

#define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k))))

// clang-format off
#define mix(a,b,c) \
{ \
  a -= c;  a ^= rot(c, 4);  c += b; \
  b -= a;  b ^= rot(a, 6);  a += c; \
  c -= b;  c ^= rot(b, 8);  b += a; \
  a -= c;  a ^= rot(c,16);  c += b; \
  b -= a;  b ^= rot(a,19);  a += c; \
  c -= b;  c ^= rot(b, 4);  b += a; \
}

#define final(a,b,c) \
{ \
  c ^= b; c -= rot(b,14); \
  a ^= c; a -= rot(c,11); \
  b ^= a; b -= rot(a,25); \
  c ^= b; c -= rot(b,16); \
  a ^= c; a -= rot(c,4);  \
  b ^= a; b -= rot(a,14); \
  c ^= b; c -= rot(b,24); \
}
// clang-format on

uint32_t lookup3(const void *key, size_t length, uint32_t initval) {
    uint32_t        a, b, c;
    const uint8_t  *k;
    const uint32_t *data32Bit;

    data32Bit = key;
    a = b = c = 0xdeadbeef + (((uint32_t)length) << 2) + initval;

    while (length > 12) {
        a += *(data32Bit++);
        b += *(data32Bit++);
        c += *(data32Bit++);
        mix(a, b, c);
        length -= 12;
    }

    k = (const uint8_t *)data32Bit;
    switch (length) {
    case 12: c += ((uint32_t)k[11]) << 24;
    case 11: c += ((uint32_t)k[10]) << 16;
    case 10: c += ((uint32_t)k[9]) << 8;
    case 9: c += k[8];
    case 8: b += ((uint32_t)k[7]) << 24;
    case 7: b += ((uint32_t)k[6]) << 16;
    case 6: b += ((uint32_t)k[5]) << 8;
    case 5: b += k[4];
    case 4: a += ((uint32_t)k[3]) << 24;
    case 3: a += ((uint32_t)k[2]) << 16;
    case 2: a += ((uint32_t)k[1]) << 8;
    case 1: a += k[0]; break;
    case 0: return c;
    }
    final(a, b, c);
    return c;
}