Justin Marshall
138 lines
3.6 KiB
C++
138 lines
3.6 KiB
C++
#include "murmur.h"
|
|
|
|
#include <cassert>
|
|
|
|
namespace {
|
|
|
|
constexpr std::uint32_t MURMUR_MULTIPLIER = 0x5BD1E995u;
|
|
|
|
std::uint32_t ReadLittleEndian32(const std::uint8_t* data) {
|
|
return static_cast<std::uint32_t>(data[0])
|
|
| (static_cast<std::uint32_t>(data[1]) << 8)
|
|
| (static_cast<std::uint32_t>(data[2]) << 16)
|
|
| (static_cast<std::uint32_t>(data[3]) << 24);
|
|
}
|
|
|
|
std::uint32_t ReadBigEndian32(const std::uint8_t* data) {
|
|
return (static_cast<std::uint32_t>(data[0]) << 24)
|
|
| (static_cast<std::uint32_t>(data[1]) << 16)
|
|
| (static_cast<std::uint32_t>(data[2]) << 8)
|
|
| static_cast<std::uint32_t>(data[3]);
|
|
}
|
|
|
|
std::uint32_t MixWord(std::uint32_t value) {
|
|
value *= MURMUR_MULTIPLIER;
|
|
value ^= value >> 24;
|
|
value *= MURMUR_MULTIPLIER;
|
|
return value;
|
|
}
|
|
|
|
} // namespace
|
|
|
|
std::uint32_t MurMur32_HashData(
|
|
const void* key,
|
|
const int length,
|
|
const std::uint32_t seed
|
|
) {
|
|
assert(length >= 0);
|
|
assert(key != nullptr || length == 0);
|
|
|
|
if (length < 0 || (key == nullptr && length != 0)) {
|
|
return 0;
|
|
}
|
|
|
|
const auto* data = static_cast<const std::uint8_t*>(key);
|
|
int remaining = length;
|
|
std::uint32_t hash = seed ^ static_cast<std::uint32_t>(length);
|
|
|
|
while (remaining >= 4) {
|
|
const std::uint32_t word = MixWord(ReadLittleEndian32(data));
|
|
hash = (hash * MURMUR_MULTIPLIER) ^ word;
|
|
data += 4;
|
|
remaining -= 4;
|
|
}
|
|
|
|
switch (remaining) {
|
|
case 3:
|
|
hash ^= static_cast<std::uint32_t>(data[2]) << 16;
|
|
// Fall through.
|
|
case 2:
|
|
hash ^= static_cast<std::uint32_t>(data[1]) << 8;
|
|
// Fall through.
|
|
case 1:
|
|
hash ^= data[0];
|
|
hash *= MURMUR_MULTIPLIER;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
hash ^= hash >> 13;
|
|
hash *= MURMUR_MULTIPLIER;
|
|
hash ^= hash >> 15;
|
|
return hash;
|
|
}
|
|
|
|
std::uint64_t MurMur64_HashData(
|
|
const void* key,
|
|
const int length,
|
|
const std::uint32_t seed
|
|
) {
|
|
assert(length >= 0);
|
|
assert(key != nullptr || length == 0);
|
|
|
|
if (length < 0 || (key == nullptr && length != 0)) {
|
|
return 0;
|
|
}
|
|
|
|
const auto* data = static_cast<const std::uint8_t*>(key);
|
|
int remaining = length;
|
|
std::uint32_t hash1 = seed ^ static_cast<std::uint32_t>(length);
|
|
std::uint32_t hash2 = 0;
|
|
|
|
// The recovered 360 function loads full words directly on big-endian PPC,
|
|
// but constructs its one-to-three-byte tail explicitly. Preserve that byte
|
|
// behavior so hashes continue to match the supplied Xbox resource data.
|
|
while (remaining >= 8) {
|
|
hash1 = (hash1 * MURMUR_MULTIPLIER)
|
|
^ MixWord(ReadBigEndian32(data));
|
|
hash2 = (hash2 * MURMUR_MULTIPLIER)
|
|
^ MixWord(ReadBigEndian32(data + 4));
|
|
data += 8;
|
|
remaining -= 8;
|
|
}
|
|
|
|
if (remaining >= 4) {
|
|
hash1 = (hash1 * MURMUR_MULTIPLIER)
|
|
^ MixWord(ReadBigEndian32(data));
|
|
data += 4;
|
|
remaining -= 4;
|
|
}
|
|
|
|
switch (remaining) {
|
|
case 3:
|
|
hash2 ^= static_cast<std::uint32_t>(data[2]) << 16;
|
|
// Fall through.
|
|
case 2:
|
|
hash2 ^= static_cast<std::uint32_t>(data[1]) << 8;
|
|
// Fall through.
|
|
case 1:
|
|
hash2 ^= data[0];
|
|
hash2 *= MURMUR_MULTIPLIER;
|
|
break;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
hash1 ^= hash2 >> 18;
|
|
hash1 *= MURMUR_MULTIPLIER;
|
|
hash2 ^= hash1 >> 22;
|
|
hash2 *= MURMUR_MULTIPLIER;
|
|
hash1 ^= hash2 >> 17;
|
|
hash1 *= MURMUR_MULTIPLIER;
|
|
hash2 ^= hash1 >> 19;
|
|
hash2 *= MURMUR_MULTIPLIER;
|
|
|
|
return (static_cast<std::uint64_t>(hash1) << 32) | hash2;
|
|
}
|