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/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
#include <cstddef>
#include <cstdint>
#include <cstring>
#include "misc/MurmurHash.h"
using namespace antlr4::misc;
// A variation of the MurmurHash3 implementation (https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp)
// Here we unrolled the loop used there into individual calls to update(), as we usually hash object fields
// instead of entire buffers.
// Platform-specific functions and macros
// Microsoft Visual Studio
#if defined(_MSC_VER)
#include <stdlib.h>
#define ROTL32(x,y) _rotl(x,y)
#define ROTL64(x,y) _rotl64(x,y)
#elif ANTLR4CPP_HAVE_BUILTIN(__builtin_rotateleft32) && ANTLR4CPP_HAVE_BUILTIN(__builtin_rotateleft64)
#define ROTL32(x, y) __builtin_rotateleft32(x, y)
#define ROTL64(x, y) __builtin_rotateleft64(x, y)
#else // defined(_MSC_VER)
// Other compilers
namespace {
constexpr uint32_t ROTL32(uint32_t x, int r) {
return (x << r) | (x >> (32 - r));
}
constexpr uint64_t ROTL64(uint64_t x, int r) {
return (x << r) | (x >> (64 - r));
}
}
#endif // !defined(_MSC_VER)
#if SIZE_MAX == UINT64_MAX
size_t MurmurHash::update(size_t hash, size_t value) {
size_t k1 = value;
k1 *= UINT64_C(0x87c37b91114253d5);
k1 = ROTL64(k1, 31);
k1 *= UINT64_C(0x4cf5ad432745937f);
hash ^= k1;
hash = ROTL64(hash, 27);
hash = hash * 5 + UINT64_C(0x52dce729);
return hash;
}
size_t MurmurHash::finish(size_t hash, size_t entryCount) {
hash ^= entryCount * 8;
hash ^= hash >> 33;
hash *= UINT64_C(0xff51afd7ed558ccd);
hash ^= hash >> 33;
hash *= UINT64_C(0xc4ceb9fe1a85ec53);
hash ^= hash >> 33;
return hash;
}
#elif SIZE_MAX == UINT32_MAX
size_t MurmurHash::update(size_t hash, size_t value) {
size_t k1 = value;
k1 *= UINT32_C(0xCC9E2D51);
k1 = ROTL32(k1, 15);
k1 *= UINT32_C(0x1B873593);
hash ^= k1;
hash = ROTL32(hash, 13);
hash = hash * 5 + UINT32_C(0xE6546B64);
return hash;
}
size_t MurmurHash::finish(size_t hash, size_t entryCount) {
hash ^= entryCount * 4;
hash ^= hash >> 16;
hash *= UINT32_C(0x85EBCA6B);
hash ^= hash >> 13;
hash *= UINT32_C(0xC2B2AE35);
hash ^= hash >> 16;
return hash;
}
#else
#error "Expected sizeof(size_t) to be 4 or 8."
#endif
size_t MurmurHash::update(size_t hash, const void *data, size_t size) {
size_t value;
const uint8_t *bytes = static_cast<const uint8_t*>(data);
while (size >= sizeof(size_t)) {
std::memcpy(&value, bytes, sizeof(size_t));
hash = update(hash, value);
bytes += sizeof(size_t);
size -= sizeof(size_t);
}
if (size != 0) {
value = 0;
std::memcpy(&value, bytes, size);
hash = update(hash, value);
}
return hash;
}
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