54 lines
1.6 KiB
C++
54 lines
1.6 KiB
C++
#pragma once
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#include "asl/integers.hpp"
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namespace asl::city_hash
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{
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// All CityHash stuff below this point
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// Hash function for a byte array.
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uint64_t CityHash64(const char *s, size_t len);
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// Hash function for a byte array. For convenience, a 64-bit seed is also
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// hashed into the result.
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uint64_t CityHash64WithSeed(const char *s, size_t len, uint64_t seed);
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// Hash function for a byte array. For convenience, two seeds are also
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// hashed into the result.
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uint64_t CityHash64WithSeeds(const char *s, size_t len,
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uint64_t seed0, uint64_t seed1);
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// Hash function for a byte array.
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uint128_t CityHash128(const char *s, size_t len);
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// Hash function for a byte array. For convenience, a 128-bit seed is also
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// hashed into the result.
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uint128_t CityHash128WithSeed(const char *s, size_t len, uint128_t seed);
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// Hash function for a byte array. Most useful in 32-bit binaries.
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uint32_t CityHash32(const char *s, size_t len);
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// Hash 128 input bits down to 64 bits of output.
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// This is intended to be a reasonably good hash function.
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constexpr uint64_t Hash128to64(uint64_t high, uint64_t low)
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{
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// Murmur-inspired hashing.
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const uint64_t kMul = 0x9ddfea08eb382d69ULL;
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uint64_t a = (low ^ high) * kMul;
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a ^= (a >> 47);
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uint64_t b = (high ^ a) * kMul;
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b ^= (b >> 47);
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b *= kMul;
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return b;
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}
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// Hash 128 input bits down to 64 bits of output.
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// This is intended to be a reasonably good hash function.
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constexpr uint64_t Hash128to64(const uint128_t& x)
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{
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return Hash128to64(x.high, x.low);
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}
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} // namespace asl::city_hash
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