60 lines
1.5 KiB
C++
60 lines
1.5 KiB
C++
#ifndef __CXXMPH_RANDOMLY_SEEDED_HASH__
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#define __CXXMPH_RANDOMLY_SEEDED_HASH__
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// Helper to create randomly seeded hash functions out of existing hash
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// functions that take a seed as a parameter.
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#include <cstdlib>
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#include "../src/cmph_types.h"
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#include "MurmurHash2.h"
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#include "jenkins_hash.h"
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#include "stringpiece.h"
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namespace cxxmph {
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template <class HashFun>
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struct RandomlySeededHashFunction { };
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class JenkinsStringPiece { };
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class Murmur2StringPiece { };
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class Murmur2Pod { };
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template <>
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struct RandomlySeededHashFunction<JenkinsStringPiece> {
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RandomlySeededHashFunction() {
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srand(1);
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seed = 4;
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}
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cmph_uint32 operator()(const StringPiece& key) const {
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return jenkins_hash(key.data(), key.length(), seed);
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}
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void operator()(const StringPiece& key, cmph_uint32* hashes) const {
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__jenkins_hash_vector(seed, key.data(), key.length(), hashes);
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}
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cmph_uint32 seed;
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};
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template <>
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struct RandomlySeededHashFunction<Murmur2StringPiece> {
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RandomlySeededHashFunction() : seed(random()) { }
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cmph_uint32 operator()(const StringPiece& key) const {
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return MurmurHash2(key.data(), key.length(), seed);
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}
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cmph_uint32 seed;
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};
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template<>
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struct RandomlySeededHashFunction<Murmur2Pod> {
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RandomlySeededHashFunction() : seed(random()) { }
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template<class Key>
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cmph_uint32 operator()(const Key& key) const {
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return MurmurHash2(&key, sizeof(key), seed);
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}
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cmph_uint32 seed;
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};
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} // namespace cxxmph
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#endif // __CXXMPH_RANDOMLY_SEEDED_HASH__
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