97 lines
3.2 KiB
C++
97 lines
3.2 KiB
C++
#ifndef __CXXMPH_SEEDED_HASH_H__
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#define __CXXMPH_SEEDED_HASH_H__
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#include <stdint.h> // for uint32_t and friends
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#include <cstdlib>
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#include <unordered_map> // for std::hash
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#include "MurmurHash2.h"
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#include "stringpiece.h"
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namespace cxxmph {
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template <class HashFcn>
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struct seeded_hash_function {
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template <class Key>
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uint32_t operator()(const Key& k, uint32_t seed) const {
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return HashFcn()(k) ^ seed;
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}
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};
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struct seeded_identity_function {
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template <class Key>
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uint32_t operator()(const Key& k, uint32_t seed) const {
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return k ^ seed;
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}
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};
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struct Murmur2 {
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template<class Key>
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uint32_t operator()(const Key& k) const {
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return MurmurHash2(reinterpret_cast<const void*>(&k), sizeof(Key), 1 /* seed */);
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}
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};
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struct Murmur2StringPiece {
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template <class Key>
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uint32_t operator()(const Key& k) const {
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StringPiece s(k);
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return MurmurHash2(s.data(), s.length(), 1 /* seed */);
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}
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};
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template <>
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struct seeded_hash_function<Murmur2> {
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template <class Key>
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uint32_t operator()(const Key& k, uint32_t seed) const {
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return MurmurHash2(reinterpret_cast<const void*>(&k), sizeof(Key), seed);
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}
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};
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template <>
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struct seeded_hash_function<Murmur2StringPiece> {
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template <class Key>
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uint32_t operator()(const Key& k, uint32_t seed) const {
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StringPiece s(k);
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return MurmurHash2(s.data(), s.length(), seed);
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}
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};
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template <class HashFcn> struct seeded_hash
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{ typedef seeded_hash_function<HashFcn> hash_function; };
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// Use Murmur2 instead for all types defined in std::hash, plus
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// std::string which is commonly extended.
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template <> struct seeded_hash<std::hash<char*> >
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{ typedef seeded_hash_function<Murmur2StringPiece> hash_function; };
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template <> struct seeded_hash<std::hash<const char*> >
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{ typedef seeded_hash_function<Murmur2StringPiece> hash_function; };
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template <> struct seeded_hash<std::hash<std::string> >
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{ typedef seeded_hash_function<Murmur2StringPiece> hash_function; };
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template <> struct seeded_hash<std::hash<cxxmph::StringPiece> >
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{ typedef seeded_hash_function<Murmur2StringPiece> hash_function; };
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template <> struct seeded_hash<std::hash<char> >
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{ typedef seeded_hash_function<Murmur2> hash_function; };
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template <> struct seeded_hash<std::hash<unsigned char> >
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{ typedef seeded_hash_function<Murmur2> hash_function; };
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template <> struct seeded_hash<std::hash<short> >
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{ typedef seeded_hash_function<Murmur2> hash_function; };
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template <> struct seeded_hash<std::hash<unsigned short> >
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{ typedef seeded_hash_function<Murmur2> hash_function; };
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template <> struct seeded_hash<std::hash<int> >
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{ typedef seeded_hash_function<Murmur2> hash_function; };
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template <> struct seeded_hash<std::hash<unsigned int> >
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{ typedef seeded_hash_function<Murmur2> hash_function; };
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template <> struct seeded_hash<std::hash<long> >
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{ typedef seeded_hash_function<Murmur2> hash_function; };
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template <> struct seeded_hash<std::hash<unsigned long> >
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{ typedef seeded_hash_function<Murmur2> hash_function; };
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template <> struct seeded_hash<std::hash<long long> >
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{ typedef seeded_hash_function<Murmur2> hash_function; };
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template <> struct seeded_hash<std::hash<unsigned long long> >
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{ typedef seeded_hash_function<Murmur2> hash_function; };
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} // namespace cxxmph
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#endif // __CXXMPH_SEEDED_HASH_H__
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