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115 lines
1.9 KiB
C++
115 lines
1.9 KiB
C++
/*
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* Copyright 2010-2013 Branimir Karadzic. All rights reserved.
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* License: http://www.opensource.org/licenses/BSD-2-Clause
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*/
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#ifndef BX_HASH_H_HEADER_GUARD
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#define BX_HASH_H_HEADER_GUARD
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#include "bx.h"
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namespace bx
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{
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// MurmurHash2 was written by Austin Appleby, and is placed in the public
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// domain. The author hereby disclaims copyright to this source code.
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#define MURMUR_M 0x5bd1e995
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#define MURMUR_R 24
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#define mmix(_h, _k) { _k *= MURMUR_M; _k ^= _k >> MURMUR_R; _k *= MURMUR_M; _h *= MURMUR_M; _h ^= _k; }
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class HashMurmur2A
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{
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public:
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void begin(uint32_t _seed = 0)
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{
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m_hash = _seed;
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m_tail = 0;
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m_count = 0;
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m_size = 0;
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}
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void add(const void* _data, int _len)
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{
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const uint8_t* data = (uint8_t*)_data;
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m_size += _len;
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mixTail(data, _len);
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while(_len >= 4)
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{
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uint32_t kk = *(uint32_t*)data;
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mmix(m_hash, kk);
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data += 4;
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_len -= 4;
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}
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mixTail(data, _len);
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}
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template<typename Ty>
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void add(Ty _value)
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{
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add(&_value, sizeof(Ty) );
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}
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uint32_t end()
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{
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mmix(m_hash, m_tail);
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mmix(m_hash, m_size);
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m_hash ^= m_hash >> 13;
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m_hash *= MURMUR_M;
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m_hash ^= m_hash >> 15;
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return m_hash;
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}
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private:
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void mixTail(const uint8_t*& _data, int& _len)
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{
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while( _len && ((_len<4) || m_count) )
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{
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m_tail |= (*_data++) << (m_count * 8);
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m_count++;
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_len--;
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if(m_count == 4)
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{
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mmix(m_hash, m_tail);
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m_tail = 0;
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m_count = 0;
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}
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}
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}
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uint32_t m_hash;
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uint32_t m_tail;
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uint32_t m_count;
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uint32_t m_size;
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};
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#undef MURMUR_M
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#undef MURMUR_R
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#undef mmix
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inline uint32_t hashMurmur2A(const void* _data, uint32_t _size)
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{
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HashMurmur2A murmur;
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murmur.begin();
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murmur.add(_data, (int)_size);
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return murmur.end();
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}
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template <typename Ty>
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inline uint32_t hashMurmur2A(const Ty& _data)
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{
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return hashMurmur2A(&_data, sizeof(Ty) );
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}
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} // namespace bx
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#endif // BX_HASH_H_HEADER_GUARD
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