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////////////////////////////////////////////////////////////////////////////////
//
// HashKey.hh
// produced: 01/09/97 jr
// last change: 24/01/99 jr
//
////////////////////////////////////////////////////////////////////////////////
#ifndef HASHKEY_HH
#define HASHKEY_HH
#include "Global.hh"
#include "Field.hh"
namespace topcom {
template<class Key>
class HashKeySize {
public:
inline size_type operator()(const Key& key) const { return key.keysize(); }
};
template<class Key>
class HashKey {
public:
inline size_type operator()(const Key& key, const size_type n) const { return key.key(n); }
};
// for the use in STL vectors/unordered sets/maps:
template<class Key>
class Hash {
private:
static const size_type _init_constant = sizeof(size_type) >= 8 ? 525201411107845655ull : 3323198485ul;
static const size_type _mult_constant = sizeof(size_type) >= 8 ? 0x5bd1e9955bd1e995 : 0x5bd1e995 ;
static const int _shift_constant = sizeof(size_type) >= 8 ? 47ul : 15;
public:
inline size_type operator()(const Key& key) const {
// use single-byte MurmurHash:
size_type result(_init_constant);
const size_type keysize = key.keysize();
for (size_type i = 0; i < keysize; ++i) {
// result = (result << 5) - result;
// result += key.key(i);
result ^= key.key(i);
result *= _mult_constant;
result ^= (result >> _shift_constant);
}
return result;
}
};
template<>
class Hash<size_type> {
public:
inline size_type operator()(const size_type key) const {
return key;
}
};
template<>
class Hash<int> {
public:
inline size_type operator()(const int key) const {
return key;
}
};
//////////////////////////////////////////////////////////////////////////////
// some specializations:
//////////////////////////////////////////////////////////////////////////////
// size_type:
template<>
class HashKeySize<size_type> {
public:
size_type operator()(const size_type& key) const { return 1; }
};
template<>
class HashKey<size_type> {
public:
size_type operator()(const size_type& key, const size_type n) const { return key; }
};
template<>
class HashKeySize<Field> {
public:
inline size_type operator()(const Field& key) const { return 1; }
};
// Field:
template<>
class HashKey<Field> {
public:
inline size_type operator()(const Field& key, const size_type n) const {
hash<Field> hash_obj;
return hash_obj(key);
}
};
}; // namespace topcom
#endif
// eof HashKey.hh
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