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Starting to add examples for using the unordered container library.

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[SVN r3046]
This commit is contained in:
Daniel James
2006-07-02 22:54:20 +00:00
parent ce6b35d9e2
commit ef5dda10a7
1 changed files with 66 additions and 0 deletions
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examples/hash_functions/fnv-1.hpp Normal file
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// See: http://www.isthe.com/chongo/tech/comp/fnv/
#include <string>
namespace hash
{
template <std::size_t FnvPrime, std::size_t OffsetBias>
struct basic_fnv_1
{
std::size_t operator()(std::string const& text)
{
std::size_t hash = OffsetBias;
for(std::string::const_iterator it = text.begin(), end = text.end();
it != end; ++it)
{
hash *= FnvPrime;
hash ^= *it;
}
return hash;
}
};
template <std::size_t FnvPrime, std::size_t OffsetBias>
struct basic_fnv_1a
{
std::size_t operator()(std::string const& text)
{
std::size_t hash = OffsetBias;
for(std::string::const_iterator it = text.begin(), end = text.end();
it != end; ++it)
{
hash ^= *it;
hash *= FnvPrime;
}
return hash;
}
};
// TODO: Select Bias & Prime base on the size of std::size_t.
//
// 32 bit FNV_prime = 16777619
// 64 bit FNV_prime = 1099511628211
// 128 bit FNV_prime = 309485009821345068724781401
// 256 bit FNV_prime = 374144419156711147060143317175368453031918731002211
//
// 32 bit offset_basis = 2166136261
// 64 bit offset_basis = 14695981039346656037
// 128 bit offset_basis = 275519064689413815358837431229664493455
// 256 bit offset_basis = 100029257958052580907070968620625704837092796014241193945225284501741471925557
const std::size_t fnv_prime = 16777619;
// 64 bit FNV_prime = 1099511628211
// 128 bit FNV_prime = 309485009821345068724781401
// 256 bit FNV_prime = 374144419156711147060143317175368453031918731002211
const std::size_t fnv_offset_bias = 2166136261;
// 64 bit offset_basis = 14695981039346656037
// 128 bit offset_basis = 275519064689413815358837431229664493455
// 256 bit offset_basis = 100029257958052580907070968620625704837092796014241193945225284501741471925557
typedef basic_fnv_1<fnv_prime, fnv_offset_bias> fnv_1;
typedef basic_fnv_1a<fnv_prime, fnv_offset_bias> fnv_1a;
}