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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef __BLI_HASH_HH__
#define __BLI_HASH_HH__
/** \file
* \ingroup bli
*
* This file provides default hash functions for some primitive types. The hash functions can be
* used by containers such as Map and Set.
*/
#include <functional>
#include <memory>
#include <string>
#include <utility>
#include "BLI_math_base.h"
#include "BLI_string_ref.hh"
#include "BLI_utildefines.h"
namespace BLI {
template<typename T> struct DefaultHash {
};
#define TRIVIAL_DEFAULT_INT_HASH(TYPE) \
template<> struct DefaultHash<TYPE> { \
uint32_t operator()(TYPE value) const \
{ \
return (uint32_t)value; \
} \
}
/**
* Cannot make any assumptions about the distribution of keys, so use a trivial hash function by
* default. The hash table implementations are designed to take all bits of the hash into account
* to avoid really bad behavior when the lower bits are all zero. Special hash functions can be
* implemented when more knowledge about a specific key distribution is available.
*/
TRIVIAL_DEFAULT_INT_HASH(int8_t);
TRIVIAL_DEFAULT_INT_HASH(uint8_t);
TRIVIAL_DEFAULT_INT_HASH(int16_t);
TRIVIAL_DEFAULT_INT_HASH(uint16_t);
TRIVIAL_DEFAULT_INT_HASH(int32_t);
TRIVIAL_DEFAULT_INT_HASH(uint32_t);
TRIVIAL_DEFAULT_INT_HASH(int64_t);
TRIVIAL_DEFAULT_INT_HASH(uint64_t);
template<> struct DefaultHash<float> {
uint32_t operator()(float value) const
{
return *(uint32_t *)&value;
}
};
inline uint32_t hash_string(StringRef str)
{
uint32_t hash = 5381;
for (char c : str) {
hash = hash * 33 + c;
}
return hash;
}
template<> struct DefaultHash<std::string> {
uint32_t operator()(const std::string &value) const
{
return hash_string(value);
}
};
template<> struct DefaultHash<StringRef> {
uint32_t operator()(const StringRef &value) const
{
return hash_string(value);
}
};
template<> struct DefaultHash<StringRefNull> {
uint32_t operator()(const StringRefNull &value) const
{
return hash_string(value);
}
};
/**
* While we cannot guarantee that the lower 3 bits or a pointer are zero, it is safe to assume
* this in the general case. MEM_malloc only returns 8 byte aligned addresses on 64-bit systems.
*/
template<typename T> struct DefaultHash<T *> {
uint32_t operator()(const T *value) const
{
uintptr_t ptr = POINTER_AS_UINT(value);
uint32_t hash = (uint32_t)(ptr >> 3);
return hash;
}
};
template<typename T> struct DefaultHash<std::unique_ptr<T>> {
uint32_t operator()(const std::unique_ptr<T> &value) const
{
return DefaultHash<T *>{}(value.get());
}
};
template<typename T1, typename T2> struct DefaultHash<std::pair<T1, T2>> {
uint32_t operator()(const std::pair<T1, T2> &value) const
{
uint32_t hash1 = DefaultHash<T1>{}(value.first);
uint32_t hash2 = DefaultHash<T2>{}(value.second);
return hash1 ^ (hash2 * 33);
}
};
} // namespace BLI
#endif /* __BLI_HASH_HH__ */
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