/usr/include/tulip/tuliphash.h is in libtulip-dev 4.6.0dfsg-2+b5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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*
* This file is part of Tulip (www.tulip-software.org)
*
* Authors: David Auber and the Tulip development Team
* from LaBRI, University of Bordeaux
*
* Tulip is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation, either version 3
* of the License, or (at your option) any later version.
*
* Tulip 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.
*
*/
///@cond DOXYGEN_HIDDEN
#ifndef TLP_HASH_H
#define TLP_HASH_H
// to search for _LIBCPP_VERSION
#include <ciso646>
/**
* @brief This file defines what class is used to provide a hashmap.
* The TLP_HASH_MAP macro defines which implementation is used for hash maps.
* The TLP_HASH_SET macro defines which implementation is used for hash sets.
*
* TLP_BEGIN_HASH_NAMESPACE is defined to open the namespace in which the hash classes are defined, to define new hashes (e.g. for Edge).
* TLP_END_HASH_NAMESPACE is definde to close the namespace (only used when using std::tr1)
* TLP_HASH_NAMESPACE allows to use a specific hasher class when declaring a hash set or a hash map.
*/
//VS2010 and later can use C++0x's unordered_map; vs2008 uses boost's tr1 implementation
#if defined(_MSC_VER) && (_MSC_VER > 1500)
# define TLP_USE_UNORDERED_MAP
#elif defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L || defined(_LIBCPP_VERSION)
# define TLP_USE_UNORDERED_MAP
#endif
#ifdef TLP_USE_UNORDERED_MAP
# include <unordered_map>
# include <unordered_set>
# define TLP_HASH_MAP std::unordered_map
# define TLP_HASH_SET std::unordered_set
# define TLP_HASH_NAMESPACE std
# define TLP_BEGIN_HASH_NAMESPACE namespace std
# define TLP_END_HASH_NAMESPACE
//clang, and GCC versions prior to the 4.x series do not have tr1; using ext
#elif (! defined _MSC_VER && (__GNUC__ < 4 || __GNUC_MINOR__ < 1))
# include <tulip/tulipconf.h>
# if (__GNUC__ < 3)
# include <hash_map>
# include <hash_set>
# else
# include <ext/hash_map>
# include <ext/hash_set>
# endif
# define TLP_HASH_MAP stdext::hash_map
# define TLP_HASH_SET stdext::hash_set
# define TLP_HASH_NAMESPACE stdext
# define TLP_BEGIN_HASH_NAMESPACE namespace stdext
# define TLP_END_HASH_NAMESPACE
# include <string>
namespace stdext {
template<> struct hash<const std::string> {
size_t operator()(const std::string &s) const {
return hash<const char *>()(s.c_str());
}
};
template<> struct hash<std::string> {
size_t operator()(const std::string &s) const {
return hash<const char *>()(s.c_str());
}
};
template<>
struct hash<double> {
size_t operator()(const double s) const {
return (size_t) s;
}
};
template<>
struct hash<float> {
size_t operator()(const float s) const {
return hash<unsigned int>()(*((unsigned int *) &s));
}
};
}
//MSVC < 2010 use tr1 from boost, and GCC 4.X provides tr1 too.
#else
# include <tr1/unordered_map>
# include <tr1/unordered_set>
# define TLP_HASH_MAP std::tr1::unordered_map
# define TLP_HASH_SET std::tr1::unordered_set
# define TLP_HASH_NAMESPACE std::tr1
# define TLP_BEGIN_HASH_NAMESPACE namespace std { namespace tr1
# define TLP_END_HASH_NAMESPACE }
#endif
// The hash_combine function from the boost library
// Call it repeatedly to incrementally create a hash value from several variables.
// Explanation of the formula from StackOverflow (http://stackoverflow.com/questions/4948780/magic-numbers-in-boosthash-combine) :
// The magic number 0x9e3779b9 = 2^32 / ((1 + sqrt(5)) / 2) is the reciprocal of the golden ratio.
// It is supposed to be 32 random bits, where each is equally likely to be 0 or 1, and with no simple correlation between the bits.
// So including this number "randomly" changes each bit of the seed; as you say, this means that consecutive values will be far apart.
// Including the shifted versions of the old seed makes sure that, even if hash_value() has a fairly small range of values,
// differences will soon be spread across all the bits.
TLP_BEGIN_HASH_NAMESPACE {
template <class T>
inline void hash_combine(std::size_t & seed, const T & v) {
hash<T> hasher;
seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
}
} TLP_END_HASH_NAMESPACE
#endif
///@endcond
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