coco
81 lines
2.3 KiB
C++
81 lines
2.3 KiB
C++
// Copyright (C) 2003 Davis E. King (davis@dlib.net)
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// License: Boost Software License See LICENSE.txt for the full license.
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#ifndef DLIB_GENERAL_HASh_
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#define DLIB_GENERAL_HASh_
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#include <string>
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#include "hash.h"
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namespace dlib
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{
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// ----------------------------------------------------------------------------------------
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// ----------------------------------------------------------------------------------------
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// ----------------------- provide a general hashing function object ----------------------
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// ----------------------------------------------------------------------------------------
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// ----------------------------------------------------------------------------------------
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template <
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typename T
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>
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class general_hash
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{
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public:
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inline unsigned long operator() (
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const T& item
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) const;
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};
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/*!
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Note that the default behavior of general hash is to attempt to cast
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an object of type T to an unsigned long and use that as the hash.
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REQUIREMENTS ON general_hash
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- must have a default constructor
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- must be a function object which overloads operator() as follows:
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unsigned long operator()(const T& item)
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- must take item, compute a hash number and return it
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- must not throw
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- must define the hash in such a way that all equivalent objects have
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the same hash. where equivalent means the following:
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definition of equivalent:
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a is equivalent to b if
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a < b == false and
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b < a == false
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!*/
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// ---------------
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template <
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typename T
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>
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unsigned long general_hash<T>::
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operator() (
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const T& item
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) const
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{
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// hash any types that have a conversion to uint64
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return hash(static_cast<uint64>(item));
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}
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// ---------------
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// std::string hash
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template <>
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inline unsigned long general_hash<std::string>::
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operator() (
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const std::string& item
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) const
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{
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return hash(item);
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}
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// ----------------------------------------------------------------------------------------
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// ----------------------------------------------------------------------------------------
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}
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#endif // DLIB_GENERAL_HASh_
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