81 lines
2.2 KiB
C++
81 lines
2.2 KiB
C++
/******************************************************************************/
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/* HASH INDEX *****************************************************************/
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/******************************************************************************/
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#ifndef _H_EBCL_HASHINDEX
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#define _H_EBCL_HASHINDEX
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#include <ebcl/Externals.hh>
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#include <ebcl/Pointers.hh>
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namespace ebcl {
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/*
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* This is based on http://glampert.com/2016/05-04/dissecting-idhashindex,
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* which explains how the hash tables in idTech4 work. Not looking at the code
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* to avoid GPL-related issues, so my implementation will probably suck.
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*
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* Unlike the original thing, this version considers that:
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* - all additions are made at the end of the array (and therefore at the
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* end of the index),
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* - erasing is done by swapping the element being erased and the last
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* element of the index.
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*
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* It also keeps track of the hash key for a given index in order to make
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* erasing easier.
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*/
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class T_HashIndex
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{
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public:
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static constexpr uint32_t INVALID_INDEX = 0xffffffff;
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static constexpr uint32_t DEFAULT_SIZE = 1024;
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static constexpr uint32_t DEFAULT_GROWTH = 1024;
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private:
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static uint32_t invalidIndex_;
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uint32_t hashSize_;
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uint32_t* hash_;
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uint32_t indexSize_;
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uint32_t indexGrowth_;
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uint32_t indexUsed_;
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uint32_t* index_;
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uint32_t* indexReverse_;
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uint32_t hashMask_;
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uint32_t lookupMask_;
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void enlargeIndex( uint32_t needed );
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void allocateIfNecessary( );
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public:
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T_HashIndex( ) noexcept;
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T_HashIndex( uint32_t hashSize , uint32_t indexSize , uint32_t growth = DEFAULT_GROWTH ) noexcept;
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T_HashIndex( T_HashIndex const& source );
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T_HashIndex( T_HashIndex&& source ) noexcept;
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~T_HashIndex( );
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T_HashIndex& operator =( T_HashIndex const& other );
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T_HashIndex& operator =( T_HashIndex&& other ) noexcept;
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friend void swap( T_HashIndex& lhs , T_HashIndex& rhs ) noexcept;
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void free( );
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void clear( );
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void add( uint32_t key );
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void remove( uint32_t index );
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uint32_t first( uint32_t key ) const;
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uint32_t next( uint32_t index ) const;
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};
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M_CLASS_POINTERS( HashIndex );
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void swap( T_HashIndex& lhs , T_HashIndex& rhs ) noexcept;
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} // namespace
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#include <ebcl/inline/HashIndex.hh>
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#endif // _H_EBCL_HASHINDEX
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