HashIndex.cpp

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/*
===========================================================================

Doom 3 GPL Source Code
Copyright (C) 1999-2011 id Software LLC, a ZeniMax Media company. 

This file is part of the Doom 3 GPL Source Code (?Doom 3 Source Code?).  

Doom 3 Source Code 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 3 of the License, or
(at your option) any later version.

Doom 3 Source Code 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 Doom 3 Source Code.  If not, see <http://www.gnu.org/licenses/>.

In addition, the Doom 3 Source Code is also subject to certain additional terms. You should have received a copy of these additional terms immediately following the terms and conditions of the GNU General Public License which accompanied the Doom 3 Source Code.  If not, please request a copy in writing from id Software at the address below.

If you have questions concerning this license or the applicable additional terms, you may contact in writing id Software LLC, c/o ZeniMax Media Inc., Suite 120, Rockville, Maryland 20850 USA.

===========================================================================
*/

#include "../precompiled.h"
#pragma hdrstop

int idHashIndex::INVALID_INDEX[1] = { -1 };

/*
================
idHashIndex::Init
================
*/
void idHashIndex::Init( const int initialHashSize, const int initialIndexSize ) {
        assert( idMath::IsPowerOfTwo( initialHashSize ) );

        hashSize = initialHashSize;
        hash = INVALID_INDEX;
        indexSize = initialIndexSize;
        indexChain = INVALID_INDEX;
        granularity = DEFAULT_HASH_GRANULARITY;
        hashMask = hashSize - 1;
        lookupMask = 0;
}

/*
================
idHashIndex::Allocate
================
*/
void idHashIndex::Allocate( const int newHashSize, const int newIndexSize ) {
        assert( idMath::IsPowerOfTwo( newHashSize ) );

        Free();
        hashSize = newHashSize;
        hash = new int[hashSize];
        memset( hash, 0xff, hashSize * sizeof( hash[0] ) );
        indexSize = newIndexSize;
        indexChain = new int[indexSize];
        memset( indexChain, 0xff, indexSize * sizeof( indexChain[0] ) );
        hashMask = hashSize - 1;
        lookupMask = -1;
}

/*
================
idHashIndex::Free
================
*/
void idHashIndex::Free( void ) {
        if ( hash != INVALID_INDEX ) {
                delete[] hash;
                hash = INVALID_INDEX;
        }
        if ( indexChain != INVALID_INDEX ) {
                delete[] indexChain;
                indexChain = INVALID_INDEX;
        }
        lookupMask = 0;
}

/*
================
idHashIndex::ResizeIndex
================
*/
void idHashIndex::ResizeIndex( const int newIndexSize ) {
        int *oldIndexChain, mod, newSize;

        if ( newIndexSize <= indexSize ) {
                return;
        }

        mod = newIndexSize % granularity;
        if ( !mod ) {
                newSize = newIndexSize;
        } else {
                newSize = newIndexSize + granularity - mod;
        }

        if ( indexChain == INVALID_INDEX ) {
                indexSize = newSize;
                return;
        }

        oldIndexChain = indexChain;
        indexChain = new int[newSize];
        memcpy( indexChain, oldIndexChain, indexSize * sizeof(int) );
        memset( indexChain + indexSize, 0xff, (newSize - indexSize) * sizeof(int) );
        delete[] oldIndexChain;
        indexSize = newSize;
}

/*
================
idHashIndex::GetSpread
================
*/
int idHashIndex::GetSpread( void ) const {
        int i, index, totalItems, *numHashItems, average, error, e;

        if ( hash == INVALID_INDEX ) {
                return 100;
        }

        totalItems = 0;
        numHashItems = new int[hashSize];
        for ( i = 0; i < hashSize; i++ ) {
                numHashItems[i] = 0;
                for ( index = hash[i]; index >= 0; index = indexChain[index] ) {
                        numHashItems[i]++;
                }
                totalItems += numHashItems[i];
        }
        // if no items in hash
        if ( totalItems <= 1 ) {
                delete[] numHashItems;
                return 100;
        }
        average = totalItems / hashSize;
        error = 0;
        for ( i = 0; i < hashSize; i++ ) {
                e = abs( numHashItems[i] - average );
                if ( e > 1 ) {
                        error += e - 1;
                }
        }
        delete[] numHashItems;
        return 100 - (error * 100 / totalItems);
}