ff_hash.c

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/*****************************************************************************
 *  FullFAT - High Performance, Thread-Safe Embedded FAT File-System         *
 *  Copyright (C) 2009  James Walmsley (james@worm.me.uk)                    *
 *                                                                           *
 *  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     *
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 *  (at your option) any later version.                                      *
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 *  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.                             *
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 *  You should have received a copy of the GNU General Public License        *
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 *  IMPORTANT NOTICE:                                                        *
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 *  Alternative Licensing is available directly from the Copyright holder,   *
 *  (James Walmsley). For more information consult LICENSING.TXT to obtain   *
 *  a Commercial license.                                                    *
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 *****************************************************************************
 *  See http://worm.me.uk/fullfat for more information.                      *
 *  Or  http://fullfat.googlecode.com/ for latest releases and the wiki.     *
 *****************************************************************************/

#include "ff_hash.h"
#include <stdlib.h>
#include <string.h>

#ifdef FF_HASH_CACHE
struct _FF_HASH_TABLE {
    FF_T_UINT8 bitTable[FF_HASH_TABLE_SIZE];
};

FF_HASH_TABLE FF_CreateHashTable() {
    FF_HASH_TABLE pHash = (FF_HASH_TABLE) FF_MALLOC(sizeof(struct _FF_HASH_TABLE));

    if(pHash) {
        FF_ClearHashTable(pHash);
        return pHash;
    }

    return NULL;
}

FF_ERROR FF_ClearHashTable(FF_HASH_TABLE pHash) {
    if(pHash) {
        memset(pHash->bitTable, 0, FF_HASH_TABLE_SIZE);
        return FF_ERR_NONE;
    }

    return FF_ERR_NULL_POINTER;
}

FF_ERROR FF_SetHash(FF_HASH_TABLE pHash, FF_T_UINT32 nHash) {
    FF_T_UINT32 tblIndex    = ((nHash / 8) % FF_HASH_TABLE_SIZE);
    FF_T_UINT32 tblBit      = nHash % 8;

    if(pHash) {
        pHash->bitTable[tblIndex] |= (0x80 >> tblBit);
        return FF_ERR_NONE;
    }

    return FF_ERR_NULL_POINTER; 
}

FF_ERROR FF_ClearHash(FF_HASH_TABLE pHash, FF_T_UINT32 nHash) {
    FF_T_UINT32 tblIndex    = ((nHash / 8) % FF_HASH_TABLE_SIZE);
    FF_T_UINT32 tblBit      = nHash % 8;

    if(pHash) {
        pHash->bitTable[tblIndex] &= ~(0x80 >> tblBit);
        return FF_ERR_NONE;
    }

    return FF_ERR_NULL_POINTER;
}

FF_T_BOOL FF_isHashSet(FF_HASH_TABLE pHash, FF_T_UINT32 nHash) {
    FF_T_UINT32 tblIndex    = ((nHash / 8) % FF_HASH_TABLE_SIZE);
    FF_T_UINT32 tblBit      = nHash % 8;

    if(pHash) {
        if(pHash->bitTable[tblIndex] & (0x80 >> tblBit)) {
            return FF_TRUE;
        }
    }
    return FF_FALSE;
}

FF_ERROR FF_DestroyHashTable(FF_HASH_TABLE pHash) {
    if(pHash) {
        FF_FREE(pHash);
        return FF_ERR_NONE;
    }
    return FF_ERR_NULL_POINTER;
}

#endif