几个Hash算法

1

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unsigned long getHashIndex( const char *key, int nTableLength )
{
unsigned long nHash = 0;

while (*key)
{
nHash = (nHash<<5) + nHash + *key++;
}

return ( nHash % nTableLength );
}

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2、据说不错的字符串hash算法，来自lua，有空或者机会值得一试
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unsigned long hash(const char *name,size_t len)
{
    unsigned long h=(unsigned long)len;
    size_t step = (len>>5)+1;
    for(size_t i=len; i>=step; i-=step)
        h = h ^ ((h<<5)+(h>>2)+(unsigned long)name[i-1]);
    return h;
}
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 3，MPQ的hash算法
unsigned long HashString(char *lpszFileName, unsigned long dwHashType)
{
    unsigned char *key = (unsigned char *)lpszFileName;
    unsigned long seed1 = 0x7FED7FED;
 unsigned long seed2 = 0xEEEEEEEE;
    int ch;

    while(*key != 0)
    {
        ch = toupper(*key++);

        seed1 = cryptTable[(dwHashType << 8) + ch] ^ (seed1 + seed2);
        seed2 = ch + seed1 + seed2 + (seed2 << 5) + 3;
    }
    return seed1;

对应的MPQ定位文件名的方法：

int GetHashTablePos(char *lpszString, MPQHASHTABLE *lpTable, int nTableSize)
{
    const int HASH_OFFSET = 0, HASH_A = 1, HASH_B = 2;
    int nHash = HashString(lpszString, HASH_OFFSET),
        nHashA = HashString(lpszString, HASH_A),
        nHashB = HashString(lpszString, HASH_B),
        nHashStart = nHash % nTableSize,
        nHashPos = nHashStart;
    while (lpTable[nHashPos].bExists)
    {
        if (lpTable[nHashPos].nHashA == nHashA && lpTable[nHashPos].nHashB == nHashB)
            return nHashPos;
        else
            nHashPos = (nHashPos + 1) % nTableSize;

        if (nHashPos == nHashStart)
            break;
    }
    return -1; //Error value
}

}