几个Hash算法

最新推荐文章于 2025-05-05 12:11:34 发布

原创最新推荐文章于 2025-05-05 12:11:34 发布 · 821 阅读

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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
}

}