hash 算法

/* *
* Hash算法大全<br>
* 推薦使用FNV1算法
* @algorithm None
* @author Goodzzp 2006-11-20
* @lastEdit Goodzzp 2006-11-20
* @editDetail Create
*/
public class HashAlgorithms
{
/* *
* 加法hash
* @param key 字符串
* @param prime 一個質數
* @return hash結果
*/
public static int additiveHash(String key, int prime)
{
   int hash, i;
   for (hash = key.length(), i = 0; i < key.length(); i++ )
    hash += key.charAt(i);
   return (hash % prime);
}

/* *
* 旋轉hash
* @param key 輸入字符串
* @param prime 質數
* @return hash值
*/
public static int rotatingHash(String key, int prime)
{
   int hash, i;
   for (hash=key.length(), i=0; i<key.length(); ++ i)
     hash = (hash<<4)^(hash>>28)^ key.charAt(i);
   return (hash % prime);
//   return (hash ^ (hash>>10) ^ (hash>>20));
}

// 替代：
// 使用：hash = (hash ^ (hash>>10) ^ (hash>>20)) & mask;
// 替代：hash %= prime;


/* *
* MASK值，隨便找一個值，最好是質數
*/
static int M_MASK = 0x8765fed1 ;
/* *
* 一次一個hash
* @param key 輸入字符串
* @return 輸出hash值
*/
public static int oneByOneHash(String key)
{
   int    hash, i;
   for (hash=0, i=0; i<key.length(); ++ i)
   {
     hash += key.charAt(i);
     hash += (hash << 10 );
     hash ^= (hash >> 6 );
   }
   hash += (hash << 3 );
   hash ^= (hash >> 11 );
   hash += (hash << 15 );
//   return (hash & M_MASK);
   return hash;
}

/* *
* Bernstein's hash
* @param key 輸入字節數組
* @param level 初始hash常量
* @return 結果hash
*/
public static int bernstein(String key)
{
   int hash = 0 ;
   int i;
   for (i=0; i<key.length(); ++i) hash = 33*hash + key.charAt(i);
   return hash;
}

//
//// Pearson's Hash
// char pearson(char[]key, ub4 len, char tab[256])
// {
//    char hash;
//    ub4 i;
//    for (hash=len, i=0; i<len; ++i)
//      hash=tab[hash^key[i]];
//    return (hash);
// }

//// CRC Hashing，計算crc,具體代碼見其餘
// ub4 crc(char *key, ub4 len, ub4 mask, ub4 tab[256])
// {
//    ub4 hash, i;
//    for (hash=len, i=0; i<len; ++i)
//      hash = (hash >> 8) ^ tab[(hash & 0xff) ^ key[i]];
//    return (hash & mask);
// }

/* *
* Universal Hashing
*/
public static int universal(char[]key, int mask, int [] tab)
{
   int hash = key.length, i, len = key.length;
   for (i=0; i<(len<<3); i+=8 )
   {
     char k = key[i>>3 ];
     if ((k&0x01) == 0) hash ^= tab[i+0 ];
     if ((k&0x02) == 0) hash ^= tab[i+1 ];
     if ((k&0x04) == 0) hash ^= tab[i+2 ];
     if ((k&0x08) == 0) hash ^= tab[i+3 ];
     if ((k&0x10) == 0) hash ^= tab[i+4 ];
     if ((k&0x20) == 0) hash ^= tab[i+5 ];
     if ((k&0x40) == 0) hash ^= tab[i+6 ];
     if ((k&0x80) == 0) hash ^= tab[i+7 ];
   }
   return (hash & mask);
}

/* *
* Zobrist Hashing
*/
public static int zobrist( char[] key,int mask, int [][] tab)
{
   int hash, i;
   for (hash=key.length, i=0; i<key.length; ++ i)
     hash ^= tab[i][key[i]];
   return (hash & mask);
}

// LOOKUP3
// 見Bob Jenkins(3).c文件

// 32位FNV算法
static int M_SHIFT = 0 ;
/* *
* 32位的FNV算法
* @param data 數組
* @return int值
*/
    public static int FNVHash(byte [] data)
    {
        int hash = (int)2166136261L ;
        for(byte b : data)
            hash = (hash * 16777619) ^ b;
        if (M_SHIFT == 0 )
            return hash;
        return (hash ^ (hash >> M_SHIFT)) & M_MASK;
    }
    /* *
     * 改進的32位FNV算法1
     * @param data 數組
     * @return int值
     */
    public static int FNVHash1(byte [] data)
    {
        final int p = 16777619 ;
        int hash = (int)2166136261L ;
        for(byte b:data)
            hash = (hash ^ b) * p;
        hash += hash << 13 ;
        hash ^= hash >> 7 ;
        hash += hash << 3 ;
        hash ^= hash >> 17 ;
        hash += hash << 5 ;
        return hash;
    }
    /* *
     * 改進的32位FNV算法1
     * @param data 字符串
     * @return int值
     */
    public static int FNVHash1(String data)
    {
        final int p = 16777619 ;
        int hash = (int)2166136261L ;
        for(int i=0;i<data.length();i++ )
            hash = (hash ^ data.charAt(i)) * p;
        hash += hash << 13 ;
        hash ^= hash >> 7 ;
        hash += hash << 3 ;
        hash ^= hash >> 17 ;
        hash += hash << 5 ;
        return hash;
    }

    /* *
     * Thomas Wang的算法，整數hash
     */
    public static int intHash(int key)
    {
      key += ~(key << 15 );
      key ^= (key >>> 10 );
      key += (key << 3 );
      key ^= (key >>> 6 );
      key += ~(key << 11 );
      key ^= (key >>> 16 );
      return key;
    }
    /* *
     * RS算法hash
     * @param str 字符串
     */
    public static int RSHash(String str)
    {
        int b    = 378551 ;
        int a    = 63689 ;
        int hash = 0 ;

       for(int i = 0; i < str.length(); i++ )
       {
          hash = hash * a + str.charAt(i);
          a    = a * b;
       }

       return (hash & 0x7FFFFFFF );
    }
    /* End Of RS Hash Function */

    /* *
     * JS算法
     */
    public static int JSHash(String str)
    {
       int hash = 1315423911 ;

       for(int i = 0; i < str.length(); i++ )
       {
          hash ^= ((hash << 5) + str.charAt(i) + (hash >> 2 ));
       }

       return (hash & 0x7FFFFFFF );
    }
    /* End Of JS Hash Function */

    /* *
     * PJW算法
     */
    public static int PJWHash(String str)
    {
        int BitsInUnsignedInt = 32 ;
        int ThreeQuarters     = (BitsInUnsignedInt * 3) / 4 ;
        int OneEighth         = BitsInUnsignedInt / 8 ;
        int HighBits          = 0xFFFFFFFF << (BitsInUnsignedInt - OneEighth);
        int hash              = 0 ;
        int test              = 0 ;

       for(int i = 0; i < str.length();i++ )
       {
          hash = (hash << OneEighth) + str.charAt(i);

          if((test = hash & HighBits) != 0 )
          {
             hash = (( hash ^ (test >> ThreeQuarters)) & (~ HighBits));
          }
       }

       return (hash & 0x7FFFFFFF );
    }
    /* End Of P. J. Weinberger Hash Function */

    /* *
     * ELF算法
     */
    public static int ELFHash(String str)
    {
        int hash = 0 ;
        int x    = 0 ;

       for(int i = 0; i < str.length(); i++ )
       {
          hash = (hash << 4) + str.charAt(i);
          if((x = (int)(hash & 0xF0000000L)) != 0 )
          {
             hash ^= (x >> 24 );
             hash &= ~ x;
          }
       }

       return (hash & 0x7FFFFFFF );
    }
    /* End Of ELF Hash Function */

    /* *
     * BKDR算法
     */
    public static int BKDRHash(String str)
    {
        int seed = 131; // 31 131 1313 13131 131313 etc..
        int hash = 0 ;

       for(int i = 0; i < str.length(); i++ )
       {
          hash = (hash * seed) + str.charAt(i);
       }

       return (hash & 0x7FFFFFFF );
    }
    /* End Of BKDR Hash Function */

    /* *
     * SDBM算法
     */
    public static int SDBMHash(String str)
    {
        int hash = 0 ;

       for(int i = 0; i < str.length(); i++ )
       {
          hash = str.charAt(i) + (hash << 6) + (hash << 16) - hash;
       }

       return (hash & 0x7FFFFFFF );
    }
    /* End Of SDBM Hash Function */

    /* *
     * DJB算法
     */
    public static int DJBHash(String str)
    {
       int hash = 5381 ;

       for(int i = 0; i < str.length(); i++ )
       {
          hash = ((hash << 5) + hash) + str.charAt(i);
       }

       return (hash & 0x7FFFFFFF );
    }
    /* End Of DJB Hash Function */

    /* *
     * DEK算法
     */
    public static int DEKHash(String str)
    {
        int hash = str.length();

       for(int i = 0; i < str.length(); i++ )
       {
          hash = ((hash << 5) ^ (hash >> 27)) ^ str.charAt(i);
       }

       return (hash & 0x7FFFFFFF );
    }
    /* End Of DEK Hash Function */

    /* *
     * AP算法
     */
    public static int APHash(String str)
    {
        int hash = 0 ;

       for(int i = 0; i < str.length(); i++ )
       {
          hash ^= ((i & 1) == 0) ? ( (hash << 7) ^ str.charAt(i) ^ (hash >> 3 )) :
                                   (~((hash << 11) ^ str.charAt(i) ^ (hash >> 5 )));
       }

//       return (hash & 0x7FFFFFFF);
       return hash;
    }
    /* End Of AP Hash Function */
   
    /* *
     * JAVA本身帶的算法
     */
    public static int java(String str)
{
   int h = 0 ;
   int off = 0 ;
   int len = str.length();
   for (int i = 0; i < len; i++ )
   {
    h = 31 * h + str.charAt(off++ );
   }
   return h;
}
   
    /* *
     * 混合hash算法，輸出64位的值
     */
    public static long mixHash(String str)
    {
    long hash = str.hashCode();
    hash <<= 32 ;
    hash |= FNVHash1(str);
    return hash;    }}