常用的字符串hash算法（转载） 

  1 // RS Hash Function
  2 unsigned int RSHash(char* str)
  3 {
  4 unsigned int b = 378551 ;
  5 unsigned int a = 63689 ;
  6 unsigned int hash = 0 ;
  7 while (*str)
  8 {
  9 hash = hash * a + (*str ++ );
 10 a *= b;
 11 }
 12 return (hash & 0x7FFFFFFF );
 13 }
 14 
 15 // JS Hash Function
 16 unsigned int JSHash(char* str)
 17 {
 18 unsigned int hash = 1315423911 ;
 19 while (*str)
 20 {
 21 hash ^= ((hash << 5 ) + (*str ++ ) + (hash >> 2 ));
 22 }
 23 return (hash & 0x7FFFFFFF );
 24 }
 25 
 26 // P. J. Weinberger Hash Function
 27 unsigned int PJWHash(char* str)
 28 {
 29 unsigned int BitsInUnignedInt = (unsigned int )( sizeof (unsigned int)*8 );
 30 unsigned int ThreeQuarters = (unsigned int )((BitsInUnignedInt*3 ) / 4 );
 31 unsigned int OneEighth = (unsigned int )(BitsInUnignedInt / 8 );
 32 unsigned int HighBits = (unsigned int )( 0xFFFFFFFF ) << (BitsInUnignedInt - OneEighth);
 33 unsigned int hash = 0 ;
 34 unsigned int test = 0 ;
 35 while (*str)
 36 {
 37 hash = (hash << OneEighth) + (*str ++ );
 38 if ((test = hash & HighBits) != 0 ) {
 39 hash = ((hash ^ (test >> ThreeQuarters)) & ( ~ HighBits));
 40 }
 41 }
 42 return (hash & 0x7FFFFFFF );
 43 }
 44 
 45 // ELF Hash Function
 46 unsigned int ELFHash(char* str)
 47 {
 48 unsigned int hash = 0 ;
 49 unsigned int x = 0 ; while (*str)
 50 {
 51 hash = (hash << 4 ) + (*str ++ );
 52 if ((x = hash & 0xF0000000L ) != 0 ) {
 53 hash ^= (x >> 24 );
 54 hash &= ~ x;
 55 }
 56 }
 57 return (hash & 0x7FFFFFFF );
 58 }
 59 
 60 // BKDR Hash Function
 61 unsigned int BKDRHash(char* str)
 62 {
 63 unsigned int seed = 131 ; // 31 131 1313 13131 131313 etc..
 64 unsigned int hash = 0 ;
 65 while (*str)
 66 {
 67 hash = hash*seed + (*str ++ );
 68 }
 69 return (hash & 0x7FFFFFFF );
 70 }
 71 
 72 // SDBM Hash Function
 73 unsigned int SDBMHash(char* str)
 74 {
 75 unsigned int hash = 0 ;
 76 while (*str)
 77 {
 78 hash = (*str ++ ) + (hash << 6 ) + (hash << 16 ) - hash;
 79 }
 80 return (hash & 0x7FFFFFFF );
 81 }
 82 
 83 // DJB Hash Function
 84 unsigned int DJBHash(char* str)
 85 {
 86 unsigned int hash = 5381 ;
 87 while (*str)
 88 {
 89 hash += (hash << 5 ) + (*str ++ );
 90 }
 91 return (hash & 0x7FFFFFFF );
 92 }
 93 
 94 // AP Hash Function
 95 unsigned int APHash(char* str)
 96 {
 97 unsigned int hash = 0 ;
 98 int i;
 99 for (i = 0 ;*str; i ++ )
100 {
101 if ((i & 1 ) == 0 ) {
102 hash ^= ((hash << 7 ) ^ (*str ++ ) ^ (hash >> 3 ));
103 } else {
104 hash ^= ( ~ ((hash << 11 ) ^ (*str ++ ) ^ (hash >> 5 )));
105 }
106 }
107 return (hash & 0x7FFFFFFF );
108 }
posted @ 2011-05-09 16:04  elwin  阅读(258)  评论(0)    收藏  举报