查找字符串的哈希方法
查找字符串的哈希方法
比较经典的字符串hash，相信很多使用C的都使用过了吧。
转贴同学redor的一篇文章，感觉很有用。
// RS Hash Functionunsigned int RSHash( char * str){ unsigned int b = 378551 ; unsigned int a = 63689 ; unsigned int hash = 0 ; while ( * str) { hash = hash * a + ( * str ++ ); a *= b; } return (hash & 0x7FFFFFFF );}// JS Hash Functionunsigned int JSHash( char * str){ unsigned int hash = 1315423911 ; while ( * str) { hash ^= ((hash << 5 ) + ( * str ++ ) + (hash >> 2 )); } return (hash & 0x7FFFFFFF );}// P. J. Weinberger Hash Functionunsigned int PJWHash( char * str){ unsigned int BitsInUnignedInt = (unsigned int )( sizeof (unsigned int ) *8 ); unsigned int ThreeQuarters = (unsigned int )((BitsInUnignedInt * 3 ) / 4 ); unsigned int OneEighth = (unsigned int )(BitsInUnignedInt / 8 ); unsigned int HighBits = (unsigned int )( 0xFFFFFFFF ) << (BitsInUnignedInt - OneEighth); unsigned int hash = 0 ; unsigned int test = 0 ; while ( * str) { hash = (hash << OneEighth) + ( * str ++ ); if ((test = hash & HighBits) != 0 ) { hash = ((hash ^ (test >> ThreeQuarters)) & ( ~ HighBits)); } } return (hash & 0x7FFFFFFF );}// ELF Hash Functionunsigned int ELFHash( char * str){ unsigned int hash = 0 ; unsigned int x = 0 ; while ( * str) { hash = (hash << 4 ) + ( * str ++ ); if ((x = hash & 0xF0000000L ) != 0 ) { hash ^= (x >> 24 ); hash &= ~ x; } } return (hash & 0x7FFFFFFF );}// BKDR Hash Functionunsigned int BKDRHash( char * str){ unsigned int seed = 131 ; // 31 131 1313 13131 131313 etc.. unsigned int hash = 0 ; while ( * str) { hash = hash * seed + ( * str ++ ); } return (hash & 0x7FFFFFFF );}// SDBM Hash Functionunsigned int SDBMHash( char * str){ unsigned int hash = 0 ; while ( * str) { hash = ( * str ++ ) + (hash << 6 ) + (hash << 16 ) - hash; } return (hash & 0x7FFFFFFF );}// DJB Hash Functionunsigned int DJBHash( char * str){ unsigned int hash = 5381 ; while ( * str) { hash += (hash << 5 ) + ( * str ++ ); } return (hash & 0x7FFFFFFF );}// AP Hash Functionunsigned int APHash( char * str){ unsigned int hash = 0 ; int i; for (i = 0 ; * str; i ++ ) { if ((i & 1 ) == 0 ) { hash ^= ((hash << 7 ) ^ ( * str ++ ) ^ (hash >> 3 )); } else { hash ^= ( ~ ((hash << 11 ) ^ ( * str ++ ) ^ (hash >> 5 ))); } } return (hash & 0x7FFFFFFF );}