Sunday串匹配算法 C语言实现

 1 unsigned char * sunday( void * a_buf1,
 2                         unsigned int len1,
 3                         void * a_buf2,
 4                         unsigned int len2 ){
 5 
 6     unsigned char * buf1 = ( unsigned char * )a_buf1;
 7     unsigned char * buf2 = ( unsigned char * )a_buf2;
 8 
 9     unsigned int next[256];
10     unsigned int i, j, pos;
11 
12 
13     for( i = 0; i < 256; ++i ){
14 
15         next[i] = len2 + 1;
16     }
17 
18     for( i = 0; i < len2; ++i ){
19 
20         next[buf2[i]] = len2 - i;
21     }
22 
23 
24     pos = 0;
25 
26     while( pos < len1 - len2 + 1 ){
27 
28         i = pos;
29         j = 0;
30 
31         while( j < len2 ){
32 
33             if( buf1[i] != buf2[j] ){
34 
35                 pos += next[buf1[pos + len2]];
36                 break;
37             }
38 
39             ++i;
40             ++j;
41         }
42 
43         if( j == len2 ){
44 
45             return &buf1[pos];
46         }
47     }
48 
49 
50     return NULL;
51 }