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 }                    

 

和KMP一样，在查询小串的时候都不如优化过的库函数strstr。