字符串操作函数 strstr 实现

<pre name="code" class="cpp"> /* The strstr() function finds the first occurrence of the substring needle in the string haystack. The terminating '\0' characters are not compared. */ char *strstr_r(char *s1, char *s2) { /* s1 : hellwoleddlfjwo, s2: wol */ const char *p1, *p2; if((*s2) == '\0') /* Early versions of Linux libc,strstr would not allow an empty needle argument */ return s1; while( (s1 = strchr(s1, *s2)) != NULL) { p1 = s1; /* found first character of s2, see if the rest matches */ p2 = s2; while((*p1++ == *p2++)) { if(*p1 == '\0') return s1; /* both strings ended together */ } if(*p2 == '\0') { break; } s1++; } return s1; } </pre>