C字符串操作函数实现

下面是部分C字符串操作函数的实现，或许在某些笔试时可以用到！

#ifndef NULL #define NULL ((void *)0) #endif /* memcpy的实现代码 */ void* memcpy(void *pDst, void *pSrc, int iLen) { char *pTmp = (char *)pDst; char *pTmp2 = (char *)pSrc; if(0 == iLen) return pDst; while(iLen--) *pTmp++ = *pTmp2++; return pDst; } /* memset的实现代码 */ void* memset(void *pDst, int iSet, int iLen) { char *pTmp = (char *)pDst; if(0 == iLen) return pDst; while(iLen--) *pTmp++ = (char)iSet; return pDst; } /* strcpy的实现代码 */ char *strcpy(char *pDst, char *pSrc) { char *pRst = pDst; do *pDst++ = *pSrc; while(*pSrc++); return pRst; } /* strcat的实现代码 */ char *strcat(char *s, char *a) { char *save = s; for(; *s; ++s); while((*s++ = *a++) != 0); return save; } /* strlen的实现代码 */ int strlen(char *pStr) { int iLen = 0; while(*pStr++) iLen++; return iLen; } /* strcmp的实现 */ int strcmp(char *s, char *t) { for(; *s == *t; s++, t++) { if(('/0' == *s) || ('/0' == *t)) { if(*s == *t) return 0; else break; } } return ((*s > *t) ? 1 : -1); } /* strncmp的实现 */ int m_strncmp(char *s, char *t, int n) { if(0 == n) return 0; for (; (--n > 0) && (*s==*t); s++,t++) { if ('/0'==*s) return 0; } if(*s == *t) return 0; return ((*s > *t) ? 1 : -1); } /* strstr的实现 */ char* strstr(char *s, char *find) { char c, sc; unsigned int len; if ((c = *find++) != 0) { len = lzs_strlen(find); do { do { if ((sc = *s++) == 0) return (NULL); } while (sc != c); } while (lzs_strncmp(s, find, len) != 0); s--; } return ((char *)s); }