字符串函数汇总

char* strcpy(char *strDes, char *strSrc)
{
    if (strDes == strSrc)                       //判断是否相等
        return strDes;
    assert(strDes != NULL && strSrc != NULL);   //判空
    char *des = strDes;                         //保存strDes基址
    while ((*des++ = *strSrc++) != ‘\0‘)       //判断结束
        ;
    return strDes;
}

char* strncpy(char *strDes, char *strSrc, size_t n)
{
    if (strDes == strSrc)
        return strDes;
    assert(n > 0 && strDes != NULL && strSrc != NULL);
    char *des = strDes;
    while ((*des++ = *strSrc++) != ‘\0‘ && n-- > 0)
        ;
    if (*(--des) != ‘\0‘)
        *des = ‘\0‘;
    return strDes;
}

void* memcpy(void* dest, void* source, size_t count)

      {

           void* ret = dest;

          //copy from lower address to higher address

          while (count--)

                  *dest++ = *source;


           return ret;

      }