字节拷贝函数：

void * memcpy1(void *dest, const void *src, size_t n)  {          assert(dest!=NULL&&src!=NULL);    //有效性检测          if(dest == src)                  return dest;          else if(dest < src)          {                  const char *c_src = static_cast<const char *>(src);                  char *c_dest = static_cast<char *>(dest);                  while (n--) *c_dest++ = *c_src++;          }          else          {                  const char *c_src = static_cast<const char *>(src) + n - 1;                  char *c_dest = static_cast<char *>(dest) + n - 1;                  while (n--) *c_dest-- = *c_src--;          }          return dest;  }       

字符串比较函数：

char *strcpy(char *des, const char *src)    {        assert(des != NULL && src != NULL);        char *pStr = des;        while( (*des++ = *src++) != '\0')            NULL;        return pStr;    }        

字符串比较函数：

int  strcmp(const char *des,  const char *src)    {        assert(des != NULL && src != NULL);        for (;*des && *src && *des == *src; des++, src++)            NULL;        return *des - *src;    }        

字符串长度函数：

int strlen(const char *pStr)    {        assert(pStr != NULL);        int len = 0;        while (*pStr++ != '\0')            len++;            return len;    }        

字符串连接函数：

char *strcat(char *des, const char *src)    {        assert(*des != NULL && *src != NULL);        char *pStr = des;        while (*des != '\0')            des++;            while ((*des++ = *src++) != '\0')            NULL;        return pStr;    }     

字符串查找函数：

char *myStrstr(const char *des, const char *src)    {        assert(des != NULL && src != NULL);            char *d = des;        char *s = src;            for (; d != '\0'; des++)        {            for (d = des, s = src; (s != '\0') && (*d == *s); d++, s++)                NULL;                if (*s == '\0')            return des;        }                return NULL;        }