C语言字符串长度和字符串复制实现

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

//字符串的长度
int mystrlen(const char* str)
{
if (str == NULL)
return -1;
int len = 0;
while (*str++ != '\0')
{
len++;
}

return len;
}

//从strSrc复制到strDest
//其中strDest长度要大于strSrc的长度
char* mystrcpy(char* strDest, const char* strSrc)
{
if (strDest == NULL || strSrc == NULL)
return NULL;
if (strDest == strSrc)
return strDest;
char* tmp = strDest;
while ((*strDest++ = *strSrc++) != '\0');

return tmp;
}

int main()
{
char* q = "abcdefg";
//strcpy_s(q,sizeof("123456"), "123456");
printf("%d\n", mystrlen(q));
printf("%d\n", strlen(q));

//printf("%s\n", q);

return 0;
}