strlen 和 strcmp的源代码

 

 

 

strlen：

int strlen(const char* str)
{
    int i=0;
    while(*str++) i++;
    return i;
}

strcmp：

int strcmp( const char *p1 , const char *p2 )

{

    register const unsigned char *s1 = (const unsigned char *) p1;  

    register const unsigned char *s2 = (const unsigned char *) p2;  

    unsigned char c1, c2;

    do {

        c1 = (unsigned char) *s1++;

        c2 = (unsigned char) *s2++;

        if (c1 == '\0')

             return c1 - c2;

    } while (c1 == c2);

    return c1 - c2;

}