C/C++实现strcpy,strcat,strlen,strcmp标准实现代码

网上很容易找的到,拿出来记录下来备忘:)

char * strcpy (char * dst, char * src)
{
char * cp = dst;

while( *cp++ = *src++ )
; /* Copy src over dst */
return( dst );
}

char * strcat (char * dst, char * src)
{
char * cp = dst;

while( *cp )
++cp; /* Find end of dst */
while( *cp++ = *src++ )
; /* Copy src to end of dst */
return( dst );

}

int strlen (const char * str)
{
int length = 0;

while( *str++ )
++length;

return( length );
}

int strcmp (unsigned char *src, unsigned char *dst)
{
int ret = 0 ;

while( ! (ret = *src - *dst) && *dst)
++src, ++dst;

if ( ret < 0 )
ret = -1 ;
else if ( ret > 0 )
ret = 1 ;

return( ret );
}