1  /* strncmp -- compare two strings, stop after n bytes.
       2     This function is in the public domain.  */
       3  
       4  /*
       5  
       6  @deftypefn Supplemental int strncmp (const char *@var{s1}, @
       7    const char *@var{s2}, size_t @var{n})
       8  
       9  Compares the first @var{n} bytes of two strings, returning a value as
      10  @code{strcmp}.
      11  
      12  @end deftypefn
      13  
      14  */
      15  
      16  #include <ansidecl.h>
      17  #include <stddef.h>
      18  
      19  int
      20  strncmp(const char *s1, const char *s2, register size_t n)
      21  {
      22    register unsigned char u1, u2;
      23  
      24    while (n-- > 0)
      25      {
      26        u1 = (unsigned char) *s1++;
      27        u2 = (unsigned char) *s2++;
      28        if (u1 != u2)
      29  	return u1 - u2;
      30        if (u1 == '\0')
      31  	return 0;
      32      }
      33    return 0;
      34  }