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/*

FUNCTION

        <<strcmp>>---character string compare

INDEX

        strcmp

ANSI_SYNOPSIS

        #include <string.h>

        int strcmp(const char *<[a]>, const char *<[b]>);

TRAD_SYNOPSIS

        #include <string.h>

        int strcmp(<[a]>, <[b]>)

        char *<[a]>;

        char *<[b]>;

DESCRIPTION

        <<strcmp>> compares the string at <[a]> to

        the string at <[b]>.

RETURNS

        If <<*<[a]>>> sorts lexicographically after <<*<[b]>>>,

        <<strcmp>> returns a number greater than zero.  If the two

        strings match, <<strcmp>> returns zero.  If <<*<[a]>>>

        sorts lexicographically before <<*<[b]>>>, <<strcmp>> returns a

        number less than zero.

PORTABILITY

<<strcmp>> is ANSI C.

<<strcmp>> requires no supporting OS subroutines.

QUICKREF

        strcmp ansi pure

*/

#include <string.h>

#include <limits.h>

/* Nonzero if either X or Y is not aligned on a "long" boundary.  */

#define UNALIGNED(X, Y) \

  (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))

/* DETECTNULL returns nonzero if (long)X contains a NULL byte. */

#if LONG_MAX == 2147483647L

#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)

#else

#if LONG_MAX == 9223372036854775807L

#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)

#else

#error long int is not a 32bit or 64bit type.

#endif

#endif

#ifndef DETECTNULL

#error long int is not a 32bit or 64bit byte

#endif

int

_DEFUN (strcmp, (s1, s2),

        _CONST char *s1 _AND

        _CONST char *s2)

{

#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)

  while (*s1 != '\0' && *s1 == *s2)

    {

      s1++;

      s2++;

    }

  return (*(unsigned char *) s1) - (*(unsigned char *) s2);

#else

  unsigned long *a1;

  unsigned long *a2;

  /* If s1 or s2 are unaligned, then compare bytes. */

  if (!UNALIGNED (s1, s2))

    {

      /* If s1 and s2 are word-aligned, compare them a word at a time. */

      a1 = (unsigned long*)s1;

      a2 = (unsigned long*)s2;

      while (*a1 == *a2)

        {

          /* To get here, *a1 == *a2, thus if we find a null in *a1,

             then the strings must be equal, so return zero.  */

          if (DETECTNULL (*a1))

            return 0;

          a1++;

          a2++;

        }

      /* A difference was detected in last few bytes of s1, so search bytewise */

      s1 = (char*)a1;

      s2 = (char*)a2;

    }

  while (*s1 != '\0' && *s1 == *s2)

    {

      s1++;

      s2++;

    }

  return (*(unsigned char *) s1) - (*(unsigned char *) s2);

#endif /* not PREFER_SIZE_OVER_SPEED */

}