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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 */
}
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