firmware/libc/strcmp.c

   1 /*
   2 FUNCTION
   3         <<strcmp>>---character string compare
   4
   5 INDEX
   6         strcmp
   7
   8 ANSI_SYNOPSIS
   9         #include <string.h>
  10         int strcmp(const char *<[a]>, const char *<[b]>);
  11
  12 TRAD_SYNOPSIS
  13         #include <string.h>
  14         int strcmp(<[a]>, <[b]>)
  15         char *<[a]>;
  16         char *<[b]>;
  17
  18 DESCRIPTION
  19         <<strcmp>> compares the string at <[a]> to
  20         the string at <[b]>.
  21
  22 RETURNS
  23         If <<*<[a]>>> sorts lexicographically after <<*<[b]>>>,
  24         <<strcmp>> returns a number greater than zero.  If the two
  25         strings match, <<strcmp>> returns zero.  If <<*<[a]>>>
  26         sorts lexicographically before <<*<[b]>>>, <<strcmp>> returns a
  27         number less than zero.
  28
  29 PORTABILITY
  30 <<strcmp>> is ANSI C.
  31
  32 <<strcmp>> requires no supporting OS subroutines.
  33
  34 QUICKREF
  35         strcmp ansi pure
  36 */
  37
  38 #include <string.h>
  39 #include <limits.h>
  40
  41 /* Nonzero if either X or Y is not aligned on a "long" boundary.  */
  42 #define UNALIGNED(X, Y) \
  43   (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
  44
  45 /* DETECTNULL returns nonzero if (long)X contains a NULL byte. */
  46 #if LONG_MAX == 2147483647L
  47 #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
  48 #else
  49 #if LONG_MAX == 9223372036854775807L
  50 #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
  51 #else
  52 #error long int is not a 32bit or 64bit type.
  53 #endif
  54 #endif
  55
  56 #ifndef DETECTNULL
  57 #error long int is not a 32bit or 64bit byte
  58 #endif
  59
  60 int
  61 _DEFUN (strcmp, (s1, s2),
  62         _CONST char *s1 _AND
  63         _CONST char *s2)
  64 {
  65 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
  66   while (*s1 != '\0' && *s1 == *s2)
  67     {
  68       s1++;
  69       s2++;
  70     }
  71
  72   return (*(unsigned char *) s1) - (*(unsigned char *) s2);
  73 #else
  74   unsigned long *a1;
  75   unsigned long *a2;
  76
  77   /* If s1 or s2 are unaligned, then compare bytes. */
  78   if (!UNALIGNED (s1, s2))
  79     {
  80       /* If s1 and s2 are word-aligned, compare them a word at a time. */
  81       a1 = (unsigned long*)s1;
  82       a2 = (unsigned long*)s2;
  83       while (*a1 == *a2)
  84         {
  85           /* To get here, *a1 == *a2, thus if we find a null in *a1,
  86              then the strings must be equal, so return zero.  */
  87           if (DETECTNULL (*a1))
  88             return 0;
  89
  90           a1++;
  91           a2++;
  92         }
  93
  94       /* A difference was detected in last few bytes of s1, so search bytewise */
  95       s1 = (char*)a1;
  96       s2 = (char*)a2;
  97     }
  98
  99   while (*s1 != '\0' && *s1 == *s2)
 100     {
 101       s1++;
 102       s2++;
 103     }
 104   return (*(unsigned char *) s1) - (*(unsigned char *) s2);
 105 #endif /* not PREFER_SIZE_OVER_SPEED */
 106 }