lib/strverscmp.c

   1 /* Compare strings while treating digits characters numerically.
   2    Copyright (C) 1997, 2000 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Jean-François Bignolles <bignolle@ecoledoc.ibp.fr>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #if HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #include <string.h>
  26 #include <ctype.h>
  27
  28 /* states: S_N: normal, S_I: comparing integral part, S_F: comparing
  29            Fractional parts, S_Z: idem but with leading Zeroes only */
  30 #define S_N    0x0
  31 #define S_I    0x4
  32 #define S_F    0x8
  33 #define S_Z    0xC
  34
  35 /* result_type: CMP: return diff; LEN: compare using len_diff/diff */
  36 #define CMP    2
  37 #define LEN    3
  38
  39 /* ISDIGIT differs from isdigit, as follows:
  40    - Its arg may be any int or unsigned int; it need not be an unsigned char.
  41    - It's guaranteed to evaluate its argument exactly once.
  42    - It's typically faster.
  43    Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 says that
  44    only '0' through '9' are digits.  Prefer ISDIGIT to isdigit unless
  45    it's important to use the locale's definition of `digit' even when the
  46    host does not conform to Posix.  */
  47 #define ISDIGIT(c) ((unsigned) (c) - '0' <= 9)
  48
  49 /* Compare S1 and S2 as strings holding indices/version numbers,
  50    returning less than, equal to or greater than zero if S1 is less than,
  51    equal to or greater than S2 (for more info, see the texinfo doc).
  52 */
  53
  54 int
  55 strverscmp (const char *s1, const char *s2)
  56 {
  57   const unsigned char *p1 = (const unsigned char *) s1;
  58   const unsigned char *p2 = (const unsigned char *) s2;
  59   unsigned char c1, c2;
  60   int state;
  61   int diff;
  62
  63   /* Symbol(s)    0       [1-9]   others  (padding)
  64      Transition   (10) 0  (01) d  (00) x  (11) -   */
  65   static const unsigned int next_state[] =
  66   {
  67       /* state    x    d    0    - */
  68       /* S_N */  S_N, S_I, S_Z, S_N,
  69       /* S_I */  S_N, S_I, S_I, S_I,
  70       /* S_F */  S_N, S_F, S_F, S_F,
  71       /* S_Z */  S_N, S_F, S_Z, S_Z
  72   };
  73
  74   static const int result_type[] =
  75   {
  76       /* state   x/x  x/d  x/0  x/-  d/x  d/d  d/0  d/-
  77                  0/x  0/d  0/0  0/-  -/x  -/d  -/0  -/- */
  78
  79       /* S_N */  CMP, CMP, CMP, CMP, CMP, LEN, CMP, CMP,
  80                  CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
  81       /* S_I */  CMP, -1,  -1,  CMP,  1,  LEN, LEN, CMP,
  82                   1,  LEN, LEN, CMP, CMP, CMP, CMP, CMP,
  83       /* S_F */  CMP, CMP, CMP, CMP, CMP, LEN, CMP, CMP,
  84                  CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
  85       /* S_Z */  CMP,  1,   1,  CMP, -1,  CMP, CMP, CMP,
  86                  -1,  CMP, CMP, CMP
  87   };
  88
  89   if (p1 == p2)
  90     return 0;
  91
  92   c1 = *p1++;
  93   c2 = *p2++;
  94   /* Hint: '0' is a digit too.  */
  95   state = S_N | ((c1 == '0') + (ISDIGIT (c1) != 0));
  96
  97   while ((diff = c1 - c2) == 0 && c1 != '\0')
  98     {
  99       state = next_state[state];
 100       c1 = *p1++;
 101       c2 = *p2++;
 102       state |= (c1 == '0') + (ISDIGIT (c1) != 0);
 103     }
 104
 105   state = result_type[state << 2 | ((c2 == '0') + (ISDIGIT (c2) != 0))];
 106
 107   switch (state)
 108     {
 109     case CMP:
 110       return diff;
 111
 112     case LEN:
 113       while (ISDIGIT (*p1++))
 114         if (!ISDIGIT (*p2++))
 115           return 1;
 116
 117       return ISDIGIT (*p2) ? -1 : diff;
 118
 119     default:
 120       return state;
 121     }
 122 }