strverscmp.c

/* Compare strings while treating digits characters numerically.
   Copyright (C) 1997, 2000, 2002, 2004, 2006, 2009-2015 Free Software
   Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Jean-François Bignolles <bignolle@ecoledoc.ibp.fr>, 1997.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as published by
   the Free Software Foundation; either version 2.1, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License along
   with this program; if not, see <http://www.gnu.org/licenses/>.  */

#if !_LIBC
# include <config.h>
#endif

#include <string.h>
#include <ctype.h>

/* states: S_N: normal, S_I: comparing integral part, S_F: comparing
           fractional parts, S_Z: idem but with leading Zeroes only */
#define S_N    0x0
#define S_I    0x4
#define S_F    0x8
#define S_Z    0xC

/* result_type: CMP: return diff; LEN: compare using len_diff/diff */
#define CMP    2
#define LEN    3


/* ISDIGIT differs from isdigit, as follows:
   - Its arg may be any int or unsigned int; it need not be an unsigned char
     or EOF.
   - It's typically faster.
   POSIX says that only '0' through '9' are digits.  Prefer ISDIGIT to
   isdigit unless it's important to use the locale's definition
   of "digit" even when the host does not conform to POSIX.  */
#define ISDIGIT(c) ((unsigned int) (c) - '0' <= 9)

#undef __strverscmp
#undef strverscmp

#ifndef weak_alias
# define __strverscmp strverscmp
#endif

/* Compare S1 and S2 as strings holding indices/version numbers,
   returning less than, equal to or greater than zero if S1 is less than,
   equal to or greater than S2 (for more info, see the texinfo doc).
*/

int
__strverscmp (const char *s1, const char *s2)
{
  const unsigned char *p1 = (const unsigned char *) s1;
  const unsigned char *p2 = (const unsigned char *) s2;
  unsigned char c1, c2;
  int state;
  int diff;

  /* Symbol(s)    0       [1-9]   others  (padding)
     Transition   (10) 0  (01) d  (00) x  (11) -   */
  static const unsigned int next_state[] =
  {
      /* state    x    d    0    - */
      /* S_N */  S_N, S_I, S_Z, S_N,
      /* S_I */  S_N, S_I, S_I, S_I,
      /* S_F */  S_N, S_F, S_F, S_F,
      /* S_Z */  S_N, S_F, S_Z, S_Z
  };

  static const int result_type[] =
  {
      /* state   x/x  x/d  x/0  x/-  d/x  d/d  d/0  d/-
                 0/x  0/d  0/0  0/-  -/x  -/d  -/0  -/- */

      /* S_N */  CMP, CMP, CMP, CMP, CMP, LEN, CMP, CMP,
                 CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
      /* S_I */  CMP, -1,  -1,  CMP,  1,  LEN, LEN, CMP,
                  1,  LEN, LEN, CMP, CMP, CMP, CMP, CMP,
      /* S_F */  CMP, CMP, CMP, CMP, CMP, LEN, CMP, CMP,
                 CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
      /* S_Z */  CMP,  1,   1,  CMP, -1,  CMP, CMP, CMP,
                 -1,  CMP, CMP, CMP
  };

  if (p1 == p2)
    return 0;

  c1 = *p1++;
  c2 = *p2++;
  /* Hint: '0' is a digit too.  */
  state = S_N | ((c1 == '0') + (ISDIGIT (c1) != 0));

  while ((diff = c1 - c2) == 0 && c1 != '\0')
    {
      state = next_state[state];
      c1 = *p1++;
      c2 = *p2++;
      state |= (c1 == '0') + (ISDIGIT (c1) != 0);
    }

  state = result_type[state << 2 | ((c2 == '0') + (ISDIGIT (c2) != 0))];

  switch (state)
    {
    case CMP:
      return diff;

    case LEN:
      while (ISDIGIT (*p1++))
        if (!ISDIGIT (*p2++))
          return 1;

      return ISDIGIT (*p2) ? -1 : diff;

    default:
      return state;
    }
}
#ifdef weak_alias
weak_alias (__strverscmp, strverscmp)
#endif