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

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#if HAVE_CONFIG_H
# 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.
   - It's guaranteed to evaluate its argument exactly once.
   - It's typically faster.
   Posix 1003.2-1992 section 2.5.2.1 page 50 lines 1556-1558 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) (c) - '0' <= 9)

/* 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;
    }
}