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/* Compare strings while treating digits characters numerically.

   Copyright (C) 1997, 2002, 2005 Free Software Foundation, Inc.

   This file is part of the libiberty library.

   Contributed by Jean-François Bignolles <bignolle@ecoledoc.ibp.fr>, 1997.

   Libiberty 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 of the License, or (at your option) any later version.

   Libiberty 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 the GNU C Library; if not, write to the Free

   Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

   02110-1301 USA.  */

#include "libiberty.h"

#include "safe-ctype.h"

/*

@deftypefun int strverscmp (const char *@var{s1}, const char *@var{s2})

The @code{strverscmp} function compares the string @var{s1} against

@var{s2}, considering them as holding indices/version numbers.  Return

value follows the same conventions as found in the @code{strverscmp}

function.  In fact, if @var{s1} and @var{s2} contain no digits,

@code{strverscmp} behaves like @code{strcmp}.

Basically, we compare strings normally (character by character), until

we find a digit in each string - then we enter a special comparison

mode, where each sequence of digits is taken as a whole.  If we reach the

end of these two parts without noticing a difference, we return to the

standard comparison mode.  There are two types of numeric parts:

"integral" and "fractional" (those  begin with a '0'). The types

of the numeric parts affect the way we sort them:

@itemize @bullet

@item

integral/integral: we compare values as you would expect.

@item

fractional/integral: the fractional part is less than the integral one.

Again, no surprise.

@item

fractional/fractional: the things become a bit more complex.

If the common prefix contains only leading zeroes, the longest part is less

than the other one; else the comparison behaves normally.

@end itemize

@smallexample

strverscmp ("no digit", "no digit")

    @result{} 0    // @r{same behavior as strcmp.}

strverscmp ("item#99", "item#100")

    @result{} <0   // @r{same prefix, but 99 < 100.}

strverscmp ("alpha1", "alpha001")

    @result{} >0   // @r{fractional part inferior to integral one.}

strverscmp ("part1_f012", "part1_f01")

    @result{} >0   // @r{two fractional parts.}

strverscmp ("foo.009", "foo.0")

    @result{} <0   // @r{idem, but with leading zeroes only.}

@end smallexample

This function is especially useful when dealing with filename sorting,

because filenames frequently hold indices/version numbers.

@end deftypefun

*/

/* 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

/* 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 Glibc 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;

    }

}