1/* Compare strings while treating digits characters numerically.
2   Copyright (C) 1997, 2002, 2005 Free Software Foundation, Inc.
3   This file is part of the libiberty library.
4   Contributed by Jean-Fran�ois Bignolles <bignolle@ecoledoc.ibp.fr>, 1997.
5
6   Libiberty is free software; you can redistribute it and/or
7   modify it under the terms of the GNU Lesser General Public
8   License as published by the Free Software Foundation; either
9   version 2.1 of the License, or (at your option) any later version.
10
11   Libiberty 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   Lesser General Public License for more details.
15
16   You should have received a copy of the GNU Lesser General Public
17   License along with the GNU C Library; if not, write to the Free
18   Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
19   02110-1301 USA.  */
20
21#include "libiberty.h"
22#include "safe-ctype.h"
23
24/*
25@deftypefun int strverscmp (const char *@var{s1}, const char *@var{s2})
26The @code{strverscmp} function compares the string @var{s1} against
27@var{s2}, considering them as holding indices/version numbers.  Return
28value follows the same conventions as found in the @code{strverscmp}
29function.  In fact, if @var{s1} and @var{s2} contain no digits,
30@code{strverscmp} behaves like @code{strcmp}.
31
32Basically, we compare strings normally (character by character), until
33we find a digit in each string - then we enter a special comparison
34mode, where each sequence of digits is taken as a whole.  If we reach the
35end of these two parts without noticing a difference, we return to the
36standard comparison mode.  There are two types of numeric parts:
37"integral" and "fractional" (those  begin with a '0'). The types
38of the numeric parts affect the way we sort them:
39
40@itemize @bullet
41@item
42integral/integral: we compare values as you would expect.
43
44@item
45fractional/integral: the fractional part is less than the integral one.
46Again, no surprise.
47
48@item
49fractional/fractional: the things become a bit more complex.
50If the common prefix contains only leading zeroes, the longest part is less
51than the other one; else the comparison behaves normally.
52@end itemize
53
54@smallexample
55strverscmp ("no digit", "no digit")
56    @result{} 0    // @r{same behavior as strcmp.}
57strverscmp ("item#99", "item#100")
58    @result{} <0   // @r{same prefix, but 99 < 100.}
59strverscmp ("alpha1", "alpha001")
60    @result{} >0   // @r{fractional part inferior to integral one.}
61strverscmp ("part1_f012", "part1_f01")
62    @result{} >0   // @r{two fractional parts.}
63strverscmp ("foo.009", "foo.0")
64    @result{} <0   // @r{idem, but with leading zeroes only.}
65@end smallexample
66
67This function is especially useful when dealing with filename sorting,
68because filenames frequently hold indices/version numbers.
69@end deftypefun
70
71*/
72
73/* states: S_N: normal, S_I: comparing integral part, S_F: comparing
74           fractional parts, S_Z: idem but with leading Zeroes only */
75#define  S_N    0x0
76#define  S_I    0x4
77#define  S_F    0x8
78#define  S_Z    0xC
79
80/* result_type: CMP: return diff; LEN: compare using len_diff/diff */
81#define  CMP    2
82#define  LEN    3
83
84
85/* Compare S1 and S2 as strings holding indices/version numbers,
86   returning less than, equal to or greater than zero if S1 is less than,
87   equal to or greater than S2 (for more info, see the Glibc texinfo doc).  */
88
89int
90strverscmp (const char *s1, const char *s2)
91{
92  const unsigned char *p1 = (const unsigned char *) s1;
93  const unsigned char *p2 = (const unsigned char *) s2;
94  unsigned char c1, c2;
95  int state;
96  int diff;
97
98  /* Symbol(s)    0       [1-9]   others  (padding)
99     Transition   (10) 0  (01) d  (00) x  (11) -   */
100  static const unsigned int next_state[] =
101    {
102      /* state    x    d    0    - */
103      /* S_N */  S_N, S_I, S_Z, S_N,
104      /* S_I */  S_N, S_I, S_I, S_I,
105      /* S_F */  S_N, S_F, S_F, S_F,
106      /* S_Z */  S_N, S_F, S_Z, S_Z
107    };
108
109  static const int result_type[] =
110    {
111      /* state   x/x  x/d  x/0  x/-  d/x  d/d  d/0  d/-
112                 0/x  0/d  0/0  0/-  -/x  -/d  -/0  -/- */
113
114      /* S_N */  CMP, CMP, CMP, CMP, CMP, LEN, CMP, CMP,
115                 CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
116      /* S_I */  CMP, -1,  -1,  CMP, +1,  LEN, LEN, CMP,
117                 +1,  LEN, LEN, CMP, CMP, CMP, CMP, CMP,
118      /* S_F */  CMP, CMP, CMP, CMP, CMP, LEN, CMP, CMP,
119                 CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
120      /* S_Z */  CMP, +1,  +1,  CMP, -1,  CMP, CMP, CMP,
121                 -1,  CMP, CMP, CMP
122    };
123
124  if (p1 == p2)
125    return 0;
126
127  c1 = *p1++;
128  c2 = *p2++;
129  /* Hint: '0' is a digit too.  */
130  state = S_N | ((c1 == '0') + (ISDIGIT (c1) != 0));
131
132  while ((diff = c1 - c2) == 0 && c1 != '\0')
133    {
134      state = next_state[state];
135      c1 = *p1++;
136      c2 = *p2++;
137      state |= (c1 == '0') + (ISDIGIT (c1) != 0);
138    }
139
140  state = result_type[state << 2 | (((c2 == '0') + (ISDIGIT (c2) != 0)))];
141
142  switch (state)
143    {
144    case CMP:
145      return diff;
146
147    case LEN:
148      while (ISDIGIT (*p1++))
149	if (!ISDIGIT (*p2++))
150	  return 1;
151
152      return ISDIGIT (*p2) ? -1 : diff;
153
154    default:
155      return state;
156    }
157}
158