libiberty/strverscmp.c

   1 /* Compare strings while treating digits characters numerically.
   2    Copyright (C) 1997-2017 Free Software Foundation, Inc.
   3    This file is part of the libiberty library.
   4    Contributed by Jean-François 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})
  26 The @code{strverscmp} function compares the string @var{s1} against
  27 @var{s2}, considering them as holding indices/version numbers.  Return
  28 value follows the same conventions as found in the @code{strverscmp}
  29 function.  In fact, if @var{s1} and @var{s2} contain no digits,
  30 @code{strverscmp} behaves like @code{strcmp}.
  31
  32 Basically, we compare strings normally (character by character), until
  33 we find a digit in each string - then we enter a special comparison
  34 mode, where each sequence of digits is taken as a whole.  If we reach the
  35 end of these two parts without noticing a difference, we return to the
  36 standard comparison mode.  There are two types of numeric parts:
  37 "integral" and "fractional" (those  begin with a '0'). The types
  38 of the numeric parts affect the way we sort them:
  39
  40 @itemize @bullet
  41 @item
  42 integral/integral: we compare values as you would expect.
  43
  44 @item
  45 fractional/integral: the fractional part is less than the integral one.
  46 Again, no surprise.
  47
  48 @item
  49 fractional/fractional: the things become a bit more complex.
  50 If the common prefix contains only leading zeroes, the longest part is less
  51 than the other one; else the comparison behaves normally.
  52 @end itemize
  53
  54 @smallexample
  55 strverscmp ("no digit", "no digit")
  56     @result{} 0    // @r{same behavior as strcmp.}
  57 strverscmp ("item#99", "item#100")
  58     @result{} <0   // @r{same prefix, but 99 < 100.}
  59 strverscmp ("alpha1", "alpha001")
  60     @result{} >0   // @r{fractional part inferior to integral one.}
  61 strverscmp ("part1_f012", "part1_f01")
  62     @result{} >0   // @r{two fractional parts.}
  63 strverscmp ("foo.009", "foo.0")
  64     @result{} <0   // @r{idem, but with leading zeroes only.}
  65 @end smallexample
  66
  67 This function is especially useful when dealing with filename sorting,
  68 because 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
  89 int
  90 strverscmp (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 }