157 lines
5.2 KiB
C
157 lines
5.2 KiB
C
/* Compare strings while treating digits characters numerically.
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Copyright (C) 1997-2022 Free Software Foundation, Inc.
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This file is part of the libiberty library.
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Contributed by Jean-François Bignolles <bignolle@ecoledoc.ibp.fr>, 1997.
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Libiberty is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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Libiberty is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA. */
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#include "libiberty.h"
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#include "safe-ctype.h"
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/*
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@deftypefun int strverscmp (const char *@var{s1}, const char *@var{s2})
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The @code{strverscmp} function compares the string @var{s1} against
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@var{s2}, considering them as holding indices/version numbers. Return
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value follows the same conventions as found in the @code{strverscmp}
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function. In fact, if @var{s1} and @var{s2} contain no digits,
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@code{strverscmp} behaves like @code{strcmp}.
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Basically, we compare strings normally (character by character), until
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we find a digit in each string - then we enter a special comparison
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mode, where each sequence of digits is taken as a whole. If we reach the
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end of these two parts without noticing a difference, we return to the
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standard comparison mode. There are two types of numeric parts:
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"integral" and "fractional" (those begin with a '0'). The types
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of the numeric parts affect the way we sort them:
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@itemize @bullet
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@item
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integral/integral: we compare values as you would expect.
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@item
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fractional/integral: the fractional part is less than the integral one.
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Again, no surprise.
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@item
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fractional/fractional: the things become a bit more complex.
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If the common prefix contains only leading zeroes, the longest part is less
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than the other one; else the comparison behaves normally.
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@end itemize
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@smallexample
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strverscmp ("no digit", "no digit")
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@result{} 0 // @r{same behavior as strcmp.}
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strverscmp ("item#99", "item#100")
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@result{} <0 // @r{same prefix, but 99 < 100.}
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strverscmp ("alpha1", "alpha001")
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@result{} >0 // @r{fractional part inferior to integral one.}
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strverscmp ("part1_f012", "part1_f01")
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@result{} >0 // @r{two fractional parts.}
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strverscmp ("foo.009", "foo.0")
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@result{} <0 // @r{idem, but with leading zeroes only.}
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@end smallexample
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This function is especially useful when dealing with filename sorting,
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because filenames frequently hold indices/version numbers.
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@end deftypefun
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*/
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/* states: S_N: normal, S_I: comparing integral part, S_F: comparing
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fractional parts, S_Z: idem but with leading Zeroes only */
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#define S_N 0x0
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#define S_I 0x4
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#define S_F 0x8
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#define S_Z 0xC
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/* result_type: CMP: return diff; LEN: compare using len_diff/diff */
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#define CMP 2
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#define LEN 3
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/* Compare S1 and S2 as strings holding indices/version numbers,
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returning less than, equal to or greater than zero if S1 is less than,
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equal to or greater than S2 (for more info, see the Glibc texinfo doc). */
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int
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strverscmp (const char *s1, const char *s2)
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{
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const unsigned char *p1 = (const unsigned char *) s1;
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const unsigned char *p2 = (const unsigned char *) s2;
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unsigned char c1, c2;
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int state;
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int diff;
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/* Symbol(s) 0 [1-9] others (padding)
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Transition (10) 0 (01) d (00) x (11) - */
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static const unsigned int next_state[] =
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{
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/* state x d 0 - */
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/* S_N */ S_N, S_I, S_Z, S_N,
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/* S_I */ S_N, S_I, S_I, S_I,
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/* S_F */ S_N, S_F, S_F, S_F,
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/* S_Z */ S_N, S_F, S_Z, S_Z
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};
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static const int result_type[] =
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{
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/* state x/x x/d x/0 x/- d/x d/d d/0 d/-
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0/x 0/d 0/0 0/- -/x -/d -/0 -/- */
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/* S_N */ CMP, CMP, CMP, CMP, CMP, LEN, CMP, CMP,
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CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
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/* S_I */ CMP, -1, -1, CMP, +1, LEN, LEN, CMP,
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+1, LEN, LEN, CMP, CMP, CMP, CMP, CMP,
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/* S_F */ CMP, CMP, CMP, CMP, CMP, LEN, CMP, CMP,
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CMP, CMP, CMP, CMP, CMP, CMP, CMP, CMP,
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/* S_Z */ CMP, +1, +1, CMP, -1, CMP, CMP, CMP,
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-1, CMP, CMP, CMP
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};
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if (p1 == p2)
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return 0;
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c1 = *p1++;
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c2 = *p2++;
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/* Hint: '0' is a digit too. */
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state = S_N | ((c1 == '0') + (ISDIGIT (c1) != 0));
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while ((diff = c1 - c2) == 0 && c1 != '\0')
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{
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state = next_state[state];
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c1 = *p1++;
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c2 = *p2++;
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state |= (c1 == '0') + (ISDIGIT (c1) != 0);
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}
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state = result_type[state << 2 | (((c2 == '0') + (ISDIGIT (c2) != 0)))];
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switch (state)
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{
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case CMP:
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return diff;
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case LEN:
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while (ISDIGIT (*p1++))
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if (!ISDIGIT (*p2++))
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return 1;
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return ISDIGIT (*p2) ? -1 : diff;
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default:
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return state;
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}
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}
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