[mLib] / utils / versioncmp.c

/* -*-c-*-
 *
 * Compare version numbers using the Debian algorithm
 *
 * (c) 2007 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of the mLib utilities library.
 *
 * mLib 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.
 *
 * mLib 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 mLib; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Header files ------------------------------------------------------*/

#include <ctype.h>
#include <string.h>

#include "versioncmp.h"

/*----- Main code ---------------------------------------------------------*/

/* --- @versioncmp@ --- *
 *
 * Arguments:   @const char *va, *vb@ = two version strings
 *
 * Returns:     Less than, equal to, or greater than zero, according to
 *              whether @va@ is less than, equal to, or greater than @vb@.
 *
 * Use:         Compares version number strings.
 *
 *              The algorithm is an extension of the Debian version
 *              comparison algorithm.  A version number consists of three
 *              components:
 *
 *                [EPOCH :] MAIN [- SUB]
 *
 *              The MAIN part may contain colons or hyphens if there is an
 *              EPOCH or SUB, respectively.  Version strings are compared
 *              componentwise: first epochs, then main parts, and finally
 *              subparts.
 *
 *              The component comparison is done as follows.  First, the
 *              initial subsequence of nondigit characters is extracted from
 *              each string, and these are compared lexicographically, using
 *              ASCII ordering, except that letters precede non-letters.  If
 *              both are the same, an initial sequence of digits is extracted
 *              from the remaining parts of the version strings, and these
 *              are compared numerically (an empty sequence being considered
 *              to have the value zero).  This process is repeated until we
 *              have a winner or until both strings are exhausted.
 */

struct vinfo {
  const char *e, *el;
  const char *m, *ml;
  const char *s, *sl;
};

static int vint(const char **vv, const char *vl)
{
  int n = 0;
  const char *v = *vv;
  int ch;

  while (v < vl) {
    ch = *v;
    if (!isdigit((unsigned char)ch))
      break;
    v++;
    n = n * 10 + (ch - '0');
  }
  *vv = v;
  return (n);
}

static const char *vchr(const char **vv, const char *vl)
{
  const char *v = *vv;
  const char *b = v;
  int ch;

  while (v < vl) {
    ch = *v;
    if (isdigit((unsigned char)ch))
      break;
    v++;
  }
  *vv = v;
  return (b);
}

#define CMP(x, y) ((x) < (y) ? -1 : +1)

static int vcmp(const char *va, const char *val,
                const char *vb, const char *vbl)
{
  const char *pa, *pb;
  int ia, ib;

  for (;;) {

    /* --- See if we're done --- */

    if (va == val && vb == vbl)
      return (0);

    /* --- Compare nondigit portions --- */

    pa = vchr(&va, val); pb = vchr(&vb, vbl);
    for (;;) {
      if (pa == va) ia = 1;
      else if (isalpha((unsigned char)*pa)) ia = 2;
      else if (*pa == '~') ia = 0;
      else ia = 3;

      if (pb == vb) ib = 1;
      else if (isalpha((unsigned char)*pb)) ib = 2;
      else if (*pb == '~') ib = 0;
      else ib = 3;

      if (ia != ib) return (CMP(ia, ib));
      else if (pa == va && pb == vb) break;
      else if (*pa != *pb) return (CMP(*pa, *pb));
      pa++; pb++;
    }

    /* --- Compare digit portions --- */

    ia = vint(&va, val); ib = vint(&vb, vbl);
    if (ia != ib) return (CMP(ia, ib));
  }
}

static void vsplit(const char *v, struct vinfo *vi)
{
  const char *p;
  size_t n;

  if ((p = strchr(v, ':')) == 0)
    vi->e = vi->el = 0;
  else {
    vi->e = v;
    vi->el = p;
    v = p + 1;
  }

  n = strlen(v);
  if ((p = strrchr(v, '-')) == 0)
    vi->s = vi->sl = 0;
  else {
    vi->s = p + 1;
    vi->sl = v + n;
    n = p - v;
  }

  vi->m = v;
  vi->ml = v + n;
}

int versioncmp(const char *va, const char *vb)
{
  struct vinfo via, vib;
  int rc;

  vsplit(va, &via); vsplit(vb, &vib);
  if ((rc = vcmp(via.e, via.el, vib.e, vib.el)) != 0 ||
      (rc = vcmp(via.m, via.ml, vib.m, vib.ml)) != 0 ||
      (rc = vcmp(via.s, via.sl, vib.s, vib.sl)) != 0)
    return (rc);
  return (0);
}

/*----- That's all, folks -------------------------------------------------*/