version.c

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/*
 *  Copyright (c) 2006-2011 Pacman Development Team <pacman-dev@archlinux.org>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program 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 General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

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

/* libalpm */
#include "util.h"

/**
 * Some functions in this file have been adopted from the rpm source, notably
 * 'rpmvercmp' located at lib/rpmvercmp.c and 'parseEVR' located at
 * lib/rpmds.c. It was most recently updated against rpm version 4.8.1. Small
 * modifications have been made to make it more consistent with the libalpm
 * coding style.
 */

/**
 * Split EVR into epoch, version, and release components.
 * @param evr       [epoch:]version[-release] string
 * @retval *ep      pointer to epoch
 * @retval *vp      pointer to version
 * @retval *rp      pointer to release
 */
static void parseEVR(char *evr, const char **ep, const char **vp,
        const char **rp)
{
    const char *epoch;
    const char *version;
    const char *release;
    char *s, *se;

    s = evr;
    /* s points to epoch terminator */
    while (*s && isdigit(*s)) s++;
    /* se points to version terminator */
    se = strrchr(s, '-');

    if(*s == ':') {
        epoch = evr;
        *s++ = '\0';
        version = s;
        if(*epoch == '\0') {
            epoch = "0";
        }
    } else {
        /* different from RPM- always assume 0 epoch */
        epoch = "0";
        version = evr;
    }
    if(se) {
        *se++ = '\0';
        release = se;
    } else {
        release = NULL;
    }

    if(ep) *ep = epoch;
    if(vp) *vp = version;
    if(rp) *rp = release;
}

/**
 * Compare alpha and numeric segments of two versions.
 * return 1: a is newer than b
 *        0: a and b are the same version
 *       -1: b is newer than a
 */
static int rpmvercmp(const char *a, const char *b)
{
    char oldch1, oldch2;
    char *str1, *str2;
    char *ptr1, *ptr2;
    char *one, *two;
    int rc;
    int isnum;
    int ret = 0;

    /* easy comparison to see if versions are identical */
    if(strcmp(a, b) == 0) return 0;

    str1 = strdup(a);
    str2 = strdup(b);

    one = ptr1 = str1;
    two = ptr2 = str2;

    /* loop through each version segment of str1 and str2 and compare them */
    while (*one && *two) {
        while (*one && !isalnum((int)*one)) one++;
        while (*two && !isalnum((int)*two)) two++;

        /* If we ran to the end of either, we are finished with the loop */
        if (!(*one && *two)) break;

        /* If the separator lengths were different, we are also finished */
        if ((one - ptr1) != (two - ptr2)) {
            return (one - ptr1) < (two - ptr2) ? -1 : 1;
        }

        ptr1 = one;
        ptr2 = two;

        /* grab first completely alpha or completely numeric segment */
        /* leave one and two pointing to the start of the alpha or numeric */
        /* segment and walk ptr1 and ptr2 to end of segment */
        if (isdigit((int)*ptr1)) {
            while (*ptr1 && isdigit((int)*ptr1)) ptr1++;
            while (*ptr2 && isdigit((int)*ptr2)) ptr2++;
            isnum = 1;
        } else {
            while (*ptr1 && isalpha((int)*ptr1)) ptr1++;
            while (*ptr2 && isalpha((int)*ptr2)) ptr2++;
            isnum = 0;
        }

        /* save character at the end of the alpha or numeric segment */
        /* so that they can be restored after the comparison */
        oldch1 = *ptr1;
        *ptr1 = '\0';
        oldch2 = *ptr2;
        *ptr2 = '\0';

        /* this cannot happen, as we previously tested to make sure that */
        /* the first string has a non-null segment */
        if (one == ptr1) {
            ret = -1;   /* arbitrary */
            goto cleanup;
        }

        /* take care of the case where the two version segments are */
        /* different types: one numeric, the other alpha (i.e. empty) */
        /* numeric segments are always newer than alpha segments */
        /* XXX See patch #60884 (and details) from bugzilla #50977. */
        if (two == ptr2) {
            ret = isnum ? 1 : -1;
            goto cleanup;
        }

        if (isnum) {
            /* this used to be done by converting the digit segments */
            /* to ints using atoi() - it's changed because long  */
            /* digit segments can overflow an int - this should fix that. */

            /* throw away any leading zeros - it's a number, right? */
            while (*one == '0') one++;
            while (*two == '0') two++;

            /* whichever number has more digits wins */
            if (strlen(one) > strlen(two)) {
                ret = 1;
                goto cleanup;
            }
            if (strlen(two) > strlen(one)) {
                ret = -1;
                goto cleanup;
            }
        }

        /* strcmp will return which one is greater - even if the two */
        /* segments are alpha or if they are numeric.  don't return  */
        /* if they are equal because there might be more segments to */
        /* compare */
        rc = strcmp(one, two);
        if (rc) {
            ret = rc < 1 ? -1 : 1;
            goto cleanup;
        }

        /* restore character that was replaced by null above */
        *ptr1 = oldch1;
        one = ptr1;
        *ptr2 = oldch2;
        two = ptr2;
    }

    /* this catches the case where all numeric and alpha segments have */
    /* compared identically but the segment separating characters were */
    /* different */
    if ((!*one) && (!*two)) {
        ret = 0;
        goto cleanup;
    }

    /* the final showdown. we never want a remaining alpha string to
     * beat an empty string. the logic is a bit weird, but:
     * - if one is empty and two is not an alpha, two is newer.
     * - if one is an alpha, two is newer.
     * - otherwise one is newer.
     * */
    if ( (!*one && !isalpha((int)*two))
            || isalpha((int)*one) ) {
        ret = -1;
    } else {
        ret = 1;
    }

cleanup:
    free(str1);
    free(str2);
    return ret;
}

/** Compare two version strings and determine which one is 'newer'.
 * Returns a value comparable to the way strcmp works. Returns 1
 * if a is newer than b, 0 if a and b are the same version, or -1
 * if b is newer than a.
 *
 * Different epoch values for version strings will override any further
 * comparison. If no epoch is provided, 0 is assumed.
 *
 * Keep in mind that the pkgrel is only compared if it is available
 * on both versions handed to this function. For example, comparing
 * 1.5-1 and 1.5 will yield 0; comparing 1.5-1 and 1.5-2 will yield
 * -1 as expected. This is mainly for supporting versioned dependencies
 * that do not include the pkgrel.
 */
int SYMEXPORT alpm_pkg_vercmp(const char *a, const char *b)
{
    char *full1, *full2;
    const char *epoch1, *ver1, *rel1;
    const char *epoch2, *ver2, *rel2;
    int ret;

    /* ensure our strings are not null */
    if(!a && !b) {
        return 0;
    } else if(!a) {
        return -1;
    } else if(!b) {
        return 1;
    }
    /* another quick shortcut- if full version specs are equal */
    if(strcmp(a, b) == 0) {
        return 0;
    }

    /* Parse both versions into [epoch:]version[-release] triplets. We probably
     * don't need epoch and release to support all the same magic, but it is
     * easier to just run it all through the same code. */
    full1 = strdup(a);
    full2 = strdup(b);

    /* parseEVR modifies passed in version, so have to dupe it first */
    parseEVR(full1, &epoch1, &ver1, &rel1);
    parseEVR(full2, &epoch2, &ver2, &rel2);

    ret = rpmvercmp(epoch1, epoch2);
    if(ret == 0) {
        ret = rpmvercmp(ver1, ver2);
        if(ret == 0 && rel1 && rel2) {
            ret = rpmvercmp(rel1, rel2);
        }
    }

    free(full1);
    free(full2);
    return ret;
}

/* vim: set ts=2 sw=2 noet: */