/* http://rpm.org/api/4.4.2.2/rpmvercmp_8c-source.html */

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

#define xisalpha(c)             isalpha(c)
#define xisalnum(c)             isalnum(c)
#define xisdigit(c)             isdigit(c)

/* 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 */
int rpmvercmp(const char * a, const char * b)
{
    char oldch1, oldch2;
    char * str1, * str2;
    char * one, * two;
    int rc;
    int isnum;

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

    str1 = alloca(strlen(a) + 1);
    str2 = alloca(strlen(b) + 1);

    strcpy(str1, a);
    strcpy(str2, b);

    one = str1;
    two = str2;

    /* loop through each version segment of str1 and str2 and compare them */
    /*@-branchstate@*/
/*@-boundsread@*/
    while (*one && *two) {
        while (*one && !xisalnum(*one)) one++;
        while (*two && !xisalnum(*two)) two++;

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

        str1 = one;
        str2 = 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 str1 and str2 to end of segment */
        if (xisdigit(*str1)) {
            while (*str1 && xisdigit(*str1)) str1++;
            while (*str2 && xisdigit(*str2)) str2++;
            isnum = 1;
        } else {
            while (*str1 && xisalpha(*str1)) str1++;
            while (*str2 && xisalpha(*str2)) str2++;
            isnum = 0;
        }

        /* save character at the end of the alpha or numeric segment */
        /* so that they can be restored after the comparison */
/*@-boundswrite@*/
        oldch1 = *str1;
        *str1 = '\0';
        oldch2 = *str2;
        *str2 = '\0';
/*@=boundswrite@*/

        /* this cannot happen, as we previously tested to make sure that */
        /* the first string has a non-null segment */
        if (one == str1) return -1;     /* arbitrary */

        /* 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 == str2) return (isnum ? 1 : -1);

        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)) return 1;
            if (strlen(two) > strlen(one)) return -1;
        }

        /* 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) return (rc < 1 ? -1 : 1);

        /* restore character that was replaced by null above */
/*@-boundswrite@*/
        *str1 = oldch1;
        one = str1;
        *str2 = oldch2;
        two = str2;
/*@=boundswrite@*/
    }
    /*@=branchstate@*/
/*@=boundsread@*/

    /* this catches the case where all numeric and alpha segments have */
    /* compared identically but the segment sepparating characters were */
    /* different */
/*@-boundsread@*/
    if ((!*one) && (!*two)) return 0;

    /* whichever version still has characters left over wins */
    if (!*one) return -1; else return 1;
/*@=boundsread@*/
}

