dpkg: better and shorter code to compare versions

 (taken from "official" dpkg).
 By Eugene T. Bordenkircher (eugebo AT gmail.com)

function                                             old     new   delta
order                                                  -      48     +48
test_version                                         273     276      +3
version_compare_part                                 396     187    -209
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/1 up/down: 51/-209)          Total: -158 bytes

1 files changed, 59 insertions, 68 deletions

diff --git a/archival/dpkg.c b/archival/dpkg.c
index 1bc8d27ce..577b77fec 100644
--- a/archival/dpkg.c
+++ b/archival/dpkg.c
@@ -6,6 +6,10 @@
  *  written by glenn mcgrath with the help of others
  *  copyright (c) 2001 by glenn mcgrath
  *
+ *  parts of the version comparison code is plucked from the real dpkg
+ *  application which is licensed GPLv2 and
+ *  copyright (c) 1995 Ian Jackson <ian@chiark.greenend.org.uk>
+ *
  *  started life as a busybox implementation of udpkg
  *
  * licensed under gplv2 or later, see file license in this tarball for details.
@@ -135,7 +139,7 @@ static void make_hash(const char *key, unsigned *start, unsigned *decrement, con
                 /* shifts the ascii based value and adds it to previous value
                  * shift amount is mod 24 because long int is 32 bit and data
                  * to be shifted is 8, don't want to shift data to where it has
-                 * no effect*/
+                 * no effect */
                 hash_num += (key[i] + key[i-1]) << ((key[i] * i) % 24);
         }
         *start = (unsigned) hash_num % hash_prime;
@@ -183,60 +187,52 @@ static unsigned search_status_hashtable(const char *key)
         return probe_address;
 }
 
-/* Need to rethink version comparison, maybe the official dpkg has something i can use ? */
-static int version_compare_part(const char *version1, const char *version2)
+static int order(char x)
 {
-        int upstream_len1 = 0;
-        int upstream_len2 = 0;
-        char *name1_char;
-        char *name2_char;
-        int len1 = 0;
-        int len2 = 0;
-        int tmp_int;
-        int ver_num1;
-        int ver_num2;
-
-        if (version1 == NULL) {
-                version1 = xstrdup("");
-        }
-        if (version2 == NULL) {
-                version2 = xstrdup("");
-        }
-        upstream_len1 = strlen(version1);
-        upstream_len2 = strlen(version2);
-
-        while ((len1 < upstream_len1) || (len2 < upstream_len2)) {
-                /* Compare non-digit section */
-                tmp_int = strcspn(&version1[len1], "0123456789");
-                name1_char = xstrndup(&version1[len1], tmp_int);
-                len1 += tmp_int;
-                tmp_int = strcspn(&version2[len2], "0123456789");
-                name2_char = xstrndup(&version2[len2], tmp_int);
-                len2 += tmp_int;
-                tmp_int = strcmp(name1_char, name2_char);
-                free(name1_char);
-                free(name2_char);
-                if (tmp_int != 0) {
-                        return tmp_int;
+        return (x == '~' ? -1
+                : x == '\0' ? 0
+                : isdigit(x) ? 0
+                : isalpha(x) ? x
+                : (unsigned char)x + 256
+        );
+}
+
+/* This code is taken from dpkg and modified slightly to work with busybox */
+static int version_compare_part(const char *val, const char *ref)
+{
+        if (!val) val = "";
+        if (!ref) ref = "";
+
+        while (*val || *ref) {
+                int first_diff;
+
+                while ((*val && !isdigit(*val)) || (*ref && !isdigit(*ref))) {
+                        int vc = order(*val);
+                        int rc = order(*ref);
+                        if (vc != rc)
+                                return vc - rc;
+                        val++;
+                        ref++;
                 }
 
-                /* Compare digits */
-                tmp_int = strspn(&version1[len1], "0123456789");
-                name1_char = xstrndup(&version1[len1], tmp_int);
-                len1 += tmp_int;
-                tmp_int = strspn(&version2[len2], "0123456789");
-                name2_char = xstrndup(&version2[len2], tmp_int);
-                len2 += tmp_int;
-                ver_num1 = atoi(name1_char);
-                ver_num2 = atoi(name2_char);
-                free(name1_char);
-                free(name2_char);
-                if (ver_num1 < ver_num2) {
-                        return -1;
+                while (*val == '0')
+                        val++;
+                while (*ref == '0')
+                        ref++;
+
+                first_diff = 0;
+                while (isdigit(*val) && isdigit(*ref)) {
+                        if (first_diff == 0)
+                                first_diff = *val - *ref;
+                        val++;
+                        ref++;
                 }
-                if (ver_num1 > ver_num2) {
+                if (isdigit(*val))
                         return 1;
-                }
+                if (isdigit(*ref))
+                        return -1;
+                if (first_diff)
+                        return first_diff;
         }
         return 0;
 }
@@ -249,39 +245,34 @@ static int version_compare(const unsigned ver1, const unsigned ver2)
 {
         char *ch_ver1 = name_hashtable[ver1];
         char *ch_ver2 = name_hashtable[ver2];
-
-        char epoch1, epoch2;
+        unsigned long epoch1 = 0, epoch2 = 0;
+        char *colon;
         char *deb_ver1, *deb_ver2;
-        char *ver1_ptr, *ver2_ptr;
         char *upstream_ver1;
         char *upstream_ver2;
         int result;
 
         /* Compare epoch */
-        if (ch_ver1[1] == ':') {
-                epoch1 = ch_ver1[0];
-                ver1_ptr = strchr(ch_ver1, ':') + 1;
-        } else {
-                epoch1 = '0';
-                ver1_ptr = ch_ver1;
+        colon = strchr(ch_ver1, ':');
+        if (colon) {
+                epoch1 = atoi(ch_ver1);
+                ch_ver1 = colon + 1;
         }
-        if (ch_ver2[1] == ':') {
-                epoch2 = ch_ver2[0];
-                ver2_ptr = strchr(ch_ver2, ':') + 1;
-        } else {
-                epoch2 = '0';
-                ver2_ptr = ch_ver2;
+        colon = strchr(ch_ver2, ':');
+        if (colon) {
+                epoch2 = atoi(ch_ver2);
+                ch_ver2 = colon + 1;
         }
         if (epoch1 < epoch2) {
                 return -1;
         }
-        else if (epoch1 > epoch2) {
+        if (epoch1 > epoch2) {
                 return 1;
         }
 
         /* Compare upstream version */
-        upstream_ver1 = xstrdup(ver1_ptr);
-        upstream_ver2 = xstrdup(ver2_ptr);
+        upstream_ver1 = xstrdup(ch_ver1);
+        upstream_ver2 = xstrdup(ch_ver2);
 
         /* Chop off debian version, and store for later use */
         deb_ver1 = strrchr(upstream_ver1, '-');