auc: compare versions using dpkg/opkg's verrevcmp

Using strcmp() to compare a version string doesn't work well.
Use verrevcmp() function from opkg instead.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

utils/auc/src/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.6)
+cmake_minimum_required(VERSION 2.6...3.12)
 
 PROJECT(auc C)
 ADD_DEFINITIONS(-Os -ggdb -Wall --std=gnu99 -Wmissing-declarations)

utils/auc/src/auc.c

@@ -17,6 +17,7 @@
 #define AUC_VERSION "unknown"
 #endif
 
+#include <ctype.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <dlfcn.h>
@@ -359,6 +360,58 @@ static int load_config() {
 	return 0;
 }
 
+/*
+ * libdpkg - Debian packaging suite library routines
+ * vercmp.c - comparison of version numbers
+ *
+ * Copyright (C) 1995 Ian Jackson <iwj10@cus.cam.ac.uk>
+ */
+
+/* assume ascii; warning: evaluates x multiple times! */
+#define order(x) ((x) == '~' ? -1 \
+		: isdigit((x)) ? 0 \
+		: !(x) ? 0 \
+		: isalpha((x)) ? (x) \
+		: (x) + 256)
+
+static int verrevcmp(const char *val, const char *ref)
+{
+	if (!val)
+		val = "";
+	if (!ref)
+		ref = "";
+
+	while (*val || *ref) {
+		int first_diff = 0;
+
+		while ((*val && !isdigit(*val)) || (*ref && !isdigit(*ref))) {
+			int vc = order(*val), rc = order(*ref);
+			if (vc != rc)
+				return vc - rc;
+			val++;
+			ref++;
+		}
+
+		while (*val == '0')
+			val++;
+		while (*ref == '0')
+			ref++;
+		while (isdigit(*val) && isdigit(*ref)) {
+			if (!first_diff)
+				first_diff = *val - *ref;
+			val++;
+			ref++;
+		}
+		if (isdigit(*val))
+			return 1;
+		if (isdigit(*ref))
+			return -1;
+		if (first_diff)
+			return first_diff;
+	}
+	return 0;
+}
+
 
 /**
  * UBUS response callbacks
@@ -409,7 +462,7 @@ static void pkglist_check_cb(struct ubus_request *req, int type, struct blob_att
 			continue;
 		}
 
-		cmpres = strcmp(blobmsg_get_string(cur), pkg->version);
+		cmpres = verrevcmp(blobmsg_get_string(cur), pkg->version);
 		if (cmpres < 0)
 			*status |= PKG_UPGRADE;