utils: Add lxc_append_paths to join two paths.

Signed-off-by: Christian Seiler <christian@iwakd.de>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>

src/lxc/utils.c

@@ -658,6 +658,25 @@ char **lxc_normalize_path(const char *path)
 	return components;
 }
 
+char *lxc_append_paths(const char *first, const char *second)
+{
+	size_t len = strlen(first) + strlen(second) + 1;
+	const char *pattern = "%s%s";
+	char *result = NULL;
+
+	if (second[0] != '/') {
+		len += 1;
+		pattern = "%s/%s";
+	}
+
+	result = calloc(1, len);
+	if (!result)
+		return NULL;
+
+	snprintf(result, len, pattern, first, second);
+	return result;
+}
+
 bool lxc_string_in_list(const char *needle, const char *haystack, char _sep)
 {
 	char *token, *str, *saveptr = NULL;

src/lxc/utils.h

@@ -219,6 +219,7 @@ extern char *lxc_string_join(const char *sep, const char **parts, bool use_as_pr
  *     foo//bar     ->   { foo, bar, NULL }
  */
 extern char **lxc_normalize_path(const char *path);
+extern char *lxc_append_paths(const char *first, const char *second);
 /* Note: the following two functions use strtok(), so they will never
  *       consider an empty element, even if two delimiters are next to
  *       each other.