From: Joel Rosdahl <joel@rosdahl.net>
Date: Sat, 28 Jul 2012 09:50:06 +0000 (+0200)
Subject: Improve get_relative_path and add unit tests
X-Git-Tag: v3.1.8~11
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a5f8e78c61867fe64881323018bbeca83a43f6a1;p=thirdparty%2Fccache.git

Improve get_relative_path and add unit tests
---

diff --git a/test/test_util.c b/test/test_util.c
index b8d24beeb..10478baa7 100644
--- a/test/test_util.c
+++ b/test/test_util.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2010 Joel Rosdahl
+ * Copyright (C) 2010, 2012 Joel Rosdahl
  *
  * 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
@@ -41,4 +41,32 @@ TEST(dirname)
 	CHECK_STR_EQ_FREE2("dir1/dir2", dirname("dir1/dir2/"));
 }
 
+TEST(common_dir_prefix_length)
+{
+	CHECK_UNS_EQ(0, common_dir_prefix_length("", ""));
+	CHECK_UNS_EQ(0, common_dir_prefix_length("/", "/"));
+	CHECK_UNS_EQ(0, common_dir_prefix_length("/", "/b"));
+	CHECK_UNS_EQ(0, common_dir_prefix_length("/a", "/b"));
+	CHECK_UNS_EQ(2, common_dir_prefix_length("/a", "/a"));
+	CHECK_UNS_EQ(2, common_dir_prefix_length("/a", "/a/b"));
+	CHECK_UNS_EQ(2, common_dir_prefix_length("/a/b", "/a/c"));
+	CHECK_UNS_EQ(4, common_dir_prefix_length("/a/b", "/a/b"));
+}
+
+TEST(get_relative_path)
+{
+	CHECK_STR_EQ_FREE2("a", get_relative_path("/doesn't matter", "a"));
+	CHECK_STR_EQ_FREE2("a/b", get_relative_path("/doesn't matter", "a/b"));
+	CHECK_STR_EQ_FREE2(".", get_relative_path("/a", "/a"));
+	CHECK_STR_EQ_FREE2("..", get_relative_path("/a/b", "/a"));
+	CHECK_STR_EQ_FREE2("b", get_relative_path("/a", "/a/b"));
+	CHECK_STR_EQ_FREE2("b/c", get_relative_path("/a", "/a/b/c"));
+	CHECK_STR_EQ_FREE2("../c", get_relative_path("/a/b", "/a/c"));
+	CHECK_STR_EQ_FREE2("../c/d", get_relative_path("/a/b", "/a/c/d"));
+	CHECK_STR_EQ_FREE2("../../c/d", get_relative_path("/a/b/c", "/a/c/d"));
+	CHECK_STR_EQ_FREE2("../..", get_relative_path("/a/b", "/"));
+	CHECK_STR_EQ_FREE2("../../c", get_relative_path("/a/b", "/c"));
+	CHECK_STR_EQ_FREE2("a/b", get_relative_path("/", "/a/b"));
+}
+
 TEST_SUITE_END
diff --git a/util.c b/util.c
index acfcd9db6..b48980006 100644
--- a/util.c
+++ b/util.c
@@ -964,7 +964,7 @@ same_executable_name(const char *s1, const char *s2)
 
 /*
  * Compute the length of the longest directory path that is common to two
- * strings.
+ * paths. s1 is assumed to be the path to a directory.
  */
 size_t
 common_dir_prefix_length(const char *s1, const char *s2)
@@ -976,7 +976,21 @@ common_dir_prefix_length(const char *s1, const char *s2)
 		++p1;
 		++p2;
 	}
-	while (p1 > s1 && ((*p1 && *p1 != '/' ) || (*p2 && *p2 != '/'))) {
+	if (*p2 == '/') {
+		/* s2 starts with "s1/". */
+		return p1 - s1;
+	}
+	if (!*p2) {
+		/* s2 is equal to s1. */
+		if (p2 == s2 + 1) {
+			/* Special case for s1 and s2 both being "/". */
+			return 0;
+		} else {
+			return p1 - s1;
+		}
+	}
+	/* Compute the common directory prefix */
+	while (p1 > s1 && *p1 != '/') {
 		p1--;
 		p2--;
 	}
@@ -984,8 +998,9 @@ common_dir_prefix_length(const char *s1, const char *s2)
 }
 
 /*
- * Compute a relative path from from to to. Assumes that both from and to are
- * well-formed and canonical. Caller frees.
+ * Compute a relative path from from (an absolute path to a directory) to to (a
+ * path). Assumes that both from and to are well-formed and canonical. Caller
+ * frees.
  */
 char *
 get_relative_path(const char *from, const char *to)
@@ -995,23 +1010,24 @@ get_relative_path(const char *from, const char *to)
 	const char *p;
 	char *result;
 
+	assert(from && from[0] == '/');
+	assert(to);
+
 	if (!*to || *to != '/') {
 		return x_strdup(to);
 	}
 
 	result = x_strdup("");
 	common_prefix_len = common_dir_prefix_length(from, to);
-	for (p = from + common_prefix_len; *p; p++) {
-		if (*p == '/') {
-			x_asprintf2(&result, "../%s", result);
+	if (common_prefix_len > 0 || !str_eq(from, "/")) {
+		for (p = from + common_prefix_len; *p; p++) {
+			if (*p == '/') {
+				x_asprintf2(&result, "../%s", result);
+			}
 		}
 	}
 	if (strlen(to) > common_prefix_len) {
-		p = to + common_prefix_len + 1;
-		while (*p == '/') {
-			p++;
-		}
-		x_asprintf2(&result, "%s%s", result, p);
+		x_asprintf2(&result, "%s%s", result, to + common_prefix_len + 1);
 	}
 	i = strlen(result) - 1;
 	while (i >= 0 && result[i] == '/') {