FSPath::starts_with

3 files changed, 42 insertions, 0 deletions

diff --git a/paludis/util/fs_path.cc b/paludis/util/fs_path.cc
index 3fd1eeb..ff7b303 100644
--- a/paludis/util/fs_path.cc
+++ b/paludis/util/fs_path.cc
@@ -196,6 +196,17 @@ FSPath::strip_leading(const FSPath & f) const
     return FSPath(_imp->path.substr(root.length()));
 }
 
+bool
+FSPath::starts_with(const FSPath & f) const
+{
+    std::string root(stringify(f));
+
+    if (root == "/")
+        root.clear();
+    root.append("/");
+    return 0 == (_imp->path + "/").compare(0, root.length(), root);
+}
+
 FSPath
 FSPath::dirname() const
 {
diff --git a/paludis/util/fs_path.hh b/paludis/util/fs_path.hh
index f18fa61..bb9c65a 100644
--- a/paludis/util/fs_path.hh
+++ b/paludis/util/fs_path.hh
@@ -85,6 +85,12 @@ namespace paludis
             FSPath strip_leading(const FSPath & prefix) const;
 
             /**
+             * Do we start with a given path (eg '/foo/bar' starts with '/foo'
+             * but not '/fo')?
+             */
+            bool starts_with(const FSPath &) const;
+
+            /**
              * Try to make a directory.
              *
              * \return True, if we succeeded, and false if the directory
diff --git a/paludis/util/fs_path_TEST.cc b/paludis/util/fs_path_TEST.cc
index 095db0f..3a87d13 100644
--- a/paludis/util/fs_path_TEST.cc
+++ b/paludis/util/fs_path_TEST.cc
@@ -107,6 +107,31 @@ TEST(FSPath, StripLeading)
     EXPECT_TRUE(stringify(d.strip_leading(root3)) == "/my/directory");
 }
 
+TEST(FSPath, StartsWith)
+{
+    FSPath slash("/");
+    FSPath usr("/usr");
+    FSPath lib("/lib");
+
+    EXPECT_TRUE(FSPath("/").starts_with(slash));
+    EXPECT_TRUE(FSPath("/usr").starts_with(slash));
+    EXPECT_TRUE(FSPath("/usr/bin/foo").starts_with(slash));
+    EXPECT_TRUE(FSPath("/lib/foo").starts_with(slash));
+    EXPECT_TRUE(FSPath("/lib64/foo").starts_with(slash));
+
+    EXPECT_FALSE(FSPath("/").starts_with(usr));
+    EXPECT_TRUE(FSPath("/usr").starts_with(usr));
+    EXPECT_TRUE(FSPath("/usr/bin/foo").starts_with(usr));
+    EXPECT_FALSE(FSPath("/lib/foo").starts_with(usr));
+    EXPECT_FALSE(FSPath("/lib64/foo").starts_with(usr));
+
+    EXPECT_FALSE(FSPath("/").starts_with(lib));
+    EXPECT_FALSE(FSPath("/usr").starts_with(lib));
+    EXPECT_FALSE(FSPath("/usr/bin/foo").starts_with(lib));
+    EXPECT_TRUE(FSPath("/lib/foo").starts_with(lib));
+    EXPECT_FALSE(FSPath("/lib64/foo").starts_with(lib));
+}
+
 TEST(FSPath, OStream)
 {
     std::string n("fs_path_TEST_dir/no_perms");