UnionFs: Implement Truncate

unionfs/unionfs.go

@@ -321,6 +321,18 @@ func (me *UnionFs) Symlink(pointedTo string, linkName string) (code fuse.Status)
 	return code
 }
 
+func (me *UnionFs) Truncate(path string, offset uint64) (code fuse.Status) {
+	branch := me.getBranch(path)
+	if branch > 0 {
+		code := me.Promote(path, me.branches[branch])
+		if code != fuse.OK {
+			return code
+		}
+	}
+	
+	return me.fileSystems[0].Truncate(path, offset)
+}
+
 func (me *UnionFs) Chmod(name string, mode uint32) (code fuse.Status) {
 	r := me.branchCache.Get(name).(getBranchResult)
 	if r.attr == nil || r.code != fuse.OK {

unionfs/unionfs_test.go

@@ -333,3 +333,20 @@ func TestWritableDir(t *testing.T) {
 		t.Errorf("unexpected permission %o", fi.Permission())
 	}
 }
+
+func TestTruncate(t *testing.T) {
+	t.Log("TestTruncate")
+	wd, state := setup(t)
+	defer state.Unmount()
+
+	writeToFile(wd+"/ro/file", "hello")
+	os.Truncate(wd+"/mount/file", 2)
+	content := readFromFile(wd+"/mount/file")
+	if content != "he" {
+		t.Errorf("unexpected content %v", content)
+	}
+	content2 := readFromFile(wd+"/rw/file")
+	if content2 != content {
+		t.Errorf("unexpected rw content %v", content2)
+	}
+}