filesystem: add device number utilities

Add a utility type and functions for handling device numbers.

1 files changed, 54 insertions, 0 deletions

diff --git a/filesystem/path_test.go b/filesystem/path_test.go
new file mode 100644
index 0000000..eef5ce3
--- /dev/null
+++ b/filesystem/path_test.go
@@ -0,0 +1,54 @@
+/*
+ * path_test.go - Tests for path utilities.
+ *
+ * Copyright 2019 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+package filesystem
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestDeviceNumber(t *testing.T) {
+	num, err := getDeviceNumber("/NONEXISTENT")
+	if num != 0 || err == nil {
+		t.Error("Should have failed to get device number of nonexistent file")
+	}
+	// /dev/null is always device 1:3 on Linux.
+	num, err = getDeviceNumber("/dev/null")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if str := num.String(); str != "1:3" {
+		t.Errorf("Wrong device number string: %q", str)
+	}
+	if str := fmt.Sprintf("%v", num); str != "1:3" {
+		t.Errorf("Wrong device number string: %q", str)
+	}
+	var num2 DeviceNumber
+	num2, err = newDeviceNumberFromString("1:3")
+	if err != nil {
+		t.Error("Failed to parse device number")
+	}
+	if num2 != num {
+		t.Errorf("Wrong device number: %d", num2)
+	}
+	num2, err = newDeviceNumberFromString("foo")
+	if num2 != 0 || err == nil {
+		t.Error("Should have failed to parse invalid device number")
+	}
+}