LogDog: Add Butler stream server package.

client/logdog/butlerlib/streamclient/client_namedPipe_posix.go

Index: client/logdog/butlerlib/streamclient/client_namedPipe_posix.go
diff --git a/client/logdog/butlerlib/streamclient/client_namedPipe_posix.go b/client/logdog/butlerlib/streamclient/client_namedPipe_posix.go
new file mode 100644
index 0000000000000000000000000000000000000000..404976cb71145fe04bb8284b40a5e68bcea8a63a
--- /dev/null
+++ b/client/logdog/butlerlib/streamclient/client_namedPipe_posix.go
@@ -0,0 +1,38 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd
+
+package streamclient
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"os"
+)
+
+// Register POSIX-only protocols.
+func init() {
+	registerProtocol("unix", newUnixSocketClient)
+}
+
+// newUnixSocketClient creates a new Client instance bound to a named pipe stream
+// server.
+//
+// newNPipeClient currently only works on POSIX (non-Windows) systems.
+func newUnixSocketClient(path string) (Client, error) {
+	// Ensure that the supplied path exists and is a named pipe.
+	info, err := os.Lstat(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to stat file [%s]: %s", path, err)
+	}
+	if info.Mode()&os.ModeSocket == 0 {
+		return nil, fmt.Errorf("not a named pipe: [%s]", path)
+	}
+
+	return &clientImpl{func() (io.WriteCloser, error) {
+		return net.Dial("unix", path)
+	}}, nil
+}