LogDog: Add Butler stream server package.

client/logdog/butlerlib/streamclient/client_npipe_posix.go

Index: client/logdog/butlerlib/streamclient/client_npipe_posix.go
diff --git a/client/logdog/butlerlib/streamclient/client_npipe_posix.go b/client/logdog/butlerlib/streamclient/client_npipe_posix.go
new file mode 100644
index 0000000000000000000000000000000000000000..404976cb71145fe04bb8284b40a5e68bcea8a63a
--- /dev/null
+++ b/client/logdog/butlerlib/streamclient/client_npipe_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

[estaab, 2015/11/06 22:09:44]

What does this line do?

[dnj (Google), 2015/11/07 16:47:41]

This makes it so that Go build will only include this file if the build platform
is one of the named platforms.

e.g., this file is ignored on Windows.

The Windows file has a similar feature due to it being named "_windows.go".
Unfortunately there isn't a POSIX-comprehensive version of that, so I have to
manually call out POSIX platforms.

+
+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
+}