LogDog: Add Butler stream server package.

client/internal/logdog/butler/streamserver/namedPipe_posix.go

Index: client/internal/logdog/butler/streamserver/namedPipe_posix.go
diff --git a/client/internal/logdog/butler/streamserver/namedPipe_posix.go b/client/internal/logdog/butler/streamserver/namedPipe_posix.go
new file mode 100644
index 0000000000000000000000000000000000000000..74f59bc130b975b63b9fe1dcc426485d5ff8b291
--- /dev/null
+++ b/client/internal/logdog/butler/streamserver/namedPipe_posix.go
@@ -0,0 +1,66 @@
+// 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 streamserver
+
+import (
+	"net"
+	"os"
+
+	log "github.com/luci/luci-go/common/logging"
+	"golang.org/x/net/context"
+)
+
+// NewNamedPipeServer instantiates a new POSIX named pipe server instance.
+func NewNamedPipeServer(ctx context.Context, path string) StreamServer {
+	ctx = log.SetField(ctx, "namedPipePath", path)
+	return createNamedPipeServer(ctx, func() (net.Listener, error) {
+		log.Infof(ctx, "Creating POSIX server socket Listener.")
+
+		// Cleanup any previous named pipe. We don't bother checking for the file
+		// first since the remove is atomic. We also ignore any error here, since
+		// it's probably related to the file not being found.
+		//
+		// If there was an actual error removing the file, we'll catch it shortly
+		// when we try to create it.
+		os.Remove(path)
+
+		// Create a UNIX listener
+		l, err := net.Listen("unix", path)
+		if err != nil {
+			return nil, err
+		}
+
+		ul := selfCleaningUNIXListener{
+			Context:  ctx,
+			Listener: l,
+			path:     path,
+		}
+		return &ul, nil
+	})
+}
+
+// Wrapper around the "unix"-type Listener that cleans up the named pipe on
+// creation and 'Close()'
+type selfCleaningUNIXListener struct {
+	context.Context
+	net.Listener
+
+	path string
+}
+
+func (l *selfCleaningUNIXListener) Close() error {
+	if err := l.Listener.Close(); err != nil {
+		return err
+	}
+
+	if err := os.Remove(l.path); err != nil {
+		log.Fields{
+			log.ErrorKey: err,
+		}.Warningf(l, "Failed to remove named pipe file on Close().")
+	}
+	return nil
+}