LogDog: Add Butler stream server package.

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

+// 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
+}