windows/svc: add new package to help create and manage Windows services

Change-Id: I58bb446aaa387b31d8a9ff4217793a170b96a7e2
Reviewed-on: https://go-review.googlesource.com/9104
Reviewed-by: Rob Pike <r@golang.org>

windows/svc/eventlog/log.go

@@ -0,0 +1,70 @@
+// Copyright 2012 The Go 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 windows
+
+// Package eventlog implements access to Windows event log.
+//
+package eventlog
+
+import (
+	"errors"
+	"syscall"
+
+	"golang.org/x/sys/windows"
+)
+
+// Log provides access to the system log.
+type Log struct {
+	Handle windows.Handle
+}
+
+// Open retrieves a handle to the specified event log.
+func Open(source string) (*Log, error) {
+	return OpenRemote("", source)
+}
+
+// OpenRemote does the same as Open, but on different computer host.
+func OpenRemote(host, source string) (*Log, error) {
+	if source == "" {
+		return nil, errors.New("Specify event log source")
+	}
+	var s *uint16
+	if host != "" {
+		s = syscall.StringToUTF16Ptr(host)
+	}
+	h, err := windows.RegisterEventSource(s, syscall.StringToUTF16Ptr(source))
+	if err != nil {
+		return nil, err
+	}
+	return &Log{Handle: h}, nil
+}
+
+// Close closes event log l.
+func (l *Log) Close() error {
+	return windows.DeregisterEventSource(l.Handle)
+}
+
+func (l *Log) report(etype uint16, eid uint32, msg string) error {
+	ss := []*uint16{syscall.StringToUTF16Ptr(msg)}
+	return windows.ReportEvent(l.Handle, etype, 0, eid, 0, 1, 0, &ss[0], nil)
+}
+
+// Info writes an information event msg with event id eid to the end of event log l.
+// When EventCreate.exe is used, eid must be between 1 and 1000.
+func (l *Log) Info(eid uint32, msg string) error {
+	return l.report(windows.EVENTLOG_INFORMATION_TYPE, eid, msg)
+}
+
+// Warning writes an warning event msg with event id eid to the end of event log l.
+// When EventCreate.exe is used, eid must be between 1 and 1000.
+func (l *Log) Warning(eid uint32, msg string) error {
+	return l.report(windows.EVENTLOG_WARNING_TYPE, eid, msg)
+}
+
+// Error writes an error event msg with event id eid to the end of event log l.
+// When EventCreate.exe is used, eid must be between 1 and 1000.
+func (l *Log) Error(eid uint32, msg string) error {
+	return l.report(windows.EVENTLOG_ERROR_TYPE, eid, msg)
+}