LogDog: Add Butler Output package.

client/logdog/butlerproto/doc.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.
-
-// Package butlerproto implements the LogDog Butler wire protocol. This protocol
-// wraps Butler messages that are published to Cloud Pub/Sub for LogDog
-// consumption.
-//
-// The protocol begins with a set of header bytes to identify and parameterize
-// the remaining data, followed by the data itself.
-//
-// Note that the Pub/Sub layer is assumed to provide both a total length (so no
-// need to length-prefix) and integrity (so no need to checksum).
-//
-// Header
-//
-// The header is a fixed four bytes which positively identify the message as a
-// Butler Pub/Sub message and describe the remaining data. Variant parameters
-// can use different magic numbers to identify different parameters.
-//
-// Two magic numbers are currently defined:
-//   - 0x10 0x6d 0x06 0x00 (LogDog protocol ButlerLogBundle Raw)
-//   - 0x10 0x6d 0x06 0x62 (LogDog protocol ButlerLogBundle GZip compressed)
-//
-// Data
-//
-// The data component is described by the header, and consists of all data in
-// the Pub/Sub message past the last header byte.
-package butlerproto