tendermint/internal/libs/protoio/writer.go

// Protocol Buffers for Go with Gadgets
//
// Copyright (c) 2013, The GoGo Authors. All rights reserved.
// http://github.com/gogo/protobuf
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Modified from original GoGo Protobuf to return number of bytes written.

package protoio

import (
	"bytes"
	"encoding/binary"
	"io"
	"sync"

	"github.com/gogo/protobuf/proto"
)

// NewDelimitedWriter writes a varint-delimited Protobuf message to a writer. It is
// equivalent to the gogoproto NewDelimitedWriter, except WriteMsg() also returns the
// number of bytes written, which is necessary in the p2p package.
func NewDelimitedWriter(w io.Writer) WriteCloser {
	return &varintWriter{w, make([]byte, binary.MaxVarintLen64), nil}
}

type varintWriter struct {
	w      io.Writer
	lenBuf []byte
	buffer []byte
}

func (w *varintWriter) WriteMsg(msg proto.Message) (int, error) {
	if m, ok := msg.(marshaler); ok {
		n, ok := getSize(m)
		if ok {
			if n+binary.MaxVarintLen64 >= len(w.buffer) {
				w.buffer = make([]byte, n+binary.MaxVarintLen64)
			}
			lenOff := binary.PutUvarint(w.buffer, uint64(n))
			_, err := m.MarshalTo(w.buffer[lenOff:])
			if err != nil {
				return 0, err
			}
			_, err = w.w.Write(w.buffer[:lenOff+n])
			return lenOff + n, err
		}
	}

	// fallback
	data, err := proto.Marshal(msg)
	if err != nil {
		return 0, err
	}
	length := uint64(len(data))
	n := binary.PutUvarint(w.lenBuf, length)
	_, err = w.w.Write(w.lenBuf[:n])
	if err != nil {
		return 0, err
	}
	_, err = w.w.Write(data)
	return len(data) + n, err
}

func (w *varintWriter) Close() error {
	if closer, ok := w.w.(io.Closer); ok {
		return closer.Close()
	}
	return nil
}

func varintWrittenBytes(m marshaler, size int) ([]byte, error) {
	buf := make([]byte, size+binary.MaxVarintLen64)
	n := binary.PutUvarint(buf, uint64(size))
	nw, err := m.MarshalTo(buf[n:])
	if err != nil {
		return nil, err
	}
	return buf[:n+nw], nil
}

var bufPool = &sync.Pool{
	New: func() interface{} {
		return new(bytes.Buffer)
	},
}

func MarshalDelimited(msg proto.Message) ([]byte, error) {
	// The goal here is to write proto message as is knowning already if
	// the exact size can be retrieved and if so just use that.
	if m, ok := msg.(marshaler); ok {
		size, ok := getSize(msg)
		if ok {
			return varintWrittenBytes(m, size)
		}
	}

	// Otherwise, go down the route of using proto.Marshal,
	// and use the buffer pool to retrieve a writer.
	buf := bufPool.Get().(*bytes.Buffer)
	defer bufPool.Put(buf)
	buf.Reset()
	_, err := NewDelimitedWriter(buf).WriteMsg(msg)
	if err != nil {
		return nil, err
	}
	// Given that we are reusing buffers, we should
	// make a copy of the returned bytes.
	bytesCopy := make([]byte, buf.Len())
	copy(bytesCopy, buf.Bytes())
	return bytesCopy, nil
}