syncthing/vendor/github.com/gogo/protobuf/codec/codec.go

// Protocol Buffers for Go with Gadgets
//
// Copyright (c) 2015, 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.

package codec

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

type Codec interface {
	Marshal(v interface{}) ([]byte, error)
	Unmarshal(data []byte, v interface{}) error
	String() string
}

type marshaler interface {
	MarshalTo(data []byte) (n int, err error)
}

func getSize(v interface{}) (int, bool) {
	if sz, ok := v.(interface {
		Size() (n int)
	}); ok {
		return sz.Size(), true
	} else if sz, ok := v.(interface {
		ProtoSize() (n int)
	}); ok {
		return sz.ProtoSize(), true
	} else {
		return 0, false
	}
}

type codec struct {
	buf []byte
}

func (this *codec) String() string {
	return "proto"
}

func New(size int) Codec {
	return &codec{make([]byte, size)}
}

func (this *codec) Marshal(v interface{}) ([]byte, error) {
	if m, ok := v.(marshaler); ok {
		n, ok := getSize(v)
		if !ok {
			return proto.Marshal(v.(proto.Message))
		}
		if n > len(this.buf) {
			this.buf = make([]byte, n)
		}
		_, err := m.MarshalTo(this.buf)
		if err != nil {
			return nil, err
		}
		return this.buf[:n], nil
	}
	return proto.Marshal(v.(proto.Message))
}

func (this *codec) Unmarshal(data []byte, v interface{}) error {
	return proto.Unmarshal(data, v.(proto.Message))
}