137 lines
4.1 KiB
Go
137 lines
4.1 KiB
Go
// Copyright (c) 2013-2016 The btcsuite developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package wire
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import (
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"fmt"
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"io"
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)
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// MaxBlockHeadersPerMsg is the maximum number of block headers that can be in
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// a single bitcoin headers message.
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const MaxBlockHeadersPerMsg = 2000
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// MsgHeaders implements the Message interface and represents a bitcoin headers
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// message. It is used to deliver block header information in response
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// to a getheaders message (MsgGetHeaders). The maximum number of block headers
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// per message is currently 2000. See MsgGetHeaders for details on requesting
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// the headers.
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type MsgHeaders struct {
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Headers []*BlockHeader
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}
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// AddBlockHeader adds a new block header to the message.
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func (msg *MsgHeaders) AddBlockHeader(bh *BlockHeader) error {
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if len(msg.Headers)+1 > MaxBlockHeadersPerMsg {
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str := fmt.Sprintf("too many block headers in message [max %v]",
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MaxBlockHeadersPerMsg)
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return messageError("MsgHeaders.AddBlockHeader", str)
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}
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msg.Headers = append(msg.Headers, bh)
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return nil
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}
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// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
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// This is part of the Message interface implementation.
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func (msg *MsgHeaders) BtcDecode(r io.Reader, pver uint32, enc MessageEncoding) error {
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count, err := ReadVarInt(r, pver)
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if err != nil {
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return err
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}
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// Limit to max block headers per message.
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if count > MaxBlockHeadersPerMsg {
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str := fmt.Sprintf("too many block headers for message "+
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"[count %v, max %v]", count, MaxBlockHeadersPerMsg)
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return messageError("MsgHeaders.BtcDecode", str)
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}
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// Create a contiguous slice of headers to deserialize into in order to
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// reduce the number of allocations.
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headers := make([]BlockHeader, count)
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msg.Headers = make([]*BlockHeader, 0, count)
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for i := uint64(0); i < count; i++ {
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bh := &headers[i]
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err := readBlockHeader(r, pver, bh)
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if err != nil {
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return err
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}
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txCount, err := ReadVarInt(r, pver)
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if err != nil {
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return err
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}
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// Ensure the transaction count is zero for headers.
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if txCount > 0 {
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str := fmt.Sprintf("block headers may not contain "+
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"transactions [count %v]", txCount)
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return messageError("MsgHeaders.BtcDecode", str)
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}
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msg.AddBlockHeader(bh)
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}
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return nil
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}
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// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
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// This is part of the Message interface implementation.
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func (msg *MsgHeaders) BtcEncode(w io.Writer, pver uint32, enc MessageEncoding) error {
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// Limit to max block headers per message.
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count := len(msg.Headers)
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if count > MaxBlockHeadersPerMsg {
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str := fmt.Sprintf("too many block headers for message "+
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"[count %v, max %v]", count, MaxBlockHeadersPerMsg)
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return messageError("MsgHeaders.BtcEncode", str)
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}
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err := WriteVarInt(w, pver, uint64(count))
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if err != nil {
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return err
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}
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for _, bh := range msg.Headers {
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err := writeBlockHeader(w, pver, bh)
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if err != nil {
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return err
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}
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// The wire protocol encoding always includes a 0 for the number
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// of transactions on header messages. This is really just an
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// artifact of the way the original implementation serializes
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// block headers, but it is required.
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err = WriteVarInt(w, pver, 0)
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if err != nil {
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return err
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}
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}
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return nil
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}
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// Command returns the protocol command string for the message. This is part
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// of the Message interface implementation.
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func (msg *MsgHeaders) Command() string {
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return CmdHeaders
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}
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// MaxPayloadLength returns the maximum length the payload can be for the
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// receiver. This is part of the Message interface implementation.
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func (msg *MsgHeaders) MaxPayloadLength(pver uint32) uint32 {
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// Num headers (varInt) + max allowed headers (header length + 1 byte
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// for the number of transactions which is always 0).
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return MaxVarIntPayload + ((MaxBlockHeaderPayload + 1) *
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MaxBlockHeadersPerMsg)
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}
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// NewMsgHeaders returns a new bitcoin headers message that conforms to the
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// Message interface. See MsgHeaders for details.
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func NewMsgHeaders() *MsgHeaders {
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return &MsgHeaders{
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Headers: make([]*BlockHeader, 0, MaxBlockHeadersPerMsg),
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}
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}
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