4deb922c9d
Although it is possible to get the command name for each msg type by creating an instances of the type and calling the Command method against it, it's slightly more efficient to simply allows callers to have direct access to the exported constants. This is currently really useful for the reject message since callers need to be able to examine the command type to determine whether or not the hash field needs to be included.
135 lines
3.9 KiB
Go
135 lines
3.9 KiB
Go
// Copyright (c) 2013-2014 Conformal Systems LLC.
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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 btcwire
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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) 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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msg.Headers = make([]*BlockHeader, 0, count)
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for i := uint64(0); i < count; i++ {
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bh := BlockHeader{}
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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) 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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