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.
130 lines
4.2 KiB
Go
130 lines
4.2 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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// MsgGetData implements the Message interface and represents a bitcoin
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// getdata message. It is used to request data such as blocks and transactions
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// from another peer. It should be used in response to the inv (MsgInv) message
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// to request the actual data referenced by each inventory vector the receiving
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// peer doesn't already have. Each message is limited to a maximum number of
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// inventory vectors, which is currently 50,000. As a result, multiple messages
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// must be used to request larger amounts of data.
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//
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// Use the AddInvVect function to build up the list of inventory vectors when
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// sending a getdata message to another peer.
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type MsgGetData struct {
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InvList []*InvVect
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}
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// AddInvVect adds an inventory vector to the message.
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func (msg *MsgGetData) AddInvVect(iv *InvVect) error {
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if len(msg.InvList)+1 > MaxInvPerMsg {
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str := fmt.Sprintf("too many invvect in message [max %v]",
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MaxInvPerMsg)
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return messageError("MsgGetData.AddInvVect", str)
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}
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msg.InvList = append(msg.InvList, iv)
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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 *MsgGetData) 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 inventory vectors per message.
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if count > MaxInvPerMsg {
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str := fmt.Sprintf("too many invvect in message [%v]", count)
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return messageError("MsgGetData.BtcDecode", str)
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}
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msg.InvList = make([]*InvVect, 0, count)
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for i := uint64(0); i < count; i++ {
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iv := InvVect{}
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err := readInvVect(r, pver, &iv)
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if err != nil {
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return err
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}
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msg.AddInvVect(&iv)
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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 *MsgGetData) BtcEncode(w io.Writer, pver uint32) error {
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// Limit to max inventory vectors per message.
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count := len(msg.InvList)
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if count > MaxInvPerMsg {
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str := fmt.Sprintf("too many invvect in message [%v]", count)
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return messageError("MsgGetData.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 _, iv := range msg.InvList {
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err := writeInvVect(w, pver, iv)
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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 *MsgGetData) Command() string {
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return CmdGetData
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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 *MsgGetData) MaxPayloadLength(pver uint32) uint32 {
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// Num inventory vectors (varInt) + max allowed inventory vectors.
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return MaxVarIntPayload + (MaxInvPerMsg * maxInvVectPayload)
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}
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// NewMsgGetData returns a new bitcoin getdata message that conforms to the
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// Message interface. See MsgGetData for details.
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func NewMsgGetData() *MsgGetData {
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return &MsgGetData{
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InvList: make([]*InvVect, 0, defaultInvListAlloc),
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}
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}
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// NewMsgGetDataSizeHint returns a new bitcoin getdata message that conforms to
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// the Message interface. See MsgGetData for details. This function differs
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// from NewMsgGetData in that it allows a default allocation size for the
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// backing array which houses the inventory vector list. This allows callers
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// who know in advance how large the inventory list will grow to avoid the
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// overhead of growing the internal backing array several times when appending
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// large amounts of inventory vectors with AddInvVect. Note that the specified
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// hint is just that - a hint that is used for the default allocation size.
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// Adding more (or less) inventory vectors will still work properly. The size
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// hint is limited to MaxInvPerMsg.
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func NewMsgGetDataSizeHint(sizeHint uint) *MsgGetData {
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// Limit the specified hint to the maximum allow per message.
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if sizeHint > MaxInvPerMsg {
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sizeHint = MaxInvPerMsg
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}
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return &MsgGetData{
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InvList: make([]*InvVect, 0, sizeHint),
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}
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}
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