134 lines
4.4 KiB
Go
134 lines
4.4 KiB
Go
// Copyright (c) 2013-2015 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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// 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, 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 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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// Create a contiguous slice of inventory vectors to deserialize into in
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// order to reduce the number of allocations.
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invList := make([]InvVect, count)
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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 := &invList[i]
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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, enc MessageEncoding) 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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