139 lines
4.5 KiB
Go
139 lines
4.5 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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// defaultInvListAlloc is the default size used for the backing array for an
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// inventory list. The array will dynamically grow as needed, but this
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// figure is intended to provide enough space for the max number of inventory
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// vectors in a *typical* inventory message without needing to grow the backing
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// array multiple times. Technically, the list can grow to MaxInvPerMsg, but
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// rather than using that large figure, this figure more accurately reflects the
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// typical case.
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const defaultInvListAlloc = 1000
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// MsgInv implements the Message interface and represents a bitcoin inv message.
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// It is used to advertise a peer's known data such as blocks and transactions
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// through inventory vectors. It may be sent unsolicited to inform other peers
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// of the data or in response to a getblocks message (MsgGetBlocks). Each
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// message is limited to a maximum number of inventory vectors, which is
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// currently 50,000.
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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 an inv message to another peer.
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type MsgInv 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 *MsgInv) 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("MsgInv.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 *MsgInv) 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("MsgInv.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 *MsgInv) 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("MsgInv.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 *MsgInv) Command() string {
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return cmdInv
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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 *MsgInv) 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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// NewMsgInv returns a new bitcoin inv message that conforms to the Message
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// interface. See MsgInv for details.
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func NewMsgInv() *MsgInv {
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return &MsgInv{
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InvList: make([]*InvVect, 0, defaultInvListAlloc),
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}
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}
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// NewMsgInvSizeHint returns a new bitcoin inv message that conforms to the
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// Message interface. See MsgInv for details. This function differs from
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// NewMsgInv in that it allows a default allocation size for the backing array
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// which houses the inventory vector list. This allows callers who know in
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// advance how large the inventory list will grow to avoid the overhead of
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// growing the internal backing array several times when appending large amounts
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// of inventory vectors with AddInvVect. Note that the specified hint is just
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// that - a hint that is used for the default allocation size. Adding more
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// (or less) inventory vectors will still work properly. The size hint is
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// limited to MaxInvPerMsg.
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func NewMsgInvSizeHint(sizeHint uint) *MsgInv {
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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 &MsgInv{
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InvList: make([]*InvVect, 0, sizeHint),
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}
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}
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