lbcd/msginv.go

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2014-01-09 06:44:08 +01:00
// Copyright (c) 2013-2014 Conformal Systems LLC.
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// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package btcwire
import (
"fmt"
"io"
)
// defaultInvListAlloc is the default size used for the backing array for an
// inventory list. The array will dynamically grow as needed, but this
// figure is intended to provide enough space for the max number of inventory
// vectors in a *typical* inventory message without needing to grow the backing
// array multiple times. Technically, the list can grow to MaxInvPerMsg, but
// rather than using that large figure, this figure more accurately reflects the
// typical case.
const defaultInvListAlloc = 1000
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// MsgInv implements the Message interface and represents a bitcoin inv message.
// It is used to advertise a peer's known data such as blocks and transactions
// through inventory vectors. It may be sent unsolicited to inform other peers
// of the data or in response to a getblocks message (MsgGetBlocks). Each
// message is limited to a maximum number of inventory vectors, which is
// currently 50,000.
//
// Use the AddInvVect function to build up the list of inventory vectors when
// sending an inv message to another peer.
type MsgInv struct {
InvList []*InvVect
}
// AddInvVect adds an inventory vector to the message.
func (msg *MsgInv) AddInvVect(iv *InvVect) error {
if len(msg.InvList)+1 > MaxInvPerMsg {
str := fmt.Sprintf("too many invvect in message [max %v]",
MaxInvPerMsg)
return messageError("MsgInv.AddInvVect", str)
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}
msg.InvList = append(msg.InvList, iv)
return nil
}
// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
// This is part of the Message interface implementation.
func (msg *MsgInv) BtcDecode(r io.Reader, pver uint32) error {
count, err := readVarInt(r, pver)
if err != nil {
return err
}
// Limit to max inventory vectors per message.
if count > MaxInvPerMsg {
str := fmt.Sprintf("too many invvect in message [%v]", count)
return messageError("MsgInv.BtcDecode", str)
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}
msg.InvList = make([]*InvVect, 0, count)
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for i := uint64(0); i < count; i++ {
iv := InvVect{}
err := readInvVect(r, pver, &iv)
if err != nil {
return err
}
msg.AddInvVect(&iv)
}
return nil
}
// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
// This is part of the Message interface implementation.
func (msg *MsgInv) BtcEncode(w io.Writer, pver uint32) error {
// Limit to max inventory vectors per message.
count := len(msg.InvList)
if count > MaxInvPerMsg {
str := fmt.Sprintf("too many invvect in message [%v]", count)
return messageError("MsgInv.BtcEncode", str)
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}
err := writeVarInt(w, pver, uint64(count))
if err != nil {
return err
}
for _, iv := range msg.InvList {
err := writeInvVect(w, pver, iv)
if err != nil {
return err
}
}
return nil
}
// Command returns the protocol command string for the message. This is part
// of the Message interface implementation.
func (msg *MsgInv) Command() string {
return cmdInv
}
// MaxPayloadLength returns the maximum length the payload can be for the
// receiver. This is part of the Message interface implementation.
func (msg *MsgInv) MaxPayloadLength(pver uint32) uint32 {
// Num inventory vectors (varInt) + max allowed inventory vectors.
return maxVarIntPayload + (MaxInvPerMsg * maxInvVectPayload)
}
// NewMsgInv returns a new bitcoin inv message that conforms to the Message
// interface. See MsgInv for details.
func NewMsgInv() *MsgInv {
return &MsgInv{
InvList: make([]*InvVect, 0, defaultInvListAlloc),
}
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}
// NewMsgInvSizeHint returns a new bitcoin inv message that conforms to the
// Message interface. See MsgInv for details. This function differs from
// NewMsgInv in that it allows a default allocation size for the backing array
// which houses the inventory vector list. This allows callers who know in
// advance how large the inventory list will grow to avoid the overhead of
// growing the internal backing array several times when appending large amounts
// of inventory vectors with AddInvVect. Note that the specified hint is just
// that - a hint that is used for the default allocation size. Adding more
// (or less) inventory vectors will still work properly. The size hint is
// limited to MaxInvPerMsg.
func NewMsgInvSizeHint(sizeHint uint) *MsgInv {
// Limit the specified hint to the maximum allow per message.
if sizeHint > MaxInvPerMsg {
sizeHint = MaxInvPerMsg
}
return &MsgInv{
InvList: make([]*InvVect, 0, sizeHint),
}
}