lbcd/msgblock.go

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2013-05-08 21:31:00 +02:00
// Copyright (c) 2013 Conformal Systems LLC.
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package btcwire
import (
"bytes"
"io"
)
// MaxBlocksPerMsg is the maximum number of blocks allowed per message.
const MaxBlocksPerMsg = 500
// TxLoc holds locator data for the offset and length of where a transaction is
// located within a MsgBlock data buffer.
type TxLoc struct {
TxStart int
TxLen int
}
// MsgBlock implements the Message interface and represents a bitcoin
// block message. It is used to deliver block and transaction information in
// response to a getdata message (MsgGetData) for a given block hash.
//
// NOTE: Unlike the other message types which contain slices, the number of
// transactions has a specific entry (Header.TxnCount) that must be kept in
// sync. The AddTransaction and ClearTransactions functions properly sync the
// value, but if you are manually modifying the public members, you will need
// to ensure you update the Header.TxnCount when you add and remove
// transactions.
type MsgBlock struct {
Header BlockHeader
Transactions []*MsgTx
}
// AddTransaction adds a transaction to the message and updates Header.TxnCount
// accordingly.
func (msg *MsgBlock) AddTransaction(tx *MsgTx) error {
// TODO: Return error if adding the transaction would make the message
// too large.
msg.Transactions = append(msg.Transactions, tx)
msg.Header.TxnCount = uint64(len(msg.Transactions))
return nil
}
// ClearTransactions removes all transactions from the message and updates
// Header.TxnCount accordingly.
func (msg *MsgBlock) ClearTransactions() {
msg.Transactions = []*MsgTx{}
msg.Header.TxnCount = 0
}
// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
// This is part of the Message interface implementation.
func (msg *MsgBlock) BtcDecode(r io.Reader, pver uint32) error {
err := readBlockHeader(r, pver, &msg.Header)
if err != nil {
return err
}
for i := uint64(0); i < msg.Header.TxnCount; i++ {
tx := MsgTx{}
err := tx.BtcDecode(r, pver)
if err != nil {
return err
}
msg.Transactions = append(msg.Transactions, &tx)
}
return nil
}
// BtcDecodeTxLoc decodes r using the bitcoin protocol encoding into the
// receiver and returns a slice containing the start and length each transaction
// within the raw data.
func (msg *MsgBlock) BtcDecodeTxLoc(r *bytes.Buffer, pver uint32) ([]TxLoc, error) {
var fullLen int
fullLen = r.Len()
err := readBlockHeader(r, pver, &msg.Header)
if err != nil {
return nil, err
}
var txLocs []TxLoc
txLocs = make([]TxLoc, msg.Header.TxnCount)
for i := uint64(0); i < msg.Header.TxnCount; i++ {
txLocs[i].TxStart = fullLen - r.Len()
tx := MsgTx{}
err := tx.BtcDecode(r, pver)
if err != nil {
return nil, err
}
msg.Transactions = append(msg.Transactions, &tx)
txLocs[i].TxLen = (fullLen - r.Len()) - txLocs[i].TxStart
}
return txLocs, nil
}
// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
// This is part of the Message interface implementation.
func (msg *MsgBlock) BtcEncode(w io.Writer, pver uint32) error {
msg.Header.TxnCount = uint64(len(msg.Transactions))
err := writeBlockHeader(w, pver, &msg.Header)
if err != nil {
return err
}
for _, tx := range msg.Transactions {
err = tx.BtcEncode(w, pver)
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 *MsgBlock) Command() string {
return cmdBlock
}
// MaxPayloadLength returns the maximum length the payload can be for the
// receiver. This is part of the Message interface implementation.
func (msg *MsgBlock) MaxPayloadLength(pver uint32) uint32 {
// Block header at 81 bytes + max transactions which can vary up to the
// max message payload.
return maxMessagePayload
}
// BlockSha computes the block identifier hash for this block.
func (msg *MsgBlock) BlockSha(pver uint32) (ShaHash, error) {
return msg.Header.BlockSha(pver)
}
// TxShas returns a slice of hashes of all of transactions in this block.
func (msg *MsgBlock) TxShas(pver uint32) ([]ShaHash, error) {
var shaList []ShaHash
for _, tx := range msg.Transactions {
sha, err := tx.TxSha(pver)
if err != nil {
return nil, err
}
shaList = append(shaList, sha)
}
return shaList, nil
}
// NewMsgBlock returns a new bitcoin block message that conforms to the
// Message interface. See MsgBlock for details.
func NewMsgBlock(blockHeader *BlockHeader) *MsgBlock {
return &MsgBlock{
Header: *blockHeader,
}
}