249 lines
8.4 KiB
Go
249 lines
8.4 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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"bytes"
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"fmt"
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"io"
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)
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// defaultTransactionAlloc is the default size used for the backing array
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// for transactions. The transaction array will dynamically grow as needed, but
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// this figure is intended to provide enough space for the number of
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// transactions in the vast majority of blocks without needing to grow the
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// backing array multiple times.
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const defaultTransactionAlloc = 2048
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// MaxBlocksPerMsg is the maximum number of blocks allowed per message.
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const MaxBlocksPerMsg = 500
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// MaxBlockPayload is the maximum bytes a block message can be in bytes.
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const MaxBlockPayload = 1000000 // Not actually 1MB which would be 1024 * 1024
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// maxTxPerBlock is the maximum number of transactions that could
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// possibly fit into a block.
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const maxTxPerBlock = (MaxBlockPayload / minTxPayload) + 1
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// TxLoc holds locator data for the offset and length of where a transaction is
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// located within a MsgBlock data buffer.
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type TxLoc struct {
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TxStart int
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TxLen int
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}
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// MsgBlock implements the Message interface and represents a bitcoin
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// block message. It is used to deliver block and transaction information in
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// response to a getdata message (MsgGetData) for a given block hash.
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type MsgBlock struct {
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Header BlockHeader
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Transactions []*MsgTx
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}
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// AddTransaction adds a transaction to the message.
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func (msg *MsgBlock) AddTransaction(tx *MsgTx) error {
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msg.Transactions = append(msg.Transactions, tx)
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return nil
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}
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// ClearTransactions removes all transactions from the message.
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func (msg *MsgBlock) ClearTransactions() {
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msg.Transactions = make([]*MsgTx, 0, defaultTransactionAlloc)
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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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// See Deserialize for decoding blocks stored to disk, such as in a database, as
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// opposed to decoding blocks from the wire.
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func (msg *MsgBlock) BtcDecode(r io.Reader, pver uint32) error {
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err := readBlockHeader(r, pver, &msg.Header)
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if err != nil {
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return err
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}
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txCount, 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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// Prevent more transactions than could possibly fit into a block.
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// It would be possible to cause memory exhaustion and panics without
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// a sane upper bound on this count.
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if txCount > maxTxPerBlock {
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str := fmt.Sprintf("too many transactions to fit into a block "+
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"[count %d, max %d]", txCount, maxTxPerBlock)
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return messageError("MsgBlock.BtcDecode", str)
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}
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msg.Transactions = make([]*MsgTx, 0, txCount)
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for i := uint64(0); i < txCount; i++ {
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tx := MsgTx{}
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err := tx.BtcDecode(r, pver)
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if err != nil {
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return err
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}
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msg.Transactions = append(msg.Transactions, &tx)
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}
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return nil
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}
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// Deserialize decodes a block from r into the receiver using a format that is
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// suitable for long-term storage such as a database while respecting the
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// Version field in the block. This function differs from BtcDecode in that
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// BtcDecode decodes from the bitcoin wire protocol as it was sent across the
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// network. The wire encoding can technically differ depending on the protocol
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// version and doesn't even really need to match the format of a stored block at
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// all. As of the time this comment was written, the encoded block is the same
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// in both instances, but there is a distinct difference and separating the two
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// allows the API to be flexible enough to deal with changes.
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func (msg *MsgBlock) Deserialize(r io.Reader) error {
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// At the current time, there is no difference between the wire encoding
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// at protocol version 0 and the stable long-term storage format. As
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// a result, make use of BtcDecode.
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return msg.BtcDecode(r, 0)
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}
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// DeserializeTxLoc decodes r in the same manner Deserialize does, but it takes
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// a byte buffer instead of a generic reader and returns a slice containing the
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// start and length of each transaction within the raw data that is being
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// deserialized.
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func (msg *MsgBlock) DeserializeTxLoc(r *bytes.Buffer) ([]TxLoc, error) {
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fullLen := r.Len()
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// At the current time, there is no difference between the wire encoding
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// at protocol version 0 and the stable long-term storage format. As
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// a result, make use of existing wire protocol functions.
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err := readBlockHeader(r, 0, &msg.Header)
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if err != nil {
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return nil, err
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}
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txCount, err := readVarInt(r, 0)
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if err != nil {
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return nil, err
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}
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// Prevent more transactions than could possibly fit into a block.
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// It would be possible to cause memory exhaustion and panics without
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// a sane upper bound on this count.
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if txCount > maxTxPerBlock {
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str := fmt.Sprintf("too many transactions to fit into a block "+
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"[count %d, max %d]", txCount, maxTxPerBlock)
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return nil, messageError("MsgBlock.DeserializeTxLoc", str)
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}
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// Deserialize each transaction while keeping track of its location
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// within the byte stream.
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msg.Transactions = make([]*MsgTx, 0, txCount)
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txLocs := make([]TxLoc, txCount)
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for i := uint64(0); i < txCount; i++ {
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txLocs[i].TxStart = fullLen - r.Len()
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tx := MsgTx{}
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err := tx.Deserialize(r)
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if err != nil {
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return nil, err
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}
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msg.Transactions = append(msg.Transactions, &tx)
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txLocs[i].TxLen = (fullLen - r.Len()) - txLocs[i].TxStart
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}
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return txLocs, 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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// See Serialize for encoding blocks to be stored to disk, such as in a
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// database, as opposed to encoding blocks for the wire.
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func (msg *MsgBlock) BtcEncode(w io.Writer, pver uint32) error {
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err := writeBlockHeader(w, pver, &msg.Header)
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if err != nil {
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return err
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}
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err = writeVarInt(w, pver, uint64(len(msg.Transactions)))
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if err != nil {
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return err
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}
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for _, tx := range msg.Transactions {
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err = tx.BtcEncode(w, pver)
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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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// Serialize encodes the block to w using a format that suitable for long-term
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// storage such as a database while respecting the Version field in the block.
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// This function differs from BtcEncode in that BtcEncode encodes the block to
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// the bitcoin wire protocol in order to be sent across the network. The wire
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// encoding can technically differ depending on the protocol version and doesn't
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// even really need to match the format of a stored block at all. As of the
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// time this comment was written, the encoded block is the same in both
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// instances, but there is a distinct difference and separating the two allows
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// the API to be flexible enough to deal with changes.
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func (msg *MsgBlock) Serialize(w io.Writer) error {
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// At the current time, there is no difference between the wire encoding
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// at protocol version 0 and the stable long-term storage format. As
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// a result, make use of BtcEncode.
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return msg.BtcEncode(w, 0)
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}
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// SerializeSize returns the number of bytes it would take to serialize the
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// the block.
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func (msg *MsgBlock) SerializeSize() int {
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// Block header bytes + Serialized varint size for the number of
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// transactions.
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n := blockHeaderLen + VarIntSerializeSize(uint64(len(msg.Transactions)))
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for _, tx := range msg.Transactions {
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n += tx.SerializeSize()
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}
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return n
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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 *MsgBlock) Command() string {
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return CmdBlock
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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 *MsgBlock) MaxPayloadLength(pver uint32) uint32 {
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// Block header at 80 bytes + transaction count + max transactions
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// which can vary up to the MaxBlockPayload (including the block header
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// and transaction count).
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return MaxBlockPayload
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}
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// BlockSha computes the block identifier hash for this block.
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func (msg *MsgBlock) BlockSha() ShaHash {
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return msg.Header.BlockSha()
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}
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// TxShas returns a slice of hashes of all of transactions in this block.
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func (msg *MsgBlock) TxShas() ([]ShaHash, error) {
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shaList := make([]ShaHash, 0, len(msg.Transactions))
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for _, tx := range msg.Transactions {
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shaList = append(shaList, tx.TxSha())
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}
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return shaList, nil
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}
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// NewMsgBlock returns a new bitcoin block message that conforms to the
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// Message interface. See MsgBlock for details.
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func NewMsgBlock(blockHeader *BlockHeader) *MsgBlock {
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return &MsgBlock{
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Header: *blockHeader,
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Transactions: make([]*MsgTx, 0, defaultTransactionAlloc),
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}
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}
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