5f971e10e6
Several of the messages store the parts that have a variable number of elements as slices. This commit modifies the code to choose sane defaults for the backing arrays for the slices so when the entries are actually appended, a lot of the overhead of growing the backing arrays and copying the data multiple times is avoided. Along the same lines, when decoding messages, the actual size is known and now is pre-allocated instead of dynamically growing the backing array thereby avoiding some overhead.
124 lines
3.7 KiB
Go
124 lines
3.7 KiB
Go
// Copyright (c) 2013 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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// MaxBlockHeadersPerMsg is the maximum number of block headers that can be in
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// a single bitcoin headers message.
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const MaxBlockHeadersPerMsg = 2000
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// MsgHeaders implements the Message interface and represents a bitcoin headers
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// message. It is used to deliver block header information in response
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// to a getheaders message (MsgGetHeaders). The maximum number of block headers
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// per message is currently 2000. See MsgGetHeaders for details on requesting
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// the headers.
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type MsgHeaders struct {
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Headers []*BlockHeader
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}
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// AddBlockHeader adds a new block header to the message.
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func (msg *MsgHeaders) AddBlockHeader(bh *BlockHeader) error {
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if len(msg.Headers)+1 > MaxBlockHeadersPerMsg {
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str := fmt.Sprintf("too many block headers in message [max %v]",
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MaxBlockHeadersPerMsg)
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return messageError("MsgHeaders.AddBlockHeader", str)
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}
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msg.Headers = append(msg.Headers, bh)
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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 *MsgHeaders) 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 block headers per message.
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if count > MaxBlockHeadersPerMsg {
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str := fmt.Sprintf("too many block headers for message "+
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"[count %v, max %v]", count, MaxBlockHeadersPerMsg)
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return messageError("MsgHeaders.BtcDecode", str)
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}
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msg.Headers = make([]*BlockHeader, 0, count)
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for i := uint64(0); i < count; i++ {
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bh := BlockHeader{}
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err := readBlockHeader(r, pver, &bh)
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if err != nil {
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return err
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}
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// Ensure the transaction count is zero for headers.
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if bh.TxnCount > 0 {
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str := fmt.Sprintf("block headers may not contain "+
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"transactions [count %v]", bh.TxnCount)
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return messageError("MsgHeaders.BtcDecode", str)
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}
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msg.AddBlockHeader(&bh)
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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 *MsgHeaders) BtcEncode(w io.Writer, pver uint32) error {
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// Limit to max block headers per message.
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count := len(msg.Headers)
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if count > MaxBlockHeadersPerMsg {
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str := fmt.Sprintf("too many block headers for message "+
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"[count %v, max %v]", count, MaxBlockHeadersPerMsg)
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return messageError("MsgHeaders.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 _, bh := range msg.Headers {
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// Ensure block headers do not contain a transaction count.
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if bh.TxnCount > 0 {
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str := fmt.Sprintf("block headers may not contain "+
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"transactions [count %v]", bh.TxnCount)
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return messageError("MsgHeaders.BtcEncode", str)
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}
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err := writeBlockHeader(w, pver, bh)
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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 *MsgHeaders) Command() string {
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return cmdHeaders
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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 *MsgHeaders) MaxPayloadLength(pver uint32) uint32 {
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// Num headers (varInt) + max allowed headers.
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return maxVarIntPayload + (maxBlockHeaderPayload * MaxBlockHeadersPerMsg)
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}
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// NewMsgHeaders returns a new bitcoin headers message that conforms to the
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// Message interface. See MsgHeaders for details.
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func NewMsgHeaders() *MsgHeaders {
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return &MsgHeaders{
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Headers: make([]*BlockHeader, 0, MaxBlockHeadersPerMsg),
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}
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}
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