+++ /dev/null
-// Copyright (c) 2013-2016 The btcsuite developers
-// Use of this source code is governed by an ISC
-// license that can be found in the LICENSE file.
-
-package wire
-
-import (
- "fmt"
- "io"
-
- "github.com/btcsuite/btcd/chaincfg/chainhash"
-)
-
-// MsgGetHeaders implements the Message interface and represents a bitcoin
-// getheaders message. It is used to request a list of block headers for
-// blocks starting after the last known hash in the slice of block locator
-// hashes. The list is returned via a headers message (MsgHeaders) and is
-// limited by a specific hash to stop at or the maximum number of block headers
-// per message, which is currently 2000.
-//
-// Set the HashStop field to the hash at which to stop and use
-// AddBlockLocatorHash to build up the list of block locator hashes.
-//
-// The algorithm for building the block locator hashes should be to add the
-// hashes in reverse order until you reach the genesis block. In order to keep
-// the list of locator hashes to a resonable number of entries, first add the
-// most recent 10 block hashes, then double the step each loop iteration to
-// exponentially decrease the number of hashes the further away from head and
-// closer to the genesis block you get.
-type MsgGetHeaders struct {
- ProtocolVersion uint32
- BlockLocatorHashes []*chainhash.Hash
- HashStop chainhash.Hash
-}
-
-// AddBlockLocatorHash adds a new block locator hash to the message.
-func (msg *MsgGetHeaders) AddBlockLocatorHash(hash *chainhash.Hash) error {
- if len(msg.BlockLocatorHashes)+1 > MaxBlockLocatorsPerMsg {
- str := fmt.Sprintf("too many block locator hashes for message [max %v]",
- MaxBlockLocatorsPerMsg)
- return messageError("MsgGetHeaders.AddBlockLocatorHash", str)
- }
-
- msg.BlockLocatorHashes = append(msg.BlockLocatorHashes, hash)
- return nil
-}
-
-// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
-// This is part of the Message interface implementation.
-func (msg *MsgGetHeaders) BtcDecode(r io.Reader, pver uint32, enc MessageEncoding) error {
- err := readElement(r, &msg.ProtocolVersion)
- if err != nil {
- return err
- }
-
- // Read num block locator hashes and limit to max.
- count, err := ReadVarInt(r, pver)
- if err != nil {
- return err
- }
- if count > MaxBlockLocatorsPerMsg {
- str := fmt.Sprintf("too many block locator hashes for message "+
- "[count %v, max %v]", count, MaxBlockLocatorsPerMsg)
- return messageError("MsgGetHeaders.BtcDecode", str)
- }
-
- // Create a contiguous slice of hashes to deserialize into in order to
- // reduce the number of allocations.
- locatorHashes := make([]chainhash.Hash, count)
- msg.BlockLocatorHashes = make([]*chainhash.Hash, 0, count)
- for i := uint64(0); i < count; i++ {
- hash := &locatorHashes[i]
- err := readElement(r, hash)
- if err != nil {
- return err
- }
- msg.AddBlockLocatorHash(hash)
- }
-
- return readElement(r, &msg.HashStop)
-}
-
-// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
-// This is part of the Message interface implementation.
-func (msg *MsgGetHeaders) BtcEncode(w io.Writer, pver uint32, enc MessageEncoding) error {
- // Limit to max block locator hashes per message.
- count := len(msg.BlockLocatorHashes)
- if count > MaxBlockLocatorsPerMsg {
- str := fmt.Sprintf("too many block locator hashes for message "+
- "[count %v, max %v]", count, MaxBlockLocatorsPerMsg)
- return messageError("MsgGetHeaders.BtcEncode", str)
- }
-
- err := writeElement(w, msg.ProtocolVersion)
- if err != nil {
- return err
- }
-
- err = WriteVarInt(w, pver, uint64(count))
- if err != nil {
- return err
- }
-
- for _, hash := range msg.BlockLocatorHashes {
- err := writeElement(w, hash)
- if err != nil {
- return err
- }
- }
-
- return writeElement(w, &msg.HashStop)
-}
-
-// Command returns the protocol command string for the message. This is part
-// of the Message interface implementation.
-func (msg *MsgGetHeaders) Command() string {
- return CmdGetHeaders
-}
-
-// MaxPayloadLength returns the maximum length the payload can be for the
-// receiver. This is part of the Message interface implementation.
-func (msg *MsgGetHeaders) MaxPayloadLength(pver uint32) uint32 {
- // Version 4 bytes + num block locator hashes (varInt) + max allowed block
- // locators + hash stop.
- return 4 + MaxVarIntPayload + (MaxBlockLocatorsPerMsg *
- chainhash.HashSize) + chainhash.HashSize
-}
-
-// NewMsgGetHeaders returns a new bitcoin getheaders message that conforms to
-// the Message interface. See MsgGetHeaders for details.
-func NewMsgGetHeaders() *MsgGetHeaders {
- return &MsgGetHeaders{
- BlockLocatorHashes: make([]*chainhash.Hash, 0,
- MaxBlockLocatorsPerMsg),
- }
-}
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