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msgcfheaders.go
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msgcfheaders.go
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// Copyright (c) 2017 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/lbryio/lbcd/chaincfg/chainhash"
)
const (
// MaxCFHeaderPayload is the maximum byte size of a committed
// filter header.
MaxCFHeaderPayload = chainhash.HashSize
// MaxCFHeadersPerMsg is the maximum number of committed filter headers
// that can be in a single bitcoin cfheaders message.
MaxCFHeadersPerMsg = 2000
)
// MsgCFHeaders implements the Message interface and represents a bitcoin
// cfheaders message. It is used to deliver committed filter header information
// in response to a getcfheaders message (MsgGetCFHeaders). The maximum number
// of committed filter headers per message is currently 2000. See
// MsgGetCFHeaders for details on requesting the headers.
type MsgCFHeaders struct {
FilterType FilterType
StopHash chainhash.Hash
PrevFilterHeader chainhash.Hash
FilterHashes []*chainhash.Hash
}
// AddCFHash adds a new filter hash to the message.
func (msg *MsgCFHeaders) AddCFHash(hash *chainhash.Hash) error {
if len(msg.FilterHashes)+1 > MaxCFHeadersPerMsg {
str := fmt.Sprintf("too many block headers in message [max %v]",
MaxBlockHeadersPerMsg)
return messageError("MsgCFHeaders.AddCFHash", str)
}
msg.FilterHashes = append(msg.FilterHashes, hash)
return nil
}
// BtcDecode decodes r using the bitcoin protocol encoding into the receiver.
// This is part of the Message interface implementation.
func (msg *MsgCFHeaders) BtcDecode(r io.Reader, pver uint32, _ MessageEncoding) error {
// Read filter type
err := readElement(r, &msg.FilterType)
if err != nil {
return err
}
// Read stop hash
err = readElement(r, &msg.StopHash)
if err != nil {
return err
}
// Read prev filter header
err = readElement(r, &msg.PrevFilterHeader)
if err != nil {
return err
}
// Read number of filter headers
count, err := ReadVarInt(r, pver)
if err != nil {
return err
}
// Limit to max committed filter headers per message.
if count > MaxCFHeadersPerMsg {
str := fmt.Sprintf("too many committed filter headers for "+
"message [count %v, max %v]", count,
MaxBlockHeadersPerMsg)
return messageError("MsgCFHeaders.BtcDecode", str)
}
// Create a contiguous slice of hashes to deserialize into in order to
// reduce the number of allocations.
msg.FilterHashes = make([]*chainhash.Hash, 0, count)
for i := uint64(0); i < count; i++ {
var cfh chainhash.Hash
err := readElement(r, &cfh)
if err != nil {
return err
}
msg.AddCFHash(&cfh)
}
return nil
}
// BtcEncode encodes the receiver to w using the bitcoin protocol encoding.
// This is part of the Message interface implementation.
func (msg *MsgCFHeaders) BtcEncode(w io.Writer, pver uint32, _ MessageEncoding) error {
// Write filter type
err := writeElement(w, msg.FilterType)
if err != nil {
return err
}
// Write stop hash
err = writeElement(w, msg.StopHash)
if err != nil {
return err
}
// Write prev filter header
err = writeElement(w, msg.PrevFilterHeader)
if err != nil {
return err
}
// Limit to max committed headers per message.
count := len(msg.FilterHashes)
if count > MaxCFHeadersPerMsg {
str := fmt.Sprintf("too many committed filter headers for "+
"message [count %v, max %v]", count,
MaxBlockHeadersPerMsg)
return messageError("MsgCFHeaders.BtcEncode", str)
}
err = WriteVarInt(w, pver, uint64(count))
if err != nil {
return err
}
for _, cfh := range msg.FilterHashes {
err := writeElement(w, cfh)
if err != nil {
return err
}
}
return nil
}
// Deserialize decodes a filter header from r into the receiver using a format
// that is suitable for long-term storage such as a database. This function
// differs from BtcDecode in that BtcDecode decodes from the bitcoin wire
// protocol as it was sent across the network. The wire encoding can
// technically differ depending on the protocol version and doesn't even really
// need to match the format of a stored filter header at all. As of the time
// this comment was written, the encoded filter header is the same in both
// instances, but there is a distinct difference and separating the two allows
// the API to be flexible enough to deal with changes.
func (msg *MsgCFHeaders) Deserialize(r io.Reader) error {
// At the current time, there is no difference between the wire encoding
// and the stable long-term storage format. As a result, make use of
// BtcDecode.
return msg.BtcDecode(r, 0, BaseEncoding)
}
// Command returns the protocol command string for the message. This is part
// of the Message interface implementation.
func (msg *MsgCFHeaders) Command() string {
return CmdCFHeaders
}
// MaxPayloadLength returns the maximum length the payload can be for the
// receiver. This is part of the Message interface implementation.
func (msg *MsgCFHeaders) MaxPayloadLength(pver uint32) uint32 {
// Hash size + filter type + num headers (varInt) +
// (header size * max headers).
return 1 + chainhash.HashSize + chainhash.HashSize + MaxVarIntPayload +
(MaxCFHeaderPayload * MaxCFHeadersPerMsg)
}
// NewMsgCFHeaders returns a new bitcoin cfheaders message that conforms to
// the Message interface. See MsgCFHeaders for details.
func NewMsgCFHeaders() *MsgCFHeaders {
return &MsgCFHeaders{
FilterHashes: make([]*chainhash.Hash, 0, MaxCFHeadersPerMsg),
}
}