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msgcfcheckpt.go
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/
msgcfcheckpt.go
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// Copyright (c) 2018 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 (
"errors"
"fmt"
"io"
"github.com/gcash/bchd/chaincfg/chainhash"
)
const (
// CFCheckptInterval is the gap (in number of blocks) between each
// filter header checkpoint.
CFCheckptInterval = 1000
// maxCFHeadersLen is the max number of filter headers we will attempt
// to decode.
maxCFHeadersLen = 100000
)
// ErrInsaneCFHeaderCount signals that we were asked to decode an
// unreasonable number of cfilter headers.
var ErrInsaneCFHeaderCount = errors.New(
"refusing to decode unreasonable number of filter headers")
// MsgCFCheckpt implements the Message interface and represents a bitcoin
// cfcheckpt message. It is used to deliver committed filter header information
// in response to a getcfcheckpt message (MsgGetCFCheckpt). See MsgGetCFCheckpt
// for details on requesting the headers.
type MsgCFCheckpt struct {
FilterType FilterType
StopHash chainhash.Hash
FilterHeaders []*chainhash.Hash
}
// AddCFHeader adds a new committed filter header to the message.
func (msg *MsgCFCheckpt) AddCFHeader(header *chainhash.Hash) error {
if len(msg.FilterHeaders) == cap(msg.FilterHeaders) {
str := fmt.Sprintf("FilterHeaders has insufficient capacity for "+
"additional header: len = %d", len(msg.FilterHeaders))
return messageError("MsgCFCheckpt.AddCFHeader", str)
}
msg.FilterHeaders = append(msg.FilterHeaders, header)
return nil
}
// BchDecode decodes r using the bitcoin protocol encoding into the receiver.
// This is part of the Message interface implementation.
func (msg *MsgCFCheckpt) BchDecode(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 number of filter headers
count, err := ReadVarInt(r, pver)
if err != nil {
return err
}
// Refuse to decode an insane number of cfheaders.
if count > maxCFHeadersLen {
return ErrInsaneCFHeaderCount
}
// Create a contiguous slice of hashes to deserialize into in order to
// reduce the number of allocations.
msg.FilterHeaders = make([]*chainhash.Hash, count)
for i := uint64(0); i < count; i++ {
var cfh chainhash.Hash
err := readElement(r, &cfh)
if err != nil {
return err
}
msg.FilterHeaders[i] = &cfh
}
return nil
}
// BchEncode encodes the receiver to w using the bitcoin protocol encoding.
// This is part of the Message interface implementation.
func (msg *MsgCFCheckpt) BchEncode(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 length of FilterHeaders slice
count := len(msg.FilterHeaders)
err = WriteVarInt(w, pver, uint64(count))
if err != nil {
return err
}
for _, cfh := range msg.FilterHeaders {
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 BchDecode in that BchDecode 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 *MsgCFCheckpt) 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
// BchDecode.
return msg.BchDecode(r, 0, BaseEncoding)
}
// Command returns the protocol command string for the message. This is part
// of the Message interface implementation.
func (msg *MsgCFCheckpt) Command() string {
return CmdCFCheckpt
}
// MaxPayloadLength returns the maximum length the payload can be for the
// receiver. This is part of the Message interface implementation.
func (msg *MsgCFCheckpt) MaxPayloadLength(pver uint32) uint32 {
// Message size depends on the blockchain height, so return general limit
// for all messages.
return maxMessagePayload()
}
// NewMsgCFCheckpt returns a new bitcoin cfheaders message that conforms to
// the Message interface. See MsgCFCheckpt for details.
func NewMsgCFCheckpt(filterType FilterType, stopHash *chainhash.Hash,
headersCount int) *MsgCFCheckpt {
return &MsgCFCheckpt{
FilterType: filterType,
StopHash: *stopHash,
FilterHeaders: make([]*chainhash.Hash, 0, headersCount),
}
}