lnd.xprv/lnwire/query_short_chan_ids.go
2018-05-31 16:30:50 -07:00

234 lines
7.7 KiB
Go

package lnwire
import (
"bytes"
"fmt"
"io"
"sort"
"github.com/roasbeef/btcd/chaincfg/chainhash"
)
// ShortChanIDEncoding is an enum-like type that represents exactly how a set
// of short channel ID's is encoded on the wire. The set of encodings allows us
// to take advantage of the structure of a list of short channel ID's to
// achieving a high degree of compression.
type ShortChanIDEncoding uint8
const (
// EncodingSortedPlain signals that the set of short channel ID's is
// encoded using the regular encoding, in a sorted order.
EncodingSortedPlain ShortChanIDEncoding = 0
// TODO(roasbeef): list max number of short chan id's that are able to
// use
)
// ErrUnknownShortChanIDEncoding is a parametrized error that indicates that we
// came across an unknown short channel ID encoding, and therefore were unable
// to continue parsing.
func ErrUnknownShortChanIDEncoding(encoding ShortChanIDEncoding) error {
return fmt.Errorf("unknown short chan id encoding: %v", encoding)
}
// QueryShortChanIDs is a message that allows the sender to query a set of
// channel announcement and channel update messages that correspond to the set
// of encoded short channel ID's. The encoding of the short channel ID's is
// detailed in the query message ensuring that the receiver knows how to
// properly decode each encode short channel ID which may be encoded using a
// compression format. The receiver should respond with a series of channel
// announcement and channel updates, finally sending a ReplyShortChanIDsEnd
// message.
type QueryShortChanIDs struct {
// ChainHash denotes the target chain that we're querying for the
// channel channel ID's of.
ChainHash chainhash.Hash
// EncodingType is a signal to the receiver of the message that
// indicates exactly how the set of short channel ID's that follow have
// been encoded.
EncodingType ShortChanIDEncoding
// ShortChanIDs is a slice of decoded short channel ID's.
ShortChanIDs []ShortChannelID
}
// NewQueryShortChanIDs creates a new QueryShortChanIDs message.
func NewQueryShortChanIDs(h chainhash.Hash, e ShortChanIDEncoding,
s []ShortChannelID) *QueryShortChanIDs {
return &QueryShortChanIDs{
ChainHash: h,
EncodingType: e,
ShortChanIDs: s,
}
}
// A compile time check to ensure QueryShortChanIDs implements the
// lnwire.Message interface.
var _ Message = (*QueryShortChanIDs)(nil)
// Decode deserializes a serialized QueryShortChanIDs message stored in the
// passed io.Reader observing the specified protocol version.
//
// This is part of the lnwire.Message interface.
func (q *QueryShortChanIDs) Decode(r io.Reader, pver uint32) error {
err := readElements(r, q.ChainHash[:])
if err != nil {
return err
}
q.EncodingType, q.ShortChanIDs, err = decodeShortChanIDs(r)
return err
}
// decodeShortChanIDs decodes a set of short channel ID's that have been
// encoded. The first byte of the body details how the short chan ID's were
// encoded. We'll use this type to govern exactly how we go about encoding the
// set of short channel ID's.
func decodeShortChanIDs(r io.Reader) (ShortChanIDEncoding, []ShortChannelID, error) {
// First, we'll attempt to read the number of bytes in the body of the
// set of encoded short channel ID's.
var numBytesResp uint16
err := readElements(r, &numBytesResp)
if err != nil {
return 0, nil, err
}
queryBody := make([]byte, numBytesResp)
if _, err := io.ReadFull(r, queryBody); err != nil {
return 0, nil, err
}
// The first byte is the encoding type, so we'll extract that so we can
// continue our parsing.
encodingType := ShortChanIDEncoding(queryBody[0])
// Before continuing, we'll snip off the first byte of the query body
// as that was just the encoding type.
queryBody = queryBody[1:]
// If after extracting the encoding type, then number of remaining
// bytes instead a whole multiple of the size of an encoded short
// channel ID (8 bytes), then we'll return a parsing error.
if len(queryBody)%8 != 0 {
return 0, nil, fmt.Errorf("whole number of short chan ID's "+
"cannot be encoded in len=%v", len(queryBody))
}
// Otherwise, depending on the encoding type, we'll decode the encode
// short channel ID's in a different manner.
switch encodingType {
// In this encoding, we'll simply read a sort array of encoded short
// channel ID's from the buffer.
case EncodingSortedPlain:
// As each short channel ID is encoded as 8 bytes, we can
// compute the number of bytes encoded based on the size of the
// query body.
numShortChanIDs := len(queryBody) / 8
shortChanIDs := make([]ShortChannelID, numShortChanIDs)
// Finally, we'll read out the exact number of short channel
// ID's to conclude our parsing.
bodyReader := bytes.NewReader(queryBody)
for i := 0; i < numShortChanIDs; i++ {
if err := readElements(bodyReader, &shortChanIDs[i]); err != nil {
return 0, nil, fmt.Errorf("unable to parse "+
"short chan ID: %v", err)
}
}
return encodingType, shortChanIDs, nil
default:
// If we've been sent an encoding type that we don't know of,
// then we'll return a parsing error as we can't continue if
// we're unable to encode them.
return 0, nil, ErrUnknownShortChanIDEncoding(encodingType)
}
}
// Encode serializes the target QueryShortChanIDs into the passed io.Writer
// observing the protocol version specified.
//
// This is part of the lnwire.Message interface.
func (q *QueryShortChanIDs) Encode(w io.Writer, pver uint32) error {
// First, we'll write out the chain hash.
err := writeElements(w, q.ChainHash[:])
if err != nil {
return err
}
// Base on our encoding type, we'll write out the set of short channel
// ID's.
return encodeShortChanIDs(w, q.EncodingType, q.ShortChanIDs)
}
// encodeShortChanIDs encodes the passed short channel ID's into the passed
// io.Writer, respecting the specified encoding type.
func encodeShortChanIDs(w io.Writer, encodingType ShortChanIDEncoding,
shortChanIDs []ShortChannelID) error {
switch encodingType {
// In this encoding, we'll simply write a sorted array of encoded short
// channel ID's from the buffer.
case EncodingSortedPlain:
// First, we'll write out the number of bytes of the query
// body. We add 1 as the response will have the encoding type
// prepended to it.
numBytesBody := uint16(len(shortChanIDs)*8) + 1
if err := writeElements(w, numBytesBody); err != nil {
return err
}
// We'll then write out the encoding that that follows the
// actual encoded short channel ID's.
if err := writeElements(w, encodingType); err != nil {
return err
}
// Next, we'll ensure that the set of short channel ID's is
// properly sorted in place.
sort.Slice(shortChanIDs, func(i, j int) bool {
return shortChanIDs[i].ToUint64() <
shortChanIDs[j].ToUint64()
})
// Now that we know they're sorted, we can write out each short
// channel ID to the buffer.
for _, chanID := range shortChanIDs {
if err := writeElements(w, chanID); err != nil {
return fmt.Errorf("unable to write short chan "+
"ID: %v", err)
}
}
return nil
default:
// If we're trying to encode with an encoding type that we
// don't know of, then we'll return a parsing error as we can't
// continue if we're unable to encode them.
return ErrUnknownShortChanIDEncoding(encodingType)
}
}
// MsgType returns the integer uniquely identifying this message type on the
// wire.
//
// This is part of the lnwire.Message interface.
func (q *QueryShortChanIDs) MsgType() MessageType {
return MsgQueryShortChanIDs
}
// MaxPayloadLength returns the maximum allowed payload size for a
// QueryShortChanIDs complete message observing the specified protocol version.
//
// This is part of the lnwire.Message interface.
func (q *QueryShortChanIDs) MaxPayloadLength(uint32) uint32 {
return MaxMessagePayload
}