lnwire21: add custom records parsing

We add the new custom records encoding/decoding logic to the "frozen"
lnwire21 package. We can do this because nothing uses this logic yet. If
the custom records logic changes, the changes should _not_ be added to
the lnwire21 version.

channeldb/migration/lnwire21/custom_records.go

@@ -0,0 +1,263 @@
+package lnwire
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"sort"
+
+	"github.com/lightningnetwork/lnd/fn"
+	"github.com/lightningnetwork/lnd/tlv"
+)
+
+const (
+	// MinCustomRecordsTlvType is the minimum custom records TLV type as
+	// defined in BOLT 01.
+	MinCustomRecordsTlvType = 65536
+)
+
+// CustomRecords stores a set of custom key/value pairs. Map keys are TLV types
+// which must be greater than or equal to MinCustomRecordsTlvType.
+type CustomRecords map[uint64][]byte
+
+// NewCustomRecords creates a new CustomRecords instance from a
+// tlv.TypeMap.
+func NewCustomRecords(tlvMap tlv.TypeMap) (CustomRecords, error) {
+	// Make comparisons in unit tests easy by returning nil if the map is
+	// empty.
+	if len(tlvMap) == 0 {
+		return nil, nil
+	}
+
+	customRecords := make(CustomRecords, len(tlvMap))
+	for k, v := range tlvMap {
+		customRecords[uint64(k)] = v
+	}
+
+	// Validate the custom records.
+	err := customRecords.Validate()
+	if err != nil {
+		return nil, fmt.Errorf("custom records from tlv map "+
+			"validation error: %w", err)
+	}
+
+	return customRecords, nil
+}
+
+// ParseCustomRecords creates a new CustomRecords instance from a tlv.Blob.
+func ParseCustomRecords(b tlv.Blob) (CustomRecords, error) {
+	return ParseCustomRecordsFrom(bytes.NewReader(b))
+}
+
+// ParseCustomRecordsFrom creates a new CustomRecords instance from a reader.
+func ParseCustomRecordsFrom(r io.Reader) (CustomRecords, error) {
+	typeMap, err := DecodeRecords(r)
+	if err != nil {
+		return nil, fmt.Errorf("error decoding HTLC record: %w", err)
+	}
+
+	return NewCustomRecords(typeMap)
+}
+
+// Validate checks that all custom records are in the custom type range.
+func (c CustomRecords) Validate() error {
+	if c == nil {
+		return nil
+	}
+
+	for key := range c {
+		if key < MinCustomRecordsTlvType {
+			return fmt.Errorf("custom records entry with TLV "+
+				"type below min: %d", MinCustomRecordsTlvType)
+		}
+	}
+
+	return nil
+}
+
+// Copy returns a copy of the custom records.
+func (c CustomRecords) Copy() CustomRecords {
+	if c == nil {
+		return nil
+	}
+
+	customRecords := make(CustomRecords, len(c))
+	for k, v := range c {
+		customRecords[k] = v
+	}
+
+	return customRecords
+}
+
+// ExtendRecordProducers extends the given records slice with the custom
+// records. The resultant records slice will be sorted if the given records
+// slice contains TLV types greater than or equal to MinCustomRecordsTlvType.
+func (c CustomRecords) ExtendRecordProducers(
+	producers []tlv.RecordProducer) ([]tlv.RecordProducer, error) {
+
+	// If the custom records are nil or empty, there is nothing to do.
+	if len(c) == 0 {
+		return producers, nil
+	}
+
+	// Validate the custom records.
+	err := c.Validate()
+	if err != nil {
+		return nil, err
+	}
+
+	// Ensure that the existing records slice TLV types are not also present
+	// in the custom records. If they are, the resultant extended records
+	// slice would erroneously contain duplicate TLV types.
+	for _, rp := range producers {
+		record := rp.Record()
+		recordTlvType := uint64(record.Type())
+
+		_, foundDuplicateTlvType := c[recordTlvType]
+		if foundDuplicateTlvType {
+			return nil, fmt.Errorf("custom records contains a TLV "+
+				"type that is already present in the "+
+				"existing records: %d", recordTlvType)
+		}
+	}
+
+	// Convert the custom records map to a TLV record producer slice and
+	// append them to the exiting records slice.
+	customRecordProducers := RecordsAsProducers(tlv.MapToRecords(c))
+	producers = append(producers, customRecordProducers...)
+
+	// If the records slice which was given as an argument included TLV
+	// values greater than or equal to the minimum custom records TLV type
+	// we will sort the extended records slice to ensure that it is ordered
+	// correctly.
+	SortProducers(producers)
+
+	return producers, nil
+}
+
+// RecordProducers returns a slice of record producers for the custom records.
+func (c CustomRecords) RecordProducers() []tlv.RecordProducer {
+	// If the custom records are nil or empty, return an empty slice.
+	if len(c) == 0 {
+		return nil
+	}
+
+	// Convert the custom records map to a TLV record producer slice.
+	records := tlv.MapToRecords(c)
+
+	return RecordsAsProducers(records)
+}
+
+// Serialize serializes the custom records into a byte slice.
+func (c CustomRecords) Serialize() ([]byte, error) {
+	records := tlv.MapToRecords(c)
+	return EncodeRecords(records)
+}
+
+// SerializeTo serializes the custom records into the given writer.
+func (c CustomRecords) SerializeTo(w io.Writer) error {
+	records := tlv.MapToRecords(c)
+	return EncodeRecordsTo(w, records)
+}
+
+// ProduceRecordsSorted converts a slice of record producers into a slice of
+// records and then sorts it by type.
+func ProduceRecordsSorted(recordProducers ...tlv.RecordProducer) []tlv.Record {
+	records := fn.Map(func(producer tlv.RecordProducer) tlv.Record {
+		return producer.Record()
+	}, recordProducers)
+
+	// Ensure that the set of records are sorted before we attempt to
+	// decode from the stream, to ensure they're canonical.
+	tlv.SortRecords(records)
+
+	return records
+}
+
+// SortProducers sorts the given record producers by their type.
+func SortProducers(producers []tlv.RecordProducer) {
+	sort.Slice(producers, func(i, j int) bool {
+		recordI := producers[i].Record()
+		recordJ := producers[j].Record()
+		return recordI.Type() < recordJ.Type()
+	})
+}
+
+// TlvMapToRecords converts a TLV map into a slice of records.
+func TlvMapToRecords(tlvMap tlv.TypeMap) []tlv.Record {
+	tlvMapGeneric := make(map[uint64][]byte)
+	for k, v := range tlvMap {
+		tlvMapGeneric[uint64(k)] = v
+	}
+
+	return tlv.MapToRecords(tlvMapGeneric)
+}
+
+// RecordsAsProducers converts a slice of records into a slice of record
+// producers.
+func RecordsAsProducers(records []tlv.Record) []tlv.RecordProducer {
+	return fn.Map(func(record tlv.Record) tlv.RecordProducer {
+		return &record
+	}, records)
+}
+
+// EncodeRecords encodes the given records into a byte slice.
+func EncodeRecords(records []tlv.Record) ([]byte, error) {
+	var buf bytes.Buffer
+	if err := EncodeRecordsTo(&buf, records); err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
+// EncodeRecordsTo encodes the given records into the given writer.
+func EncodeRecordsTo(w io.Writer, records []tlv.Record) error {
+	tlvStream, err := tlv.NewStream(records...)
+	if err != nil {
+		return err
+	}
+
+	return tlvStream.Encode(w)
+}
+
+// DecodeRecords decodes the given byte slice into the given records and returns
+// the rest as a TLV type map.
+func DecodeRecords(r io.Reader,
+	records ...tlv.Record) (tlv.TypeMap, error) {
+
+	tlvStream, err := tlv.NewStream(records...)
+	if err != nil {
+		return nil, err
+	}
+
+	return tlvStream.DecodeWithParsedTypes(r)
+}
+
+// DecodeRecordsP2P decodes the given byte slice into the given records and
+// returns the rest as a TLV type map. This function is identical to
+// DecodeRecords except that the record size is capped at 65535.
+func DecodeRecordsP2P(r *bytes.Reader,
+	records ...tlv.Record) (tlv.TypeMap, error) {
+
+	tlvStream, err := tlv.NewStream(records...)
+	if err != nil {
+		return nil, err
+	}
+
+	return tlvStream.DecodeWithParsedTypesP2P(r)
+}
+
+// AssertUniqueTypes asserts that the given records have unique types.
+func AssertUniqueTypes(r []tlv.Record) error {
+	seen := make(fn.Set[tlv.Type], len(r))
+	for _, record := range r {
+		t := record.Type()
+		if seen.Contains(t) {
+			return fmt.Errorf("duplicate record type: %d", t)
+		}
+		seen.Add(t)
+	}
+
+	return nil
+}