lnwire: add type CustomRecords

This commit introduces the `CustomRecords` type in the `lnwire` package,
designed to hold arbitrary byte slices. Each entry in this map can
associate with TLV type values that are greater than or equal to 65536.

lnwire/custom_records.go

@@ -0,0 +1,119 @@
+package lnwire
+
+import (
+	"fmt"
+	"sort"
+
+	"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
+
+// NewCustomRecordsFromTlvTypeMap creates a new CustomRecords instance from a
+// tlv.TypeMap.
+func NewCustomRecordsFromTlvTypeMap(tlvMap tlv.TypeMap) (*CustomRecords,
+	error) {
+
+	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: %v", err)
+	}
+
+	return &customRecords, nil
+}
+
+// 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
+}
+
+// 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(
+	records []tlv.RecordProducer) ([]tlv.RecordProducer, error) {
+
+	// If the custom records are nil or empty, there is nothing to do.
+	if c == nil || len(*c) == 0 {
+		return records, nil
+	}
+
+	// Validate the custom records.
+	err := c.Validate()
+	if err != nil {
+		return nil, err
+	}
+
+	// Keep track of the maximum record TLV type in the given records
+	// slice. This will be used to determine whether the extended records
+	// slice requires sorting.
+	maxRecordTlvType := uint64(0)
+
+	// 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 _, recordProducer := range records {
+		record := recordProducer.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)
+		}
+
+		// Keep track of the maximum record TLV type.
+		if recordTlvType > maxRecordTlvType {
+			maxRecordTlvType = recordTlvType
+		}
+	}
+
+	// Convert the custom records map to a TLV record producer slice and
+	// append them to the exiting records slice.
+	crRecords := tlv.MapToRecords(*c)
+	for _, record := range crRecords {
+		r := recordProducer{record}
+		records = append(records, &r)
+	}
+
+	// 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.
+	if maxRecordTlvType >= MinCustomRecordsTlvType {
+		sort.Slice(records, func(i, j int) bool {
+			recordI := records[i].Record()
+			recordJ := records[j].Record()
+			return recordI.Type() < recordJ.Type()
+		})
+	}
+
+	return records, nil
+}

lnwire/encoding.go

@@ -1,5 +1,7 @@
 package lnwire
 
+import "github.com/lightningnetwork/lnd/tlv"
+
 // QueryEncoding is an enum-like type that represents exactly how a set data is
 // encoded on the wire.
 type QueryEncoding uint8
@@ -15,3 +17,17 @@ const (
 	// NOTE: this should no longer be used or accepted.
 	EncodingSortedZlib QueryEncoding = 1
 )
+
+// recordProducer is a simple helper struct that implements the
+// tlv.RecordProducer interface.
+type recordProducer struct {
+	record tlv.Record
+}
+
+// Record returns the underlying record.
+func (r *recordProducer) Record() tlv.Record {
+	return r.record
+}
+
+// Ensure that recordProducer implements the tlv.RecordProducer interface.
+var _ tlv.RecordProducer = (*recordProducer)(nil)