lnwire: add QueryOptions type

This commit adds a new QueryOptions type which will later be used in the
QueryReplyRange message.

lnwire/query_options.go

@@ -0,0 +1,80 @@
+package lnwire
+
+import (
+	"io"
+
+	"github.com/lightningnetwork/lnd/tlv"
+)
+
+const (
+	// QueryOptionsRecordType is the TLV number of the query_options TLV
+	// record in the query_channel_range message.
+	QueryOptionsRecordType tlv.Type = 1
+
+	// QueryOptionTimestampBit is the bit position in the query_option
+	// feature bit vector which is used to indicate that timestamps are
+	// desired in the reply_channel_range response.
+	QueryOptionTimestampBit = 0
+)
+
+// QueryOptions is the type used to represent the query_options feature bit
+// vector in the query_channel_range message.
+type QueryOptions RawFeatureVector
+
+// NewTimestampQueryOption is a helper constructor used to construct a
+// QueryOption with the timestamp bit set.
+func NewTimestampQueryOption() *QueryOptions {
+	opt := QueryOptions(*NewRawFeatureVector(
+		QueryOptionTimestampBit,
+	))
+
+	return &opt
+}
+
+// featureBitLen calculates and returns the size of the resulting feature bit
+// vector.
+func (c *QueryOptions) featureBitLen() uint64 {
+	fv := RawFeatureVector(*c)
+
+	return uint64(fv.SerializeSize())
+}
+
+// Record constructs a tlv.Record from the QueryOptions to be used in the
+// query_channel_range message.
+func (c *QueryOptions) Record() tlv.Record {
+	return tlv.MakeDynamicRecord(
+		QueryOptionsRecordType, c, c.featureBitLen, queryOptionsEncoder,
+		queryOptionsDecoder,
+	)
+}
+
+// queryOptionsEncoder encodes the QueryOptions and writes it to the provided
+// writer.
+func queryOptionsEncoder(w io.Writer, val interface{}, _ *[8]byte) error {
+	if v, ok := val.(*QueryOptions); ok {
+		// Encode the feature bits as a byte slice without its length
+		// prepended, as that's already taken care of by the TLV record.
+		fv := RawFeatureVector(*v)
+		return fv.encode(w, fv.SerializeSize(), 8)
+	}
+
+	return tlv.NewTypeForEncodingErr(val, "lnwire.QueryOptions")
+}
+
+// queryOptionsDecoder attempts to read a QueryOptions from the given reader.
+func queryOptionsDecoder(r io.Reader, val interface{}, _ *[8]byte,
+	l uint64) error {
+
+	if v, ok := val.(*QueryOptions); ok {
+		fv := NewRawFeatureVector()
+		if err := fv.decode(r, int(l), 8); err != nil {
+			return err
+		}
+
+		*v = QueryOptions(*fv)
+
+		return nil
+	}
+
+	return tlv.NewTypeForEncodingErr(val, "lnwire.QueryOptions")
+}