package record import ( "fmt" "io" "github.com/lightningnetwork/lnd/tlv" ) // AMPOnionType is the type used in the onion to reference the AMP fields: // root_share, set_id, and child_index. const AMPOnionType tlv.Type = 10 // AMP is a record that encodes the fields necessary for atomic multi-path // payments. type AMP struct { rootShare [32]byte setID [32]byte childIndex uint16 } // NewAMP generate a new AMP record with the given root_share, set_id, and // child_index. func NewAMP(rootShare, setID [32]byte, childIndex uint16) *AMP { return &{ rootShare: rootShare, setID: setID, childIndex: childIndex, } } // RootShare returns the root share contained in the AMP record. func (a *AMP) RootShare() [32]byte { return a.rootShare } // SetID returns the set id contained in the AMP record. func (a *AMP) SetID() [32]byte { return a.setID } // ChildIndex returns the child index contained in the AMP record. func (a *AMP) ChildIndex() uint16 { return a.childIndex } // AMPEncoder writes the AMP record to the provided io.Writer. func AMPEncoder(w io.Writer, val interface{}, buf *[8]byte) error { if v, ok := val.(*AMP); ok { if err := tlv.EBytes32(w, &v.rootShare, buf); err != nil { return err } if err := tlv.EBytes32(w, &v.setID, buf); err != nil { return err } return tlv.ETUint16T(w, v.childIndex, buf) } return tlv.NewTypeForEncodingErr(val, "AMP") } const ( // minAMPLength is the minimum length of a serialized AMP TLV record, // which occurs when the truncated encoding of child_index takes 0 // bytes, leaving only the root_share and set_id. minAMPLength = 64 // maxAMPLength is the maximum legnth of a serialized AMP TLV record, // which occurs when the truncated endoing of a child_index takes 2 // bytes. maxAMPLength = 66 ) // AMPDecoder reads the AMP record from the provided io.Reader. func AMPDecoder(r io.Reader, val interface{}, buf *[8]byte, l uint64) error { if v, ok := val.(*AMP); ok && minAMPLength <= l && l <= maxAMPLength { if err := tlv.DBytes32(r, &v.rootShare, buf, 32); err != nil { return err } if err := tlv.DBytes32(r, &v.setID, buf, 32); err != nil { return err } return tlv.DTUint16(r, &v.childIndex, buf, l-64) } return tlv.NewTypeForDecodingErr(val, "AMP", l, maxAMPLength) } // Record returns a tlv.Record that can be used to encode or decode this record. func (a *AMP) Record() tlv.Record { return tlv.MakeDynamicRecord( AMPOnionType, a, a.PayloadSize, AMPEncoder, AMPDecoder, ) } // PayloadSize returns the size this record takes up in encoded form. func (a *AMP) PayloadSize() uint64 { return 32 + 32 + tlv.SizeTUint16(a.childIndex) } // String returns a human-readble description of the amp payload fields. func (a *AMP) String() string { return fmt.Sprintf("root_share=%x set_id=%x child_index=%d", a.rootShare, a.setID, a.childIndex) }