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108 lines
2.8 KiB
Go
108 lines
2.8 KiB
Go
package record
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import (
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"fmt"
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"io"
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"github.com/lightningnetwork/lnd/tlv"
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)
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// AMPOnionType is the type used in the onion to reference the AMP fields:
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// root_share, set_id, and child_index.
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const AMPOnionType tlv.Type = 14
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// AMP is a record that encodes the fields necessary for atomic multi-path
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// payments.
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type AMP struct {
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rootShare [32]byte
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setID [32]byte
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childIndex uint32
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}
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// NewAMP generate a new AMP record with the given root_share, set_id, and
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// child_index.
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func NewAMP(rootShare, setID [32]byte, childIndex uint32) *AMP {
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return &{
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rootShare: rootShare,
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setID: setID,
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childIndex: childIndex,
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}
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}
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// RootShare returns the root share contained in the AMP record.
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func (a *AMP) RootShare() [32]byte {
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return a.rootShare
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}
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// SetID returns the set id contained in the AMP record.
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func (a *AMP) SetID() [32]byte {
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return a.setID
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}
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// ChildIndex returns the child index contained in the AMP record.
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func (a *AMP) ChildIndex() uint32 {
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return a.childIndex
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}
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// AMPEncoder writes the AMP record to the provided io.Writer.
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func AMPEncoder(w io.Writer, val interface{}, buf *[8]byte) error {
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if v, ok := val.(*AMP); ok {
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if err := tlv.EBytes32(w, &v.rootShare, buf); err != nil {
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return err
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}
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if err := tlv.EBytes32(w, &v.setID, buf); err != nil {
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return err
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}
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return tlv.ETUint32T(w, v.childIndex, buf)
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}
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return tlv.NewTypeForEncodingErr(val, "AMP")
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}
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const (
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// minAMPLength is the minimum length of a serialized AMP TLV record,
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// which occurs when the truncated encoding of child_index takes 0
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// bytes, leaving only the root_share and set_id.
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minAMPLength = 64
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// maxAMPLength is the maximum legnth of a serialized AMP TLV record,
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// which occurs when the truncated endoing of a child_index takes 2
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// bytes.
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maxAMPLength = 68
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)
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// AMPDecoder reads the AMP record from the provided io.Reader.
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func AMPDecoder(r io.Reader, val interface{}, buf *[8]byte, l uint64) error {
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if v, ok := val.(*AMP); ok && minAMPLength <= l && l <= maxAMPLength {
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if err := tlv.DBytes32(r, &v.rootShare, buf, 32); err != nil {
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return err
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}
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if err := tlv.DBytes32(r, &v.setID, buf, 32); err != nil {
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return err
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}
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return tlv.DTUint32(r, &v.childIndex, buf, l-minAMPLength)
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}
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return tlv.NewTypeForDecodingErr(val, "AMP", l, maxAMPLength)
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}
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// Record returns a tlv.Record that can be used to encode or decode this record.
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func (a *AMP) Record() tlv.Record {
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return tlv.MakeDynamicRecord(
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AMPOnionType, a, a.PayloadSize, AMPEncoder, AMPDecoder,
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)
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}
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// PayloadSize returns the size this record takes up in encoded form.
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func (a *AMP) PayloadSize() uint64 {
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return 32 + 32 + tlv.SizeTUint32(a.childIndex)
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}
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// String returns a human-readble description of the amp payload fields.
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func (a *AMP) String() string {
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return fmt.Sprintf("root_share=%x set_id=%x child_index=%d",
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a.rootShare, a.setID, a.childIndex)
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}
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