9915780197

Committed 13 Jul 2024 12:30AM UTC coverage: 49.268% (-9.1%) from 58.413%

Build # 9915780197

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Merge pull request #8653 from ProofOfKeags/fn-prim

DynComms [0/n]: `fn` package additions

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76.09

/lnwire/features.go

package lnwire

import (
        "encoding/binary"
        "errors"
        "fmt"
        "io"

        "github.com/lightningnetwork/lnd/tlv"
)

var (
        // ErrFeaturePairExists signals an error in feature vector construction
        // where the opposing bit in a feature pair has already been set.
        ErrFeaturePairExists = errors.New("feature pair exists")

        // ErrFeatureStandard is returned when attempts to modify LND's known
        // set of features are made.
        ErrFeatureStandard = errors.New("feature is used in standard " +
                "protocol set")

        // ErrFeatureBitMaximum is returned when a feature bit exceeds the
        // maximum allowable value.
        ErrFeatureBitMaximum = errors.New("feature bit exceeds allowed maximum")
)

// FeatureBit represents a feature that can be enabled in either a local or
// global feature vector at a specific bit position. Feature bits follow the
// "it's OK to be odd" rule, where features at even bit positions must be known
// to a node receiving them from a peer while odd bits do not. In accordance,
// feature bits are usually assigned in pairs, first being assigned an odd bit
// position which may later be changed to the preceding even position once
// knowledge of the feature becomes required on the network.
type FeatureBit uint16

const (
        // DataLossProtectRequired is a feature bit that indicates that a peer
        // *requires* the other party know about the data-loss-protect optional
        // feature. If the remote peer does not know of such a feature, then
        // the sending peer SHOULD disconnect them. The data-loss-protect
        // feature allows a peer that's lost partial data to recover their
        // settled funds of the latest commitment state.
        DataLossProtectRequired FeatureBit = 0

        // DataLossProtectOptional is an optional feature bit that indicates
        // that the sending peer knows of this new feature and can activate it
        // it. The data-loss-protect feature allows a peer that's lost partial
        // data to recover their settled funds of the latest commitment state.
        DataLossProtectOptional FeatureBit = 1

        // InitialRoutingSync is a local feature bit meaning that the receiving
        // node should send a complete dump of routing information when a new
        // connection is established.
        InitialRoutingSync FeatureBit = 3

        // UpfrontShutdownScriptRequired is a feature bit which indicates that a
        // peer *requires* that the remote peer accept an upfront shutdown script to
        // which payout is enforced on cooperative closes.
        UpfrontShutdownScriptRequired FeatureBit = 4

        // UpfrontShutdownScriptOptional is an optional feature bit which indicates
        // that the peer will accept an upfront shutdown script to which payout is
        // enforced on cooperative closes.
        UpfrontShutdownScriptOptional FeatureBit = 5

        // GossipQueriesRequired is a feature bit that indicates that the
        // receiving peer MUST know of the set of features that allows nodes to
        // more efficiently query the network view of peers on the network for
        // reconciliation purposes.
        GossipQueriesRequired FeatureBit = 6

        // GossipQueriesOptional is an optional feature bit that signals that
        // the setting peer knows of the set of features that allows more
        // efficient network view reconciliation.
        GossipQueriesOptional FeatureBit = 7

        // TLVOnionPayloadRequired is a feature bit that indicates a node is
        // able to decode the new TLV information included in the onion packet.
        TLVOnionPayloadRequired FeatureBit = 8

        // TLVOnionPayloadOptional is an optional feature bit that indicates a
        // node is able to decode the new TLV information included in the onion
        // packet.
        TLVOnionPayloadOptional FeatureBit = 9

        // StaticRemoteKeyRequired is a required feature bit that signals that
        // within one's commitment transaction, the key used for the remote
        // party's non-delay output should not be tweaked.
        StaticRemoteKeyRequired FeatureBit = 12

        // StaticRemoteKeyOptional is an optional feature bit that signals that
        // within one's commitment transaction, the key used for the remote
        // party's non-delay output should not be tweaked.
        StaticRemoteKeyOptional FeatureBit = 13

        // PaymentAddrRequired is a required feature bit that signals that a
        // node requires payment addresses, which are used to mitigate probing
        // attacks on the receiver of a payment.
        PaymentAddrRequired FeatureBit = 14

        // PaymentAddrOptional is an optional feature bit that signals that a
        // node supports payment addresses, which are used to mitigate probing
        // attacks on the receiver of a payment.
        PaymentAddrOptional FeatureBit = 15

        // MPPRequired is a required feature bit that signals that the receiver
        // of a payment requires settlement of an invoice with more than one
        // HTLC.
        MPPRequired FeatureBit = 16

        // MPPOptional is an optional feature bit that signals that the receiver
        // of a payment supports settlement of an invoice with more than one
        // HTLC.
        MPPOptional FeatureBit = 17

        // WumboChannelsRequired is a required feature bit that signals that a
        // node is willing to accept channels larger than 2^24 satoshis.
        WumboChannelsRequired FeatureBit = 18

        // WumboChannelsOptional is an optional feature bit that signals that a
        // node is willing to accept channels larger than 2^24 satoshis.
        WumboChannelsOptional FeatureBit = 19

        // AnchorsRequired is a required feature bit that signals that the node
        // requires channels to be made using commitments having anchor
        // outputs.
        AnchorsRequired FeatureBit = 20

        // AnchorsOptional is an optional feature bit that signals that the
        // node supports channels to be made using commitments having anchor
        // outputs.
        AnchorsOptional FeatureBit = 21

        // AnchorsZeroFeeHtlcTxRequired is a required feature bit that signals
        // that the node requires channels having zero-fee second-level HTLC
        // transactions, which also imply anchor commitments.
        AnchorsZeroFeeHtlcTxRequired FeatureBit = 22

        // AnchorsZeroFeeHtlcTxOptional is an optional feature bit that signals
        // that the node supports channels having zero-fee second-level HTLC
        // transactions, which also imply anchor commitments.
        AnchorsZeroFeeHtlcTxOptional FeatureBit = 23

        // RouteBlindingRequired is a required feature bit that signals that
        // the node supports blinded payments.
        RouteBlindingRequired FeatureBit = 24

        // RouteBlindingOptional is an optional feature bit that signals that
        // the node supports blinded payments.
        RouteBlindingOptional FeatureBit = 25

        // ShutdownAnySegwitRequired is an required feature bit that signals
        // that the sender is able to properly handle/parse segwit witness
        // programs up to version 16. This enables utilization of Taproot
        // addresses for cooperative closure addresses.
        ShutdownAnySegwitRequired FeatureBit = 26

        // ShutdownAnySegwitOptional is an optional feature bit that signals
        // that the sender is able to properly handle/parse segwit witness
        // programs up to version 16. This enables utilization of Taproot
        // addresses for cooperative closure addresses.
        ShutdownAnySegwitOptional FeatureBit = 27

        // AMPRequired is a required feature bit that signals that the receiver
        // of a payment supports accepts spontaneous payments, i.e.
        // sender-generated preimages according to BOLT XX.
        AMPRequired FeatureBit = 30

        // AMPOptional is an optional feature bit that signals that the receiver
        // of a payment supports accepts spontaneous payments, i.e.
        // sender-generated preimages according to BOLT XX.
        AMPOptional FeatureBit = 31

        // ExplicitChannelTypeRequired is a required bit that denotes that a
        // connection established with this node is to use explicit channel
        // commitment types for negotiation instead of the existing implicit
        // negotiation methods. With this bit, there is no longer a "default"
        // implicit channel commitment type, allowing a connection to
        // open/maintain types of several channels over its lifetime.
        ExplicitChannelTypeRequired = 44

        // ExplicitChannelTypeOptional is an optional bit that denotes that a
        // connection established with this node is to use explicit channel
        // commitment types for negotiation instead of the existing implicit
        // negotiation methods. With this bit, there is no longer a "default"
        // implicit channel commitment type, allowing a connection to
        // TODO: Decide on actual feature bit value.
        ExplicitChannelTypeOptional = 45

        // ScidAliasRequired is a required feature bit that signals that the
        // node requires understanding of ShortChannelID aliases in the TLV
        // segment of the channel_ready message.
        ScidAliasRequired FeatureBit = 46

        // ScidAliasOptional is an optional feature bit that signals that the
        // node understands ShortChannelID aliases in the TLV segment of the
        // channel_ready message.
        ScidAliasOptional FeatureBit = 47

        // PaymentMetadataRequired is a required bit that denotes that if an
        // invoice contains metadata, it must be passed along with the payment
        // htlc(s).
        PaymentMetadataRequired = 48

        // PaymentMetadataOptional is an optional bit that denotes that if an
        // invoice contains metadata, it may be passed along with the payment
        // htlc(s).
        PaymentMetadataOptional = 49

        // ZeroConfRequired is a required feature bit that signals that the
        // node requires understanding of the zero-conf channel_type.
        ZeroConfRequired FeatureBit = 50

        // ZeroConfOptional is an optional feature bit that signals that the
        // node understands the zero-conf channel type.
        ZeroConfOptional FeatureBit = 51

        // KeysendRequired is a required bit that indicates that the node is
        // able and willing to accept keysend payments.
        KeysendRequired = 54

        // KeysendOptional is an optional bit that indicates that the node is
        // able and willing to accept keysend payments.
        KeysendOptional = 55

        // ScriptEnforcedLeaseOptional is an optional feature bit that signals
        // that the node requires channels having zero-fee second-level HTLC
        // transactions, which also imply anchor commitments, along with an
        // additional CLTV constraint of a channel lease's expiration height
        // applied to all outputs that pay directly to the channel initiator.
        //
        // TODO: Decide on actual feature bit value.
        ScriptEnforcedLeaseRequired FeatureBit = 2022

        // ScriptEnforcedLeaseOptional is an optional feature bit that signals
        // that the node requires channels having zero-fee second-level HTLC
        // transactions, which also imply anchor commitments, along with an
        // additional CLTV constraint of a channel lease's expiration height
        // applied to all outputs that pay directly to the channel initiator.
        //
        // TODO: Decide on actual feature bit value.
        ScriptEnforcedLeaseOptional FeatureBit = 2023

        // SimpleTaprootChannelsRequredFinal is a required bit that indicates
        // the node is able to create taproot-native channels. This is the
        // final feature bit to be used once the channel type is finalized.
        SimpleTaprootChannelsRequiredFinal = 80

        // SimpleTaprootChannelsOptionalFinal is an optional bit that indicates
        // the node is able to create taproot-native channels. This is the
        // final
        // feature bit to be used once the channel type is finalized.
        SimpleTaprootChannelsOptionalFinal = 81

        // SimpleTaprootChannelsRequredStaging is a required bit that indicates
        // the node is able to create taproot-native channels. This is a
        // feature bit used in the wild while the channel type is still being
        // finalized.
        SimpleTaprootChannelsRequiredStaging = 180

        // SimpleTaprootChannelsOptionalStaging is an optional bit that
        // indicates the node is able to create taproot-native channels. This
        // is a feature
        // bit used in the wild while the channel type is still being
        // finalized.
        SimpleTaprootChannelsOptionalStaging = 181

        // MaxBolt11Feature is the maximum feature bit value allowed in bolt 11
        // invoices.
        //
        // The base 32 encoded tagged fields in invoices are limited to 10 bits
        // to express the length of the field's data.
        //nolint:lll
        // See: https://github.com/lightning/bolts/blob/master/11-payment-encoding.md#tagged-fields
        //
        // With a maximum length field of 1023 (2^10 -1) and 5 bit encoding,
        // the highest feature bit that can be expressed is:
        // 1023 * 5 - 1 = 5114.
        MaxBolt11Feature = 5114
)

// IsRequired returns true if the feature bit is even, and false otherwise.
func (b FeatureBit) IsRequired() bool {
        return b&0x01 == 0x00
}

// Features is a mapping of known feature bits to a descriptive name. All known
// feature bits must be assigned a name in this mapping, and feature bit pairs
// must be assigned together for correct behavior.
var Features = map[FeatureBit]string{
        DataLossProtectRequired:              "data-loss-protect",
        DataLossProtectOptional:              "data-loss-protect",
        InitialRoutingSync:                   "initial-routing-sync",
        UpfrontShutdownScriptRequired:        "upfront-shutdown-script",
        UpfrontShutdownScriptOptional:        "upfront-shutdown-script",
        GossipQueriesRequired:                "gossip-queries",
        GossipQueriesOptional:                "gossip-queries",
        TLVOnionPayloadRequired:              "tlv-onion",
        TLVOnionPayloadOptional:              "tlv-onion",
        StaticRemoteKeyOptional:              "static-remote-key",
        StaticRemoteKeyRequired:              "static-remote-key",
        PaymentAddrOptional:                  "payment-addr",
        PaymentAddrRequired:                  "payment-addr",
        MPPOptional:                          "multi-path-payments",
        MPPRequired:                          "multi-path-payments",
        AnchorsRequired:                      "anchor-commitments",
        AnchorsOptional:                      "anchor-commitments",
        AnchorsZeroFeeHtlcTxRequired:         "anchors-zero-fee-htlc-tx",
        AnchorsZeroFeeHtlcTxOptional:         "anchors-zero-fee-htlc-tx",
        WumboChannelsRequired:                "wumbo-channels",
        WumboChannelsOptional:                "wumbo-channels",
        AMPRequired:                          "amp",
        AMPOptional:                          "amp",
        PaymentMetadataOptional:              "payment-metadata",
        PaymentMetadataRequired:              "payment-metadata",
        ExplicitChannelTypeOptional:          "explicit-commitment-type",
        ExplicitChannelTypeRequired:          "explicit-commitment-type",
        KeysendOptional:                      "keysend",
        KeysendRequired:                      "keysend",
        ScriptEnforcedLeaseRequired:          "script-enforced-lease",
        ScriptEnforcedLeaseOptional:          "script-enforced-lease",
        ScidAliasRequired:                    "scid-alias",
        ScidAliasOptional:                    "scid-alias",
        ZeroConfRequired:                     "zero-conf",
        ZeroConfOptional:                     "zero-conf",
        RouteBlindingRequired:                "route-blinding",
        RouteBlindingOptional:                "route-blinding",
        ShutdownAnySegwitRequired:            "shutdown-any-segwit",
        ShutdownAnySegwitOptional:            "shutdown-any-segwit",
        SimpleTaprootChannelsRequiredFinal:   "simple-taproot-chans",
        SimpleTaprootChannelsOptionalFinal:   "simple-taproot-chans",
        SimpleTaprootChannelsRequiredStaging: "simple-taproot-chans-x",
        SimpleTaprootChannelsOptionalStaging: "simple-taproot-chans-x",
}

// RawFeatureVector represents a set of feature bits as defined in BOLT-09.  A
// RawFeatureVector itself just stores a set of bit flags but can be used to
// construct a FeatureVector which binds meaning to each bit. Feature vectors
// can be serialized and deserialized to/from a byte representation that is
// transmitted in Lightning network messages.
type RawFeatureVector struct {
        features map[FeatureBit]struct{}
}

// NewRawFeatureVector creates a feature vector with all of the feature bits
// given as arguments enabled.
func NewRawFeatureVector(bits ...FeatureBit) *RawFeatureVector {
        fv := &RawFeatureVector{features: make(map[FeatureBit]struct{})}
        for _, bit := range bits {
                fv.Set(bit)
        }
        return fv
}

// IsEmpty returns whether the feature vector contains any feature bits.
func (fv RawFeatureVector) IsEmpty() bool {
        return len(fv.features) == 0
}

// OnlyContains determines whether only the specified feature bits are found.
func (fv RawFeatureVector) OnlyContains(bits ...FeatureBit) bool {
        if len(bits) != len(fv.features) {
                return false
        }
        for _, bit := range bits {
                if !fv.IsSet(bit) {
                        return false
                }
        }
        return true
}

// Equals determines whether two features vectors contain exactly the same
// features.
func (fv RawFeatureVector) Equals(other *RawFeatureVector) bool {
        if len(fv.features) != len(other.features) {
                return false
        }
        for bit := range fv.features {
                if _, ok := other.features[bit]; !ok {
                        return false
                }
        }
        return true
}

// Merges sets all feature bits in other on the receiver's feature vector.
func (fv *RawFeatureVector) Merge(other *RawFeatureVector) error {
        for bit := range other.features {
                err := fv.SafeSet(bit)
                if err != nil {
                        return err
                }
        }
        return nil
}

// ValidateUpdate checks whether a feature vector can safely be updated to the
// new feature vector provided, checking that it does not alter any of the
// "standard" features that are defined by LND. The new feature vector should
// be inclusive of all features in the original vector that it still wants to
// advertise, setting and unsetting updates as desired. Features in the vector
// are also checked against a maximum inclusive value, as feature vectors in
// different contexts have different maximum values.
func (fv *RawFeatureVector) ValidateUpdate(other *RawFeatureVector,
        maximumValue FeatureBit) error {

        // Run through the new set of features and check that we're not adding
        // any feature bits that are defined but not set in LND.
        for feature := range other.features {
                if fv.IsSet(feature) {
                        continue
                }

                if feature > maximumValue {
                        return fmt.Errorf("can't set feature bit %d: %w %v",
                                feature, ErrFeatureBitMaximum,
                                maximumValue)
                }

                if name, known := Features[feature]; known {
                        return fmt.Errorf("can't set feature "+
                                "bit %d (%v): %w", feature, name,
                                ErrFeatureStandard)
                }
        }

        // Check that the new feature vector for this set does not unset any
        // features that are standard in LND by comparing the features in our
        // current set to the omitted values in the new set.
        for feature := range fv.features {
                if other.IsSet(feature) {
                        continue
                }

                if name, known := Features[feature]; known {
                        return fmt.Errorf("can't unset feature "+
                                "bit %d (%v): %w", feature, name,
                                ErrFeatureStandard)
                }
        }

        return nil
}

// ValidatePairs checks each feature bit in a raw vector to ensure that the
// opposing bit is not set, validating that the vector has either the optional
// or required bit set, not both.
func (fv *RawFeatureVector) ValidatePairs() error {
        for feature := range fv.features {
                if _, ok := fv.features[feature^1]; ok {
                        return ErrFeaturePairExists
                }
        }

        return nil
}

// Clone makes a copy of a feature vector.
func (fv *RawFeatureVector) Clone() *RawFeatureVector {
        newFeatures := NewRawFeatureVector()
        for bit := range fv.features {
                newFeatures.Set(bit)
        }
        return newFeatures
}

// IsSet returns whether a particular feature bit is enabled in the vector.
func (fv *RawFeatureVector) IsSet(feature FeatureBit) bool {
        _, ok := fv.features[feature]
        return ok
}

// Set marks a feature as enabled in the vector.
func (fv *RawFeatureVector) Set(feature FeatureBit) {
        fv.features[feature] = struct{}{}
}

// SafeSet sets the chosen feature bit in the feature vector, but returns an
// error if the opposing feature bit is already set. This ensures both that we
// are creating properly structured feature vectors, and in some cases, that
// peers are sending properly encoded ones, i.e. it can't be both optional and
// required.
func (fv *RawFeatureVector) SafeSet(feature FeatureBit) error {
        if _, ok := fv.features[feature^1]; ok {
                return ErrFeaturePairExists
        }

        fv.Set(feature)
        return nil
}

// Unset marks a feature as disabled in the vector.
func (fv *RawFeatureVector) Unset(feature FeatureBit) {
        delete(fv.features, feature)
}

// SerializeSize returns the number of bytes needed to represent feature vector
// in byte format.
func (fv *RawFeatureVector) SerializeSize() int {
        // We calculate byte-length via the largest bit index.
        return fv.serializeSize(8)
}

// SerializeSize32 returns the number of bytes needed to represent feature
// vector in base32 format.
func (fv *RawFeatureVector) SerializeSize32() int {
        // We calculate base32-length via the largest bit index.
        return fv.serializeSize(5)
}

// serializeSize returns the number of bytes required to encode the feature
// vector using at most width bits per encoded byte.
func (fv *RawFeatureVector) serializeSize(width int) int {
        // Find the largest feature bit index
        max := -1
        for feature := range fv.features {
                index := int(feature)
                if index > max {
                        max = index
                }
        }
        if max == -1 {
                return 0
        }

        return max/width + 1
}

// Encode writes the feature vector in byte representation. Every feature
// encoded as a bit, and the bit vector is serialized using the least number of
// bytes. Since the bit vector length is variable, the first two bytes of the
// serialization represent the length.
func (fv *RawFeatureVector) Encode(w io.Writer) error {
        // Write length of feature vector.
        var l [2]byte
        length := fv.SerializeSize()
        binary.BigEndian.PutUint16(l[:], uint16(length))
        if _, err := w.Write(l[:]); err != nil {
                return err
        }

        return fv.encode(w, length, 8)
}

// EncodeBase256 writes the feature vector in base256 representation. Every
// feature is encoded as a bit, and the bit vector is serialized using the least
// number of bytes.
func (fv *RawFeatureVector) EncodeBase256(w io.Writer) error {
        length := fv.SerializeSize()
        return fv.encode(w, length, 8)
}

// EncodeBase32 writes the feature vector in base32 representation. Every feature
// is encoded as a bit, and the bit vector is serialized using the least number of
// bytes.
func (fv *RawFeatureVector) EncodeBase32(w io.Writer) error {
        length := fv.SerializeSize32()
        return fv.encode(w, length, 5)
}

// encode writes the feature vector
func (fv *RawFeatureVector) encode(w io.Writer, length, width int) error {
        // Generate the data and write it.
        data := make([]byte, length)
        for feature := range fv.features {
                byteIndex := int(feature) / width
                bitIndex := int(feature) % width
                data[length-byteIndex-1] |= 1 << uint(bitIndex)
        }

        _, err := w.Write(data)
        return err
}

// Decode reads the feature vector from its byte representation. Every feature
// is encoded as a bit, and the bit vector is serialized using the least number
// of bytes. Since the bit vector length is variable, the first two bytes of the
// serialization represent the length.
func (fv *RawFeatureVector) Decode(r io.Reader) error {
        // Read the length of the feature vector.
        var l [2]byte
        if _, err := io.ReadFull(r, l[:]); err != nil {
                return err
        }
        length := binary.BigEndian.Uint16(l[:])

        return fv.decode(r, int(length), 8)
}

// DecodeBase256 reads the feature vector from its base256 representation. Every
// feature encoded as a bit, and the bit vector is serialized using the least
// number of bytes.
func (fv *RawFeatureVector) DecodeBase256(r io.Reader, length int) error {
        return fv.decode(r, length, 8)
}

// DecodeBase32 reads the feature vector from its base32 representation. Every
// feature encoded as a bit, and the bit vector is serialized using the least
// number of bytes.
func (fv *RawFeatureVector) DecodeBase32(r io.Reader, length int) error {
        return fv.decode(r, length, 5)
}

// decode reads a feature vector from the next length bytes of the io.Reader,
// assuming each byte has width feature bits encoded per byte.
func (fv *RawFeatureVector) decode(r io.Reader, length, width int) error {
        // Read the feature vector data.
        data := make([]byte, length)
        if _, err := io.ReadFull(r, data); err != nil {
                return err
        }

        // Set feature bits from parsed data.
        bitsNumber := len(data) * width
        for i := 0; i < bitsNumber; i++ {
                byteIndex := int(i / width)
                bitIndex := uint(i % width)
                if (data[length-byteIndex-1]>>bitIndex)&1 == 1 {
                        fv.Set(FeatureBit(i))
                }
        }

        return nil
}

// sizeFunc returns the length required to encode the feature vector.
func (fv *RawFeatureVector) sizeFunc() uint64 {
        return uint64(fv.SerializeSize())
}

// Record returns a TLV record that can be used to encode/decode raw feature
// vectors. Note that the length of the feature vector is not included, because
// it is covered by the TLV record's length field.
func (fv *RawFeatureVector) Record(recordType tlv.Type) tlv.Record {
        return tlv.MakeDynamicRecord(
                recordType, fv, fv.sizeFunc, rawFeatureEncoder,
                rawFeatureDecoder,
        )
}

// rawFeatureEncoder is a custom TLV encoder for raw feature vectors.
func rawFeatureEncoder(w io.Writer, val interface{}, _ *[8]byte) error {
        if f, ok := val.(*RawFeatureVector); ok {
                return f.encode(w, f.SerializeSize(), 8)
        }

        return tlv.NewTypeForEncodingErr(val, "*lnwire.RawFeatureVector")
}

// rawFeatureDecoder is a custom TLV decoder for raw feature vectors.
func rawFeatureDecoder(r io.Reader, val interface{}, _ *[8]byte,
        l uint64) error {

        if f, ok := val.(*RawFeatureVector); ok {
                return f.decode(r, int(l), 8)
        }

        return tlv.NewTypeForEncodingErr(val, "*lnwire.RawFeatureVector")
}

// FeatureVector represents a set of enabled features. The set stores
// information on enabled flags and metadata about the feature names. A feature
// vector is serializable to a compact byte representation that is included in
// Lightning network messages.
type FeatureVector struct {
        *RawFeatureVector
        featureNames map[FeatureBit]string
}

// NewFeatureVector constructs a new FeatureVector from a raw feature vector
// and mapping of feature definitions. If the feature vector argument is nil, a
// new one will be constructed with no enabled features.
func NewFeatureVector(featureVector *RawFeatureVector,
        featureNames map[FeatureBit]string) *FeatureVector {

        if featureVector == nil {
                featureVector = NewRawFeatureVector()
        }
        return &FeatureVector{
                RawFeatureVector: featureVector,
                featureNames:     featureNames,
        }
}

// EmptyFeatureVector returns a feature vector with no bits set.
func EmptyFeatureVector() *FeatureVector {
        return NewFeatureVector(nil, Features)
}

// Record implements the RecordProducer interface for FeatureVector. Note that
// it uses a zero-value type is used to produce the record, as we expect this
// type value to be overwritten when used in generic TLV record production.
// This allows a single Record function to serve in the many different contexts
// in which feature vectors are encoded. This record wraps the encoding/
// decoding for our raw feature vectors so that we can directly parse fully
// formed feature vector types.
func (fv *FeatureVector) Record() tlv.Record {
        return tlv.MakeDynamicRecord(0, fv, fv.sizeFunc,
                func(w io.Writer, val interface{}, buf *[8]byte) error {
                        if f, ok := val.(*FeatureVector); ok {
                                return rawFeatureEncoder(
                                        w, f.RawFeatureVector, buf,
                                )
                        }

                        return tlv.NewTypeForEncodingErr(
                                val, "*lnwire.FeatureVector",
                        )
                },
                func(r io.Reader, val interface{}, buf *[8]byte,
                        l uint64) error {

                        if f, ok := val.(*FeatureVector); ok {
                                features := NewFeatureVector(nil, Features)
                                err := rawFeatureDecoder(
                                        r, features.RawFeatureVector, buf, l,
                                )
                                if err != nil {
                                        return err
                                }

                                *f = *features

                                return nil
                        }

                        return tlv.NewTypeForDecodingErr(
                                val, "*lnwire.FeatureVector", l, l,
                        )
                },
        )
}

// HasFeature returns whether a particular feature is included in the set. The
// feature can be seen as set either if the bit is set directly OR the queried
// bit has the same meaning as its corresponding even/odd bit, which is set
// instead. The second case is because feature bits are generally assigned in
// pairs where both the even and odd position represent the same feature.
func (fv *FeatureVector) HasFeature(feature FeatureBit) bool {
        return fv.IsSet(feature) ||
                (fv.isFeatureBitPair(feature) && fv.IsSet(feature^1))
}

// RequiresFeature returns true if the referenced feature vector *requires*
// that the given required bit be set. This method can be used with both
// optional and required feature bits as a parameter.
func (fv *FeatureVector) RequiresFeature(feature FeatureBit) bool {
        // If we weren't passed a required feature bit, then we'll flip the
        // lowest bit to query for the required version of the feature. This
        // lets callers pass in both the optional and required bits.
        if !feature.IsRequired() {
                feature ^= 1
        }

        return fv.IsSet(feature)
}

// UnknownRequiredFeatures returns a list of feature bits set in the vector
// that are unknown and in an even bit position. Feature bits with an even
// index must be known to a node receiving the feature vector in a message.
func (fv *FeatureVector) UnknownRequiredFeatures() []FeatureBit {
        var unknown []FeatureBit
        for feature := range fv.features {
                if feature%2 == 0 && !fv.IsKnown(feature) {
                        unknown = append(unknown, feature)
                }
        }
        return unknown
}

// UnknownFeatures returns a boolean if a feature vector contains *any*
// unknown features (even if they are odd).
func (fv *FeatureVector) UnknownFeatures() bool {
        for feature := range fv.features {
                if !fv.IsKnown(feature) {
                        return true
                }
        }

        return false
}

// Name returns a string identifier for the feature represented by this bit. If
// the bit does not represent a known feature, this returns a string indicating
// as such.
func (fv *FeatureVector) Name(bit FeatureBit) string {
        name, known := fv.featureNames[bit]
        if !known {
                return "unknown"
        }
        return name
}

// IsKnown returns whether this feature bit represents a known feature.
func (fv *FeatureVector) IsKnown(bit FeatureBit) bool {
        _, known := fv.featureNames[bit]
        return known
}

// isFeatureBitPair returns whether this feature bit and its corresponding
// even/odd bit both represent the same feature. This may often be the case as
// bits are generally assigned in pairs, first being assigned an odd bit
// position then being promoted to an even bit position once the network is
// ready.
func (fv *FeatureVector) isFeatureBitPair(bit FeatureBit) bool {
        name1, known1 := fv.featureNames[bit]
        name2, known2 := fv.featureNames[bit^1]
        return known1 && known2 && name1 == name2
}

// Features returns the set of raw features contained in the feature vector.
func (fv *FeatureVector) Features() map[FeatureBit]struct{} {
        fs := make(map[FeatureBit]struct{}, len(fv.RawFeatureVector.features))
        for b := range fv.RawFeatureVector.features {
                fs[b] = struct{}{}
        }
        return fs
}

// Clone copies a feature vector, carrying over its feature bits. The feature
// names are not copied.
func (fv *FeatureVector) Clone() *FeatureVector {
        features := fv.RawFeatureVector.Clone()
        return NewFeatureVector(features, fv.featureNames)
}

lightningnetwork / lnd / 9915780197

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