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export_tx.go
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/
export_tx.go
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// Copyright (C) 2019-2021, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package platformvm
import (
"errors"
"fmt"
"github.com/ava-labs/avalanchego/chains/atomic"
"github.com/ava-labs/avalanchego/database"
"github.com/ava-labs/avalanchego/ids"
"github.com/ava-labs/avalanchego/snow"
"github.com/ava-labs/avalanchego/utils/crypto"
"github.com/ava-labs/avalanchego/utils/math"
"github.com/ava-labs/avalanchego/vms/components/avax"
"github.com/ava-labs/avalanchego/vms/components/verify"
"github.com/ava-labs/avalanchego/vms/platformvm/stakeable"
"github.com/ava-labs/avalanchego/vms/secp256k1fx"
)
var (
errNoExportOutputs = errors.New("no export outputs")
errOutputsNotSorted = errors.New("outputs not sorted")
errOverflowExport = errors.New("overflow when computing export amount + txFee")
_ UnsignedAtomicTx = &UnsignedExportTx{}
)
// UnsignedExportTx is an unsigned ExportTx
type UnsignedExportTx struct {
BaseTx `serialize:"true"`
// Which chain to send the funds to
DestinationChain ids.ID `serialize:"true" json:"destinationChain"`
// Outputs that are exported to the chain
ExportedOutputs []*avax.TransferableOutput `serialize:"true" json:"exportedOutputs"`
}
// InitCtx sets the FxID fields in the inputs and outputs of this
// [UnsignedExportTx]. Also sets the [ctx] to the given [vm.ctx] so that
// the addresses can be json marshalled into human readable format
func (tx *UnsignedExportTx) InitCtx(ctx *snow.Context) {
tx.BaseTx.InitCtx(ctx)
for _, out := range tx.ExportedOutputs {
out.FxID = secp256k1fx.ID
out.InitCtx(ctx)
}
}
// InputUTXOs returns an empty set
func (tx *UnsignedExportTx) InputUTXOs() ids.Set { return nil }
// SyntacticVerify this transaction is well-formed
func (tx *UnsignedExportTx) SyntacticVerify(ctx *snow.Context) error {
switch {
case tx == nil:
return errNilTx
case tx.syntacticallyVerified: // already passed syntactic verification
return nil
case len(tx.ExportedOutputs) == 0:
return errNoExportOutputs
}
if err := tx.BaseTx.SyntacticVerify(ctx); err != nil {
return err
}
for _, out := range tx.ExportedOutputs {
if err := out.Verify(); err != nil {
return fmt.Errorf("output failed verification: %w", err)
}
if _, ok := out.Output().(*stakeable.LockOut); ok {
return errWrongLocktime
}
}
if !avax.IsSortedTransferableOutputs(tx.ExportedOutputs, Codec) {
return errOutputsNotSorted
}
tx.syntacticallyVerified = true
return nil
}
// Attempts to verify this transaction with the provided state.
func (tx *UnsignedExportTx) SemanticVerify(vm *VM, parentState MutableState, stx *Tx) error {
_, err := tx.AtomicExecute(vm, parentState, stx)
return err
}
// Execute this transaction.
func (tx *UnsignedExportTx) Execute(
vm *VM,
vs VersionedState,
stx *Tx,
) (func() error, error) {
if err := tx.SyntacticVerify(vm.ctx); err != nil {
return nil, err
}
outs := make([]*avax.TransferableOutput, len(tx.Outs)+len(tx.ExportedOutputs))
copy(outs, tx.Outs)
copy(outs[len(tx.Outs):], tx.ExportedOutputs)
if vm.bootstrapped.GetValue() {
if err := verify.SameSubnet(vm.ctx, tx.DestinationChain); err != nil {
return nil, err
}
}
// Verify the flowcheck
if err := vm.semanticVerifySpend(vs, tx, tx.Ins, outs, stx.Creds, vm.TxFee, vm.ctx.AVAXAssetID); err != nil {
return nil, fmt.Errorf("failed semanticVerifySpend: %w", err)
}
// Consume the UTXOS
consumeInputs(vs, tx.Ins)
// Produce the UTXOS
txID := tx.ID()
produceOutputs(vs, txID, vm.ctx.AVAXAssetID, tx.Outs)
return nil, nil
}
// AtomicOperations returns the shared memory requests
func (tx *UnsignedExportTx) AtomicOperations() (ids.ID, *atomic.Requests, error) {
txID := tx.ID()
elems := make([]*atomic.Element, len(tx.ExportedOutputs))
for i, out := range tx.ExportedOutputs {
utxo := &avax.UTXO{
UTXOID: avax.UTXOID{
TxID: txID,
OutputIndex: uint32(len(tx.Outs) + i),
},
Asset: avax.Asset{ID: out.AssetID()},
Out: out.Out,
}
utxoBytes, err := Codec.Marshal(CodecVersion, utxo)
if err != nil {
return ids.ID{}, nil, fmt.Errorf("failed to marshal UTXO: %w", err)
}
utxoID := utxo.InputID()
elem := &atomic.Element{
Key: utxoID[:],
Value: utxoBytes,
}
if out, ok := utxo.Out.(avax.Addressable); ok {
elem.Traits = out.Addresses()
}
elems[i] = elem
}
return tx.DestinationChain, &atomic.Requests{PutRequests: elems}, nil
}
// Execute this transaction and return the versioned state.
func (tx *UnsignedExportTx) AtomicExecute(
vm *VM,
parentState MutableState,
stx *Tx,
) (VersionedState, error) {
// Set up the state if this tx is committed
newState := newVersionedState(
parentState,
parentState.CurrentStakerChainState(),
parentState.PendingStakerChainState(),
)
_, err := tx.Execute(vm, newState, stx)
return newState, err
}
// Accept this transaction.
func (tx *UnsignedExportTx) AtomicAccept(ctx *snow.Context, batch database.Batch) error {
chainID, requests, err := tx.AtomicOperations()
if err != nil {
return err
}
return ctx.SharedMemory.Apply(map[ids.ID]*atomic.Requests{chainID: requests}, batch)
}
// Create a new transaction
func (vm *VM) newExportTx(
amount uint64, // Amount of tokens to export
chainID ids.ID, // Chain to send the UTXOs to
to ids.ShortID, // Address of chain recipient
keys []*crypto.PrivateKeySECP256K1R, // Pay the fee and provide the tokens
changeAddr ids.ShortID, // Address to send change to, if there is any
) (*Tx, error) {
toBurn, err := math.Add64(amount, vm.TxFee)
if err != nil {
return nil, errOverflowExport
}
ins, outs, _, signers, err := vm.stake(keys, 0, toBurn, changeAddr)
if err != nil {
return nil, fmt.Errorf("couldn't generate tx inputs/outputs: %w", err)
}
// Create the transaction
utx := &UnsignedExportTx{
BaseTx: BaseTx{BaseTx: avax.BaseTx{
NetworkID: vm.ctx.NetworkID,
BlockchainID: vm.ctx.ChainID,
Ins: ins,
Outs: outs, // Non-exported outputs
}},
DestinationChain: chainID,
ExportedOutputs: []*avax.TransferableOutput{{ // Exported to X-Chain
Asset: avax.Asset{ID: vm.ctx.AVAXAssetID},
Out: &secp256k1fx.TransferOutput{
Amt: amount,
OutputOwners: secp256k1fx.OutputOwners{
Locktime: 0,
Threshold: 1,
Addrs: []ids.ShortID{to},
},
},
}},
}
tx := &Tx{UnsignedTx: utx}
if err := tx.Sign(Codec, signers); err != nil {
return nil, err
}
return tx, utx.SyntacticVerify(vm.ctx)
}