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ForwardingService: inline CoinSelector creation into forward()

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Sean Gilligan 2024-04-22 11:19:19 -07:00 • committed by Andreas Schildbach
parent 490b3fe956
commit ffcd879208
1 changed files with 7 additions and 16 deletions
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23
examples/src/main/java/org/bitcoinj/examples/ForwardingService.java
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@ -17,7 +17,6 @@
package org.bitcoinj.examples; package org.bitcoinj.examples;
import org.bitcoinj.base.BitcoinNetwork; import org.bitcoinj.base.BitcoinNetwork;
import org.bitcoinj.base.Sha256Hash;
import org.bitcoinj.base.Address; import org.bitcoinj.base.Address;
import org.bitcoinj.base.Coin; import org.bitcoinj.base.Coin;
import org.bitcoinj.base.AddressParser; import org.bitcoinj.base.AddressParser;
@ -160,16 +159,20 @@ public class ForwardingService implements Closeable {
} }
/** /**
* Forward an incoming transaction by creating a new transaction, signing, and sending to the specified address. * Forward an incoming transaction by creating a new transaction, signing, and sending to the specified address. The
* inputs for the new transaction should only come from the incoming transaction, so we use a custom {@link CoinSelector}
* that only selects wallet UTXOs with the correct parent transaction ID.
* @param wallet The active wallet * @param wallet The active wallet
* @param incomingTx the received transaction * @param incomingTx the received transaction
* @param forwardingAddress the address to send to * @param forwardingAddress the address to send to
* @return A future for a TransactionBroadcast object that completes when relay is acknowledged by peers * @return A future for a TransactionBroadcast object that completes when relay is acknowledged by peers
*/ */
private CompletableFuture<TransactionBroadcast> forward(Wallet wallet, Transaction incomingTx, Address forwardingAddress) { private CompletableFuture<TransactionBroadcast> forward(Wallet wallet, Transaction incomingTx, Address forwardingAddress) {
// Send coins received in incomingTx onwards by sending exactly the outputs that have been sent to us // Send coins received in incomingTx onwards by sending exactly the UTXOs we have just received.
// We're not truly emptying the wallet because we're limiting the available outputs with a CoinSelector.
SendRequest sendRequest = SendRequest.emptyWallet(forwardingAddress); SendRequest sendRequest = SendRequest.emptyWallet(forwardingAddress);
sendRequest.coinSelector = forwardingCoinSelector(incomingTx.getTxId()); // Use a CoinSelector that only returns wallet UTXOs from the incoming transaction.
sendRequest.coinSelector = CoinSelector.fromPredicate(output -> Objects.equals(output.getParentTransactionHash(), incomingTx.getTxId()));
System.out.printf("Creating outgoing transaction for %s...\n", forwardingAddress); System.out.printf("Creating outgoing transaction for %s...\n", forwardingAddress);
return wallet.sendTransaction(sendRequest) return wallet.sendTransaction(sendRequest)
.thenCompose(broadcast -> { .thenCompose(broadcast -> {
@ -181,16 +184,4 @@ public class ForwardingService implements Closeable {
static String getPrefix(BitcoinNetwork network) { static String getPrefix(BitcoinNetwork network) {
return String.format("forwarding-service-%s", network.toString()); return String.format("forwarding-service-%s", network.toString());
} }
/**
* Create a CoinSelector that only returns outputs from a given parent transaction.
* <p>
* This is using the idea of partial function application to create a 2-argument function for coin selection
* with a third, fixed argument of the transaction id.
* @param parentTxId The parent transaction hash
* @return a coin selector
*/
static CoinSelector forwardingCoinSelector(Sha256Hash parentTxId) {
return CoinSelector.fromPredicate(output -> Objects.equals(output.getParentTransactionHash(), parentTxId));
}
} }