Transaction, TransactionInput, TransactionOutPoint: add static constructors for the elements of a coinbase

This should reduce misuse of the standard constructors.

core/src/main/java/org/bitcoinj/core/Block.java

@@ -253,18 +253,12 @@ public class Block extends Message {
 
     public static Block createGenesis(NetworkParameters n) {
         Block genesisBlock = new Block(n, BLOCK_VERSION_GENESIS);
-        Transaction t = createGenesisTransaction(n, genesisTxInputScriptBytes, FIFTY_COINS, genesisTxScriptPubKeyBytes);
+        Transaction tx = Transaction.coinbase(n, genesisTxInputScriptBytes);
-        genesisBlock.addTransaction(t);
+        tx.addOutput(new TransactionOutput(tx, FIFTY_COINS, genesisTxScriptPubKeyBytes));
+        genesisBlock.addTransaction(tx);
         return genesisBlock;
     }
 
-    private static Transaction createGenesisTransaction(NetworkParameters n, byte[] inputScriptBytes, Coin amount, byte[] scriptPubKeyBytes) {
-        Transaction t = new Transaction(n);
-        t.addInput(new TransactionInput(t, inputScriptBytes));
-        t.addOutput(new TransactionOutput(t, amount, scriptPubKeyBytes));
-        return t;
-    }
-
     // A script containing the difficulty bits and the following message:
     //
     //   "The Times 03/Jan/2009 Chancellor on brink of second bailout for banks"
@@ -891,7 +885,7 @@ public class Block extends Message {
         //
         // Here we will do things a bit differently so a new address isn't needed every time. We'll put a simple
         // counter in the scriptSig so every transaction has a different hash.
-        coinbase.addInput(new TransactionInput(coinbase,
+        coinbase.addInput(TransactionInput.coinbaseInput(coinbase,
                 inputBuilder.build().getProgram()));
         coinbase.addOutput(new TransactionOutput(coinbase, value,
                 ScriptBuilder.createP2PKOutputScript(ECKey.fromPublicOnly(pubKeyTo)).getProgram()));

core/src/main/java/org/bitcoinj/core/Transaction.java

@@ -222,6 +222,31 @@ public class Transaction extends Message {
     @Nullable
     private String memo;
 
+    /**
+     * Constructs an incomplete coinbase transaction with a minimal input script and no outputs.
+     *
+     * @param params network to use
+     * @return coinbase transaction
+     */
+    public static Transaction coinbase(NetworkParameters params) {
+        Transaction tx = new Transaction(params);
+        tx.addInput(TransactionInput.coinbaseInput(tx, new byte[2])); // 2 is minimum
+        return tx;
+    }
+
+    /**
+     * Constructs an incomplete coinbase transaction with given bytes for the input script and no outputs.
+     *
+     * @param params            network to use
+     * @param inputScriptBytes  arbitrary bytes for the coinbase input
+     * @return coinbase transaction
+     */
+    public static Transaction coinbase(NetworkParameters params, byte[] inputScriptBytes) {
+        Transaction tx = new Transaction(params);
+        tx.addInput(TransactionInput.coinbaseInput(tx, inputScriptBytes));
+        return tx;
+    }
+
     public Transaction(NetworkParameters params) {
         super(params);
         version = 1;

core/src/main/java/org/bitcoinj/core/TransactionInput.java

@@ -92,9 +92,15 @@ public class TransactionInput extends Message {
 
     /**
      * Creates an input that connects to nothing - used only in creation of coinbase transactions.
+     *
+     * @param parentTransaction parent transaction
+     * @param scriptBytes       arbitrary bytes in the script
      */
-    public TransactionInput(@Nullable Transaction parentTransaction, byte[] scriptBytes) {
+    public static TransactionInput coinbaseInput(Transaction parentTransaction, byte[] scriptBytes) {
-        this(parentTransaction, scriptBytes, new TransactionOutPoint(UNCONNECTED, (Transaction) null));
+        Objects.requireNonNull(parentTransaction);
+        checkArgument(scriptBytes.length >= 2 && scriptBytes.length <= 100, () ->
+                "script must be between 2 and 100 bytes: " + scriptBytes.length);
+        return new TransactionInput(parentTransaction, scriptBytes, TransactionOutPoint.UNCONNECTED);
     }
 
     public TransactionInput(@Nullable Transaction parentTransaction, byte[] scriptBytes,

core/src/main/java/org/bitcoinj/core/TransactionOutPoint.java

@@ -47,6 +47,10 @@ public class TransactionOutPoint extends Message {
 
     static final int MESSAGE_LENGTH = 36;
 
+    /** Special outpoint that normally marks a coinbase input. It's also used as a test dummy. */
+    public static final TransactionOutPoint UNCONNECTED =
+            new TransactionOutPoint(ByteUtils.MAX_UNSIGNED_INTEGER, Sha256Hash.ZERO_HASH);
+
     /** Hash of the transaction to which we refer. */
     private Sha256Hash hash;
     /** Which output of that transaction we are talking about. */
@@ -58,18 +62,13 @@ public class TransactionOutPoint extends Message {
     // The connected output.
     TransactionOutput connectedOutput;
 
-    public TransactionOutPoint(long index, @Nullable Transaction fromTx) {
+    public TransactionOutPoint(long index, Transaction fromTx) {
         super();
         checkArgument(index >= 0 && index <= ByteUtils.MAX_UNSIGNED_INTEGER, () ->
                 "index out of range: " + index);
         this.index = index;
-        if (fromTx != null) {
+        this.hash = fromTx.getTxId();
-            this.hash = fromTx.getTxId();
+        this.fromTx = fromTx;
-            this.fromTx = fromTx;
-        } else {
-            // This happens when constructing the genesis block.
-            hash = Sha256Hash.ZERO_HASH;
-        }
     }
 
     public TransactionOutPoint(long index, Sha256Hash hash) {

core/src/main/java/org/bitcoinj/testing/FakeTxBuilder.java

@@ -74,14 +74,10 @@ public class FakeTxBuilder {
 
     /** Create a fake coinbase transaction. */
     public static Transaction createFakeCoinbaseTx(final NetworkParameters params) {
-        TransactionOutPoint outpoint = new TransactionOutPoint(ByteUtils.MAX_UNSIGNED_INTEGER, Sha256Hash.ZERO_HASH);
+        Transaction tx = Transaction.coinbase(params);
-        TransactionInput input = new TransactionInput(null, new byte[0], outpoint);
-        Transaction tx = new Transaction(params);
-        tx.addInput(input);
         TransactionOutput outputToMe = new TransactionOutput(tx, Coin.FIFTY_COINS, randomAddress(params));
-        tx.addOutput(outputToMe);
-
         checkState(tx.isCoinBase());
+        tx.addOutput(outputToMe);
         return tx;
     }
 

core/src/test/java/org/bitcoinj/core/FullBlockTestGenerator.java

@@ -1007,7 +1007,7 @@ public class FullBlockTestGenerator {
         NewBlock b51 = createNextBlock(b44, chainHeadHeight + 16, out15, null);
         {
             Transaction coinbase = new Transaction(params);
-            coinbase.addInput(new TransactionInput(coinbase, new byte[]{(byte) 0xff, 110, 1}));
+            coinbase.addInput(TransactionInput.coinbaseInput(coinbase, new byte[]{(byte) 0xff, 110, 1}));
             coinbase.addOutput(new TransactionOutput(coinbase, SATOSHI, outScriptBytes));
             b51.block.addTransaction(coinbase, false);
         }

core/src/test/java/org/bitcoinj/core/TransactionInputTest.java

@@ -36,6 +36,7 @@ import java.util.List;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertTrue;
 
 public class TransactionInputTest {
     private static final NetworkParameters TESTNET = TestNet3Params.get();
@@ -105,4 +106,10 @@ public class TransactionInputTest {
         assertNull(txInToDisconnect.getOutpoint().fromTx);
         assertNull(txInToDisconnect.getOutpoint().connectedOutput);
     }
+
+    @Test
+    public void coinbaseInput() {
+        TransactionInput coinbaseInput = TransactionInput.coinbaseInput(new Transaction(TESTNET), new byte[2]);
+        assertTrue(coinbaseInput.isCoinBase());
+    }
 }

core/src/test/java/org/bitcoinj/core/TransactionTest.java

@@ -489,7 +489,7 @@ public class TransactionTest {
     @Test
     public void testToStringWhenIteratingOverAnInputCatchesAnException() {
         Transaction tx = FakeTxBuilder.createFakeTx(TESTNET);
-        TransactionInput ti = new TransactionInput(tx, new byte[0]) {
+        TransactionInput ti = new TransactionInput(tx, new byte[0], TransactionOutPoint.UNCONNECTED) {
             @Override
             public Script getScriptSig() throws ScriptException {
                 throw new ScriptException(ScriptError.SCRIPT_ERR_UNKNOWN_ERROR, "");

core/src/test/java/org/bitcoinj/protocols/payments/PaymentSessionTest.java

@@ -25,6 +25,7 @@ import org.bitcoinj.base.Address;
 import org.bitcoinj.base.Coin;
 import org.bitcoinj.base.internal.TimeUtils;
 import org.bitcoinj.core.Context;
+import org.bitcoinj.core.TransactionOutPoint;
 import org.bitcoinj.crypto.ECKey;
 import org.bitcoinj.core.NetworkParameters;
 import org.bitcoinj.core.Transaction;
@@ -90,7 +91,7 @@ public class PaymentSessionTest {
 
         // Send the payment and verify that the correct information is sent.
         // Add a dummy input to tx so it is considered valid.
-        tx.addInput(new TransactionInput(tx, outputToMe.getScriptBytes()));
+        tx.addInput(new TransactionInput(tx, outputToMe.getScriptBytes(), TransactionOutPoint.UNCONNECTED));
         ArrayList<Transaction> txns = new ArrayList<>();
         txns.add(tx);
         Address refundAddr = serverKey.toAddress(ScriptType.P2PKH, BitcoinNetwork.TESTNET);
@@ -130,7 +131,7 @@ public class PaymentSessionTest {
         assertTrue(paymentSession.isExpired());
         // Send the payment and verify that an exception is thrown.
         // Add a dummy input to tx so it is considered valid.
-        tx.addInput(new TransactionInput(tx, outputToMe.getScriptBytes()));
+        tx.addInput(new TransactionInput(tx, outputToMe.getScriptBytes(), TransactionOutPoint.UNCONNECTED));
         ArrayList<Transaction> txns = new ArrayList<>();
         txns.add(tx);
 
@@ -169,7 +170,7 @@ public class PaymentSessionTest {
 
         // Send the payment and verify that the correct information is sent.
         // Add a dummy input to tx so it is considered valid.
-        tx.addInput(new TransactionInput(tx, outputToMe.getScriptBytes()));
+        tx.addInput(new TransactionInput(tx, outputToMe.getScriptBytes(), TransactionOutPoint.UNCONNECTED));
         ArrayList<Transaction> txns = new ArrayList<>();
         txns.add(tx);
         Address refundAddr = serverKey.toAddress(ScriptType.P2PKH, BitcoinNetwork.TESTNET);

core/src/test/java/org/bitcoinj/script/ScriptTest.java

@@ -248,7 +248,7 @@ public class ScriptTest {
     public void testOp0() {
         // Check that OP_0 doesn't NPE and pushes an empty stack frame.
         Transaction tx = new Transaction(TESTNET);
-        tx.addInput(new TransactionInput(tx, new byte[] {}));
+        tx.addInput(new TransactionInput(tx, new byte[0], TransactionOutPoint.UNCONNECTED));
         Script script = new ScriptBuilder().smallNum(0).build();
 
         LinkedList<byte[]> stack = new LinkedList<>();
@@ -354,7 +354,7 @@ public class ScriptTest {
         tx.setLockTime(0);
 
         TransactionInput txInput = new TransactionInput(null,
-                new ScriptBuilder().number(0).number(0).build().getProgram());
+                new ScriptBuilder().number(0).number(0).build().getProgram(), TransactionOutPoint.UNCONNECTED);
         txInput.setSequenceNumber(TransactionInput.NO_SEQUENCE);
         tx.addInput(txInput);
 
@@ -369,7 +369,8 @@ public class ScriptTest {
         tx.setVersion(1);
         tx.setLockTime(0);
 
-        TransactionInput txInput = new TransactionInput(creditingTransaction, scriptSig.getProgram());
+        TransactionInput txInput = new TransactionInput(creditingTransaction, scriptSig.getProgram(),
+                TransactionOutPoint.UNCONNECTED);
         txInput.setSequenceNumber(TransactionInput.NO_SEQUENCE);
         tx.addInput(txInput);
 

core/src/test/java/org/bitcoinj/wallet/DefaultRiskAnalysisTest.java

@@ -21,6 +21,7 @@ import org.bitcoinj.base.Coin;
 import org.bitcoinj.base.ScriptType;
 import org.bitcoinj.base.internal.ByteUtils;
 import org.bitcoinj.core.Context;
+import org.bitcoinj.core.TransactionOutPoint;
 import org.bitcoinj.crypto.ECKey;
 import org.bitcoinj.core.NetworkParameters;
 import org.bitcoinj.core.Transaction;
@@ -161,7 +162,7 @@ public class DefaultRiskAnalysisTest {
         // Test non-standard script as an input.
         Transaction tx = new Transaction(MAINNET);
         assertEquals(DefaultRiskAnalysis.RuleViolation.NONE, DefaultRiskAnalysis.isStandard(tx));
-        tx.addInput(new TransactionInput(null, nonStandardScript));
+        tx.addInput(new TransactionInput(null, nonStandardScript, TransactionOutPoint.UNCONNECTED));
         assertEquals(DefaultRiskAnalysis.RuleViolation.SHORTEST_POSSIBLE_PUSHDATA, DefaultRiskAnalysis.isStandard(tx));
         // Test non-standard script as an output.
         tx.clearInputs();
@@ -175,15 +176,14 @@ public class DefaultRiskAnalysisTest {
         TransactionSignature sig = TransactionSignature.dummy();
         Script scriptOk = ScriptBuilder.createInputScript(sig);
         assertEquals(RuleViolation.NONE,
-                DefaultRiskAnalysis.isInputStandard(new TransactionInput(null, scriptOk.getProgram())));
+                DefaultRiskAnalysis.isInputStandard(new TransactionInput(null, scriptOk.getProgram(), TransactionOutPoint.UNCONNECTED)));
 
         byte[] sigBytes = sig.encodeToBitcoin();
         // Appending a zero byte makes the signature uncanonical without violating DER encoding.
         Script scriptUncanonicalEncoding = new ScriptBuilder().data(Arrays.copyOf(sigBytes, sigBytes.length + 1))
                 .build();
-        assertEquals(RuleViolation.SIGNATURE_CANONICAL_ENCODING,
+        assertEquals(RuleViolation.SIGNATURE_CANONICAL_ENCODING, DefaultRiskAnalysis.isInputStandard(
-                DefaultRiskAnalysis.isInputStandard(new TransactionInput(null, scriptUncanonicalEncoding
+                new TransactionInput(null, scriptUncanonicalEncoding.getProgram(), TransactionOutPoint.UNCONNECTED)));
-                        .getProgram())));
     }
 
     @Test
@@ -192,8 +192,8 @@ public class DefaultRiskAnalysisTest {
         TransactionSignature sig = TransactionSignature.dummy();
         Script scriptHighS = ScriptBuilder
                 .createInputScript(new TransactionSignature(sig.r, ECKey.CURVE.getN().subtract(sig.s)));
-        assertEquals(RuleViolation.SIGNATURE_CANONICAL_ENCODING,
+        assertEquals(RuleViolation.SIGNATURE_CANONICAL_ENCODING, DefaultRiskAnalysis.isInputStandard(
-                DefaultRiskAnalysis.isInputStandard(new TransactionInput(null, scriptHighS.getProgram())));
+                new TransactionInput(null, scriptHighS.getProgram(), TransactionOutPoint.UNCONNECTED)));
 
         // This is a real transaction. Its signatures S component is "low".
         Transaction tx1 = new Transaction(MAINNET, ByteBuffer.wrap(ByteUtils.parseHex(

core/src/test/java/org/bitcoinj/wallet/WalletTest.java

@@ -751,7 +751,8 @@ public class WalletTest extends TestWithWallet {
         TransactionOutput to = createMock(TransactionOutput.class);
         EasyMock.expect(to.isAvailableForSpending()).andReturn(true);
         EasyMock.expect(to.isMineOrWatched(wallet)).andReturn(true);
-        EasyMock.expect(to.getSpentBy()).andReturn(new TransactionInput(null, new byte[0]));
+        EasyMock.expect(to.getSpentBy()).andReturn(
+                new TransactionInput(null, new byte[0], TransactionOutPoint.UNCONNECTED));
 
         Transaction tx = FakeTxBuilder.createFakeTxWithoutChange(TESTNET, to);
 

integration-test/src/test/java/org/bitcoinj/core/PeerTest.java

@@ -824,7 +824,7 @@ public class PeerTest extends TestWithNetworkConnections {
         });
         connect();
         Transaction t1 = new Transaction(TESTNET);
-        t1.addInput(new TransactionInput(t1, new byte[]{}));
+        t1.addInput(new TransactionInput(t1, new byte[0], TransactionOutPoint.UNCONNECTED));
         t1.addOutput(COIN, new ECKey().toAddress(ScriptType.P2PKH, BitcoinNetwork.TESTNET));
         Transaction t2 = new Transaction(TESTNET);
         t2.addInput(t1.getOutput(0));