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TransactionOutput: Fix fee calculation in getMinNonDustValue().

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Adds a test, too.
This commit is contained in:
Andreas Schildbach
2016-03-12 21:07:45 +01:00
parent 90d8c151be
commit 0bc6c04d5f
2 changed files with 10 additions and 6 deletions
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10
core/src/main/java/org/bitcoinj/core/TransactionOutput.java
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@@ -225,23 +225,21 @@ public class TransactionOutput extends ChildMessage {
* <p>You probably should use {@link org.bitcoinj.core.TransactionOutput#getMinNonDustValue()} which uses
* a safe fee-per-kb by default.</p>
*
* @param feePerKbRequired The fee required per kilobyte. Note that this is the same as Bitcoin Core's -minrelaytxfee * 3
* If you want a safe default, use {@link Transaction#REFERENCE_DEFAULT_MIN_TX_FEE}*3
* @param feePerKb The fee required per kilobyte. Note that this is the same as Bitcoin Core's -minrelaytxfee * 3
*/
public Coin getMinNonDustValue(Coin feePerKbRequired) {
public Coin getMinNonDustValue(Coin feePerKb) {
// A typical output is 33 bytes (pubkey hash + opcodes) and requires an input of 148 bytes to spend so we add
// that together to find out the total amount of data used to transfer this amount of value. Note that this
// formula is wrong for anything that's not a pay-to-address output, unfortunately, we must follow Bitcoin Core's
// wrongness in order to ensure we're considered standard. A better formula would either estimate the
// size of data needed to satisfy all different script types, or just hard code 33 below.
final long size = this.unsafeBitcoinSerialize().length + 148;
Coin[] nonDustAndRemainder = feePerKbRequired.multiply(size).divideAndRemainder(1000);
return nonDustAndRemainder[1].equals(Coin.ZERO) ? nonDustAndRemainder[0] : nonDustAndRemainder[0].add(Coin.SATOSHI);
return feePerKb.multiply(size).divide(1000);
}
/**
* Returns the minimum value for this output to be considered "not dust", i.e. the transaction will be relayable
* and mined by default miners. For normal pay to address outputs, this is 546 satoshis, the same as
* and mined by default miners. For normal pay to address outputs, this is 2730 satoshis, the same as
* {@link Transaction#MIN_NONDUST_OUTPUT}.
*/
public Coin getMinNonDustValue() {

6
core/src/test/java/org/bitcoinj/core/TransactionOutputTest.java
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@@ -64,4 +64,10 @@ public class TransactionOutputTest extends TestWithWallet {
assertNull(tx.getOutput(0).getAddressFromP2SH(PARAMS));
assertNull(tx.getOutput(0).getAddressFromP2PKHScript(PARAMS));
}
@Test
public void getMinNonDustValue() throws Exception {
TransactionOutput payToAddressOutput = new TransactionOutput(PARAMS, null, Coin.COIN, myAddress);
assertEquals(Transaction.MIN_NONDUST_OUTPUT, payToAddressOutput.getMinNonDustValue());
}
}