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Add comments on dust output values and constants/util to calc them

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Matt Corallo 2013-05-17 14:42:44 +02:00 committed by Mike Hearn
parent 4b1e45fae2
commit 86046b7122
3 changed files with 47 additions and 1 deletions
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9
core/src/main/java/com/google/bitcoin/core/Transaction.java
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@ -57,6 +57,15 @@ public class Transaction extends ChildMessage implements Serializable {
/** How many bytes a transaction can be before it won't be relayed anymore. */
public static final int MAX_STANDARD_TX_SIZE = 100 * 1024;
/** If fee is lower than this value (in satoshis), a default reference client will treat it as if there were no fee */
public static final BigInteger REFERENCE_DEFAULT_MIN_TX_FEE = BigInteger.valueOf(10000);
/**
* Any standard (ie pay-to-address) output smaller than this value (in satoshis) will most likely be rejected by the network.
* This is calculated by assuming a standard output will be 34 bytes, and then using the formula used in
* {@link TransactionOutput#getMinNonDustValue(BigInteger)}.
*/
public static final BigInteger MIN_NONDUST_OUTPUT = BigInteger.valueOf(5461);
// These are serialized in both bitcoin and java serialization.
private long version;

13
core/src/main/java/com/google/bitcoin/core/TransactionOutput.java
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@ -172,6 +172,19 @@ public class TransactionOutput extends ChildMessage implements Serializable {
throw new RuntimeException("Output linked to wrong parent transaction?");
}
/**
* Gets the minimum value for a txout of this size to be considered non-dust by a reference client (and thus relayed).
* See: CTxOut::IsDust() in the reference client.
*
* @param feePerKbRequired The fee required per kilobyte. Note that this is the same as the reference client's -minrelaytxfee * 3
* If you want a safe default, use {@link Transaction#REFERENCE_DEFAULT_MIN_TX_FEE}*3
*/
public BigInteger getMinNonDustValue(BigInteger feePerKbRequired) {
// Note we skip the *3 as that should be considered in the parameter and we add one to account for loss of precision
// (1/1000 chance we require too much fee, 999/1000 chance we get the exact right value...)
return feePerKbRequired.multiply(BigInteger.valueOf(this.bitcoinSerialize().length + 148)).divide(BigInteger.valueOf(1000)).add(BigInteger.ONE);
}
/**
* Sets this objects availableForSpending flag to false and the spentBy pointer to the given input.
* If the input is null, it means this output was signed over to somebody else rather than one of our own keys.

26
core/src/main/java/com/google/bitcoin/core/Wallet.java
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@ -1650,7 +1650,11 @@ public class Wallet implements Serializable, BlockChainListener {
/**
* A transaction, probably incomplete, that describes the outline of what you want to do. This typically will
* mean it has some outputs to the intended destinations, but no inputs or change address (and therefore no
* fees) - the wallet will calculate all that for you and update tx later.
* fees) - the wallet will calculate all that for you and update tx later.</p>
*
* <p>Be careful when adding outputs that you check the min output value
* ({@link TransactionOutput#getMinNonDustValue(BigInteger)}) to avoid the whole transaction being rejected
* because one output is dust.</p>
*/
public Transaction tx;
@ -1683,6 +1687,12 @@ public class Wallet implements Serializable, BlockChainListener {
private SendRequest() {}
/**
* <p>Creates a new SendRequest to the given address for the given value.</p>
*
* <p>Be very careful when value is smaller than {@link Transaction#MIN_NONDUST_OUTPUT} as the transaction will
* likely be rejected by the network in this case.</p>
*/
public static SendRequest to(Address destination, BigInteger value) {
SendRequest req = new Wallet.SendRequest();
req.tx = new Transaction(destination.getParameters());
@ -1690,6 +1700,14 @@ public class Wallet implements Serializable, BlockChainListener {
return req;
}
/**
* <p>Creates a new SendRequest to the given pubkey for the given value.</p>
*
* <p>Be careful to check the output's value is reasonable using
* {@link TransactionOutput#getMinNonDustValue(BigInteger)} afterwards or you risk having the transaction
* rejected by the network. Note that using {@link SendRequest#to(Address, java.math.BigInteger)} will result
* in a smaller output, and thus the ability to use a smaller output value without rejection.</p>
*/
public static SendRequest to(NetworkParameters params, ECKey destination, BigInteger value) {
SendRequest req = new SendRequest();
req.tx = new Transaction(params);
@ -1723,6 +1741,9 @@ public class Wallet implements Serializable, BlockChainListener {
* prevent this, but that should only occur once the transaction has been accepted by the network. This implies
* you cannot have more than one outstanding sending tx at once.</p>
*
* <p>You MUST ensure that nanocoins is smaller than {@link Transaction#MIN_NONDUST_OUTPUT} or the transaction will
* almost certainly be rejected by the network as dust.</p>
*
* @param address The Bitcoin address to send the money to.
* @param nanocoins How much currency to send, in nanocoins.
* @return either the created Transaction or null if there are insufficient coins.
@ -1771,6 +1792,9 @@ public class Wallet implements Serializable, BlockChainListener {
* successfully broadcast. This means that even if the network hasn't heard about your transaction you won't be
* able to spend those same coins again.</p>
*
* <p>You MUST ensure that value is smaller than {@link Transaction#MIN_NONDUST_OUTPUT} or the transaction will
* almost certainly be rejected by the network as dust.</p>
*
* @param peerGroup a PeerGroup to use for broadcast or null.
* @param to Which address to send coins to.
* @param value How much value to send. You can use Utils.toNanoCoins() to calculate this.