/// <summary>
/// Creates a transaction that sends $coins.$cents BTC to the given address.
/// </summary>
/// <remarks>
/// IMPORTANT: This method does NOT update the wallet. If you call createSend again you may get two transactions
/// that spend the same coins. You have to call confirmSend on the created transaction to 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.
/// </remarks>
/// <param name="address">The BitCoin address to send the money to.</param>
/// <param name="nanocoins">How much currency to send, in nanocoins.</param>
/// <param name="changeAddress">
/// Which address to send the change to, in case we can't make exactly the right value from
/// our coins. This should be an address we own (is in the keychain).
/// </param>
/// <returns>
/// A new <see cref="Transaction"/> or null if we cannot afford this send.
/// </returns>
internal Transaction CreateSend(Address address, ulong nanocoins, Address changeAddress)
{
lock (this)
{
_log.Info("Creating send tx to " + address + " for " +
Utils.BitcoinValueToFriendlyString(nanocoins));
// To send money to somebody else, we need to do gather up transactions with unspent outputs until we have
// sufficient value. Many coin selection algorithms are possible, we use a simple but suboptimal one.
// TODO: Sort coins so we use the smallest first, to combat wallet fragmentation and reduce fees.
var valueGathered = 0UL;
var gathered = new LinkedList<TransactionOutput>();
foreach (var tx in Unspent.Values)
{
foreach (var output in tx.Outputs)
{
if (!output.IsAvailableForSpending) continue;
if (!output.IsMine(this)) continue;
gathered.AddLast(output);
valueGathered += output.Value;
}
if (valueGathered >= nanocoins) break;
}
// Can we afford this?
if (valueGathered < nanocoins)
{
_log.Info("Insufficient value in wallet for send, missing " +
Utils.BitcoinValueToFriendlyString(nanocoins - valueGathered));
// TODO: Should throw an exception here.
return null;
}
Debug.Assert(gathered.Count > 0);
var sendTx = new Transaction(_params);
sendTx.AddOutput(new TransactionOutput(_params, sendTx, nanocoins, address));
var change = (long) (valueGathered - nanocoins);
if (change > 0)
{
// The value of the inputs is greater than what we want to send. Just like in real life then,
// we need to take back some coins ... this is called "change". Add another output that sends the change
// back to us.
_log.Info(" with " + Utils.BitcoinValueToFriendlyString((ulong) change) + " coins change");
sendTx.AddOutput(new TransactionOutput(_params, sendTx, (ulong) change, changeAddress));
}
foreach (var output in gathered)
{
sendTx.AddInput(output);
}
// Now sign the inputs, thus proving that we are entitled to redeem the connected outputs.
sendTx.SignInputs(Transaction.SigHash.All, this);
_log.InfoFormat(" created {0}", sendTx.HashAsString);
return sendTx;
}
}
/// <summary>
/// Sends coins to the given address, via the given <see cref="Peer"/>.
/// Change is returned to the first key in the wallet.
/// </summary>
/// <param name="peer">The peer to send via.</param>
/// <param name="to">Which address to send coins to.</param>
/// <param name="nanocoins">How many nanocoins to send. You can use Utils.ToNanoCoins() to calculate this.</param>
/// <returns>The <see cref="Transaction"/> that was created or null if there was insufficient balance to send the coins.</returns>
/// <exception cref="IOException">If there was a problem broadcasting the transaction.</exception>
public Transaction SendCoins(Peer peer, Address to, ulong nanocoins)
{
lock (this)
{
var tx = CreateSend(to, nanocoins);
if (tx == null) // Not enough money! :-(
return null;
peer.BroadcastTransaction(tx);
ConfirmSend(tx);
return tx;
}
}
/// <summary>
/// Statelessly creates a transaction that sends the given number of nanocoins to address. The change is sent to
/// the first address in the wallet, so you must have added at least one key.
/// </summary>
/// <remarks>
/// This method is stateless in the sense that calling it twice with the same inputs will result in two
/// Transaction objects which are equal. The wallet is not updated to track its pending status or to mark the
/// coins as spent until confirmSend is called on the result.
/// </remarks>
internal Transaction CreateSend(Address address, ulong nanocoins)
{
lock (this)
{
// For now let's just pick the first key in our keychain. In future we might want to do something else to
// give the user better privacy here, eg in incognito mode.
Debug.Assert(Keychain.Count > 0, "Can't send value without an address to use for receiving change");
var first = Keychain[0];
return CreateSend(address, nanocoins, first.ToAddress(_params));
}
}
/// <summary>
/// Sends coins to the given address, via the given <see cref="PeerGroup"/>.
/// Change is returned to the first key in the wallet.
/// </summary>
/// <param name="peerGroup">The peer group to send via.</param>
/// <param name="to">Which address to send coins to.</param>
/// <param name="nanocoins">How many nanocoins to send. You can use Utils.toNanoCoins() to calculate this.</param>
/// <returns>
/// The <see cref="Transaction"/> that was created or null if there was insufficient balance to send the coins.
/// </returns>
/// <exception cref="IOException">If there was a problem broadcasting the transaction.</exception>
public Transaction SendCoins(PeerGroup peerGroup, Address to, ulong nanocoins)
{
lock (this)
{
var tx = CreateSend(to, nanocoins);
if (tx == null) // Not enough money! :-(
return null;
if (!peerGroup.BroadcastTransaction(tx))
{
throw new IOException("Failed to broadcast tx to all connected peers");
}
// TODO - retry logic
ConfirmSend(tx);
return tx;
}
}
internal static byte[] CreateOutputScript(Address to)
{
using (var bits = new MemoryStream())
{
// TODO: Do this by creating a Script *first* then having the script reassemble itself into bytes.
bits.Write(OpDup);
bits.Write(OpHash160);
WriteBytes(bits, to.Hash160);
bits.Write(OpEqualVerify);
bits.Write(OpCheckSig);
return bits.ToArray();
}
}
/// <returns>A human readable version of the transaction useful for debugging.</returns>
public override string ToString()
{
var s = new StringBuilder();
s.Append(" ");
s.Append(HashAsString);
s.AppendLine();
if (IsCoinBase)
{
string script;
string script2;
try
{
script = _inputs[0].ScriptSig.ToString();
script2 = _outputs[0].ScriptPubKey.ToString();
}
catch (ScriptException)
{
script = "???";
script2 = "???";
}
return " == COINBASE TXN (scriptSig " + script + ") (scriptPubKey " + script2 + ")";
}
foreach (var @in in _inputs)
{
s.Append(" ");
s.Append("from ");
try
{
s.Append(@in.ScriptSig.FromAddress.ToString());
}
catch (Exception e)
{
s.Append("[exception: ").Append(e.Message).Append("]");
throw;
}
s.AppendLine();
}
foreach (var @out in _outputs)
{
s.Append(" ");
s.Append("to ");
try
{
var toAddr = new Address(Params, @out.ScriptPubKey.PubKeyHash);
s.Append(toAddr.ToString());
s.Append(" ");
s.Append(Utils.BitcoinValueToFriendlyString(@out.Value));
s.Append(" BTC");
}
catch (Exception e)
{
s.Append("[exception: ").Append(e.Message).Append("]");
}
s.AppendLine();
}
return s.ToString();
}
/// <summary>
/// Returns a solved block that builds on top of this one. This exists for unit tests.
/// </summary>
internal Block CreateNextBlock(Address to, uint time)
{
var b = new Block(Params);
b.DifficultyTarget = _difficultyTarget;
b.AddCoinbaseTransaction(_emptyBytes);
// Add a transaction paying 50 coins to the "to" address.
var t = new Transaction(Params);
t.AddOutput(new TransactionOutput(Params, t, Utils.ToNanoCoins(50, 0), to));
// The input does not really need to be a valid signature, as long as it has the right general form.
var input = new TransactionInput(Params, t, Script.CreateInputScript(_emptyBytes, _emptyBytes));
// Importantly the outpoint hash cannot be zero as that's how we detect a coinbase transaction in isolation
// but it must be unique to avoid 'different' transactions looking the same.
var counter = new byte[32];
counter[0] = (byte) _txCounter++;
input.Outpoint.Hash = new Sha256Hash(counter);
t.AddInput(input);
b.AddTransaction(t);
b.PrevBlockHash = Hash;
b.TimeSeconds = time;
b.Solve();
b.VerifyHeader();
return b;
}
// Visible for testing.
public Block CreateNextBlock(Address to)
{
return CreateNextBlock(to, (uint) UnixTime.ToUnixTime(DateTime.UtcNow));
}