/// <summary>
/// Returns estimated value for the final signed transaction.
/// </summary>
/// <param name="inputCount">Number of inputs to spend</param>
/// <param name="outputCount">Number of outputs to receive</param>
/// <returns>Transaction size</returns>
public static int GetTransactionSize(int inputCount, int outputCount)
{
int c1 = NumberConversions.MakeCompactSize((UInt64)inputCount).Length / 2;
int c2 = NumberConversions.MakeCompactSize((UInt64)outputCount).Length / 2;
int inputSize =
32 //TX hash
+ 4 //output Index
+ 1 //scriptSig length
+ 138 //scriptSig sig
+ 4; //sequence
int outputSize =
8 //Amount
+ 1 //pk_script length
+ 25; //pk_script
int totalSize =
4 //Version
+ c1 //TxIn Count
+ inputSize * inputCount
+ c2 //TxOut Count
+ outputSize * outputCount
+ 4; //LockTime
return((totalSize <= 10) ? 0 : totalSize);
}
/// <summary>
/// Creates a Raw Unsigned bitcoin transaction Transaction.
/// <para/> Sources:
/// <para/> 1. https://bitcoin.stackexchange.com/questions/32628/redeeming-a-raw-transaction-step-by-step-example-required
/// <para/> 2. https://bitcoin.org/en/developer-reference#raw-transaction-format
/// <para/> 3. https://bitcoin.org/en/developer-examples#simple-raw-transaction
/// </summary>
/// <param name="txToSpend">List of UTXOs to spend.</param>
/// <param name="receiveAddr">List of receiving addresses and the amount to be paid to each.</param>
/// <param name="wallet">Type of the wallet (Electrum does not recognize normal type of scriptSig placeholder).</param>
/// <returns>Rat unsigned transaction string.</returns>
public static string CreateRawTx(List <UTXO> txToSpend, List <ReceivingAddress> receiveAddr, UInt32 lockTime, WalletType wallet)
{
StringBuilder rawTx = new StringBuilder();
// 1) 4 byte - version
UInt32 version = 1;
rawTx.Append(NumberConversions.IntToHex(version, 4));
// 2) ? byte - tx_in count (compactSize uint)
int txInCount = txToSpend.Count;
rawTx.Append(NumberConversions.MakeCompactSize((UInt64)txInCount));
for (int i = 0; i < txInCount; i++)
{
// 3) 32 byte - TX hash (reverse)
string txToSend = txToSpend[i].TxHash;
rawTx.Append(ReverseTx(txToSend));
// 4) 4 byte - output Index
UInt32 outputIndex = txToSpend[i].OutIndex;
rawTx.Append(NumberConversions.IntToHex(outputIndex, 4));
// 5) ? byte - scriptSig length (compactSize uint) (Maximum value is 10,000 bytes)
// Can be from 0 and up. Will be replaced by actual scriptSig with another length.
// Format can be different based on the client which will be used for signing.
if (string.IsNullOrEmpty(txToSpend[i].AddressHash160) && wallet != WalletType.Core)
{
throw new Exception(string.Format("No address was found. Set wallet type to Core."));
}
string scriptSig = BuildScript(txToSpend[i].AddressHash160, wallet);
rawTx.Append(NumberConversions.IntToHex((UInt64)(scriptSig.Length / 2), 1));
// 6) ? byte - scriptSig which is filled with scriptPubkey temporarily (20 is half the length of address hash160)
rawTx.Append(scriptSig);
//7) 4 byte - sequence - max is 0xffffffff - can change for RBF transactions
// Ref:
// https://bitcoin.stackexchange.com/questions/2025/what-is-txins-sequence
UInt32 sequence = UInt32.MaxValue;
rawTx.Append(NumberConversions.IntToHex(sequence, 4));
}
//8) ? byte - tx_out count (compactSize uint)
int txOutCount = receiveAddr.Count;
rawTx.Append(NumberConversions.MakeCompactSize((UInt64)txOutCount));
foreach (var item in receiveAddr)
{
//9) 8 byte - amout to transfer
UInt64 amount = item.PaymentSatoshi;
rawTx.Append(NumberConversions.IntToHex(amount, 8));
//10) ? byte - pk_script length (compactSize uint)
string itemHash = BitcoinConversions.Base58ToHash160(item.Address);
string outputScript = BuildScript(itemHash, WalletType.Normal);
rawTx.Append(NumberConversions.MakeCompactSize((UInt64)outputScript.Length / 2));
//11) ? byte - pk_script
rawTx.Append(outputScript);
}
//12) 4 byte - lock time
// * If less than 500 million, locktime is parsed as a block height. The transaction can be added to any block which has this height or higher.
// * If greater than or equal to 500 million, locktime is parsed using the Unix epoch time format (the number of seconds elapsed since 1970-01-01T00:00 UTC—currently over 1.395 billion). The transaction can be added to any block whose block time is greater than the locktime.
rawTx.Append(NumberConversions.IntToHex(lockTime, 4));
return(rawTx.ToString());
}