/**
* Calculate the hash of the current transaction, when you are looking to
* spend $txOut, and are signing $inputToSign. The SigHashType defaults to
* SIGHASH_ALL, though SIGHASH_SINGLE, SIGHASH_NONE, SIGHASH_ANYONECANPAY
* can be used.
*
* @param ScriptInterface $txOutScript
* @param $inputToSign
* @param int $sighashType
* @return Buffer
* @throws \Exception
*/
public function calculate(ScriptInterface $txOutScript, $inputToSign, $sighashType = SignatureHashInterface::SIGHASH_ALL)
{
$copy = $this->transaction->makeCopy();
$inputs = $copy->getInputs();
$outputs = $copy->getOutputs();
if ($inputToSign > count($inputs)) {
throw new \Exception('Input does not exist');
}
// Default SIGHASH_ALL procedure: null all input scripts
$inputCount = count($inputs);
for ($i = 0; $i < $inputCount; $i++) {
$inputs->getInput($i)->setScript(new Script());
}
$inputs->getInput($inputToSign)->setScript($txOutScript);
$math = Bitcoin::getMath();
if ($math->bitwiseAnd($sighashType, 31) == SignatureHashInterface::SIGHASH_NONE) {
// Set outputs to empty vector, and set sequence number of inputs to 0.
$copy->setOutputs(new TransactionOutputCollection());
// Let the others update at will. Set sequence of inputs we're not signing to 0.
$inputCount = count($inputs);
for ($i = 0; $i < $inputCount; $i++) {
if ($math->cmp($i, $inputToSign) !== 0) {
$inputs->getInput($i)->setSequence(0);
}
}
} elseif ($math->bitwiseAnd($sighashType, 31) == SignatureHashInterface::SIGHASH_SINGLE) {
// Resize output array to $inputToSign + 1, set remaining scripts to null,
// and set sequence's to zero.
$nOutput = $inputToSign;
if ($math->cmp($nOutput, count($outputs)) >= 0) {
return Buffer::hex('0100000000000000000000000000000000000000000000000000000000000000');
}
// Resize..
$outputs = $outputs->slice(0, $nOutput + 1)->getOutputs();
// Set to null
for ($i = 0; $i < $nOutput; $i++) {
$outputs[$i] = new TransactionOutput($math->getBinaryMath()->getTwosComplement(-1, 64), new Script());
}
$copy->setOutputs(new TransactionOutputCollection($outputs));
// Let the others update at will. Set sequence of inputs we're not signing to 0.
$inputCount = count($inputs);
for ($i = 0; $i < $inputCount; $i++) {
if ($math->cmp($i, $inputToSign) != 0) {
$inputs->getInput($i)->setSequence(0);
}
}
}
// This can happen regardless of whether it's ALL, NONE, or SINGLE
if ($math->bitwiseAnd($sighashType, SignatureHashInterface::SIGHASH_ANYONECANPAY)) {
$input = $inputs->getInput($inputToSign);
$copy->setInputs(new TransactionInputCollection([$input]));
}
// Serialize the TxCopy and append the 4 byte hashtype (little endian);
$txParser = new Parser($copy->getBuffer());
$txParser->writeInt(4, $sighashType, true);
return Hash::sha256d($txParser->getBuffer());
}
