private bool ConnectInputs(ref CTransaction tx, ref Dictionary<COutPoint, TxOutItem> inputs, ref Dictionary<COutPoint, TxOutItem> queued, ref CBlockStoreItem cursorBlock, bool fBlock, bool fScriptChecks, scriptflag scriptFlags)
{
// Take over previous transactions' spent items
// fBlock is true when this is called from AcceptBlock when a new best-block is added to the blockchain
if (!tx.IsCoinBase)
{
long nValueIn = 0;
long nFees = 0;
for (uint i = 0; i < tx.vin.Length; i++)
{
var prevout = tx.vin[i].prevout;
Contract.Assert(inputs.ContainsKey(prevout));
var input = inputs[prevout];
CBlockStoreItem parentBlockCursor;
if (input.nMerkleNodeID == -1)
{
// This input seems as is confirmed by the same block.
if (!queued.ContainsKey(prevout))
{
return false; // No such output has been queued by this block.
}
// TODO: Ensure that neither coinbase nor coinstake outputs are
// available for spending in the generation block.
}
else
{
// This input has been confirmed by one of the earlier accepted blocks.
var merkleItem = GetMerkleCursor(input, out parentBlockCursor);
if (merkleItem == null)
{
return false; // Unable to find merkle node
}
// If prev is coinbase or coinstake, check that it's matured
if (merkleItem.IsCoinBase || merkleItem.IsCoinStake)
{
if (cursorBlock.nHeight - parentBlockCursor.nHeight < NetInfo.nGeneratedMaturity)
{
return false; // tried to spend non-matured generation input.
}
}
// check transaction timestamp
if (merkleItem.nTime > tx.nTime)
{
return false; // transaction timestamp earlier than input transaction
}
}
// Check for negative or overflow input values
nValueIn += input.nValue;
if (!CTransaction.MoneyRange(input.nValue) || !CTransaction.MoneyRange(nValueIn))
{
return false; // txin values out of range
}
}
// The first loop above does all the inexpensive checks.
// Only if ALL inputs pass do we perform expensive ECDSA signature checks.
// Helps prevent CPU exhaustion attacks.
for (int i = 0; i < tx.vin.Length; i++)
{
var prevout = tx.vin[i].prevout;
Contract.Assert(inputs.ContainsKey(prevout));
var input = inputs[prevout];
// Check for conflicts (double-spend)
if (input.IsSpent)
{
return false;
}
// Skip ECDSA signature verification when connecting blocks (fBlock=true)
// before the last blockchain checkpoint. This is safe because block merkle hashes are
// still computed and checked, and any change will be caught at the next checkpoint.
if (fScriptChecks)
{
// Verify signature
if (!ScriptCode.VerifyScript(tx.vin[i].scriptSig, input.scriptPubKey, tx, i, (int)scriptflag.SCRIPT_VERIFY_P2SH, 0))
{
return false; // VerifyScript failed.
}
}
// Mark outpoint as spent
input.IsSpent = true;
inputs[prevout] = input;
// Write back
if (fBlock)
{
if (input.nMerkleNodeID != -1)
{
// Input has been confirmed earlier.
queued.Add(prevout, input);
}
else
{
// Input has been confirmed by current block.
queued[prevout] = input;
}
}
}
if (tx.IsCoinStake)
{
if (HashCheckpoints.LastCheckpointTime < tx.nTime)
{
// Coin stake tx earns reward instead of paying fee
long nCoinAge;
if (!tx.GetCoinAge(ref inputs, out nCoinAge))
{
return false; // unable to get coin age for coinstake
}
long nReward = tx.nValueOut - nValueIn;
long nCalculatedReward = CBlock.GetProofOfStakeReward(nCoinAge, cursorBlock.nBits, tx.nTime) - tx.GetMinFee(1, false, CTransaction.MinFeeMode.GMF_BLOCK) + CTransaction.nCent;
if (nReward > nCalculatedReward)
{
return false; // coinstake pays too much
}
}
}
else
{
if (nValueIn < tx.nValueOut)
{
return false; // value in < value out
}
// Tally transaction fees
long nTxFee = nValueIn - tx.nValueOut;
if (nTxFee < 0)
{
return false; // nTxFee < 0
}
nFees += nTxFee;
if (!CTransaction.MoneyRange(nFees))
{
return false; // nFees out of range
}
}
}
return true;
}
