/// <summary>
/// Obtains order number of the last saved rewind state in the database.
/// </summary>
/// <param name="transaction">Open dBreeze transaction.</param>
/// <returns>Order number of the last saved rewind state, or <c>0</c> if no rewind state is found in the database.</returns>
/// <remarks>
/// TODO: Using <c>0</c> is hacky here, and <see cref="SaveChanges" /> exploits that in a way that if no such rewind
/// data exist
/// the order number of the first rewind data is 0 + 1 = 1.
/// </remarks>
int GetRewindIndex(Transaction transaction)
{
var prevLazySettings = transaction.ValuesLazyLoadingIsOn;
transaction.ValuesLazyLoadingIsOn = true;
var firstRow = transaction.SelectBackward <int, byte[]>("Rewind").FirstOrDefault();
transaction.ValuesLazyLoadingIsOn = prevLazySettings;
return(firstRow != null ? firstRow.Key : 0);
}
/// <summary>
/// Obtains order number of the last saved rewind state in the database.
/// </summary>
/// <param name="transaction">Open DBreeze transaction.</param>
/// <returns>Order number of the last saved rewind state, or <c>-1</c> if no rewind state is found in the database.</returns>
/// <remarks>TODO: Using <c>-1</c> is hacky here, and <see cref="SaveChangesAsync"/> exploits that in a way that if no such rewind data exist
/// the order number of the first rewind data is -1 + 1 = 0.</remarks>
private int GetRewindIndex(DBreeze.Transactions.Transaction transaction)
{
bool prevLazySettings = transaction.ValuesLazyLoadingIsOn;
transaction.ValuesLazyLoadingIsOn = true;
Row <int, RewindData> firstRow = transaction.SelectBackward <int, RewindData>("Rewind").FirstOrDefault();
transaction.ValuesLazyLoadingIsOn = prevLazySettings;
return(firstRow != null ? firstRow.Key : -1);
}
/// <inheritdoc />
public override Task <uint256> Rewind()
{
Task <uint256> task = Task.Run(() =>
{
this.logger.LogTrace("()");
uint256 res = null;
using (DBreeze.Transactions.Transaction transaction = this.dbreeze.GetTransaction())
{
transaction.SynchronizeTables("BlockHash", "Coins", "Rewind");
if (this.GetRewindIndex(transaction) == -1)
{
transaction.RemoveAllKeys("Coins", true);
this.SetBlockHash(transaction, this.network.GenesisHash);
res = this.network.GenesisHash;
}
else
{
transaction.ValuesLazyLoadingIsOn = false;
Row <int, RewindData> firstRow = transaction.SelectBackward <int, RewindData>("Rewind").FirstOrDefault();
transaction.RemoveKey("Rewind", firstRow.Key);
this.SetBlockHash(transaction, firstRow.Value.PreviousBlockHash);
foreach (uint256 txId in firstRow.Value.TransactionsToRemove)
{
this.logger.LogTrace("Outputs of transaction ID '{0}' will be removed.", txId);
transaction.RemoveKey("Coins", txId.ToBytes(false));
}
foreach (UnspentOutputs coin in firstRow.Value.OutputsToRestore)
{
this.logger.LogTrace("Outputs of transaction ID '{0}' will be restored.", coin.TransactionId);
transaction.Insert("Coins", coin.TransactionId.ToBytes(false), coin.ToCoins());
}
res = firstRow.Value.PreviousBlockHash;
}
transaction.Commit();
}
this.logger.LogTrace("(-):'{0}'", res);
return(res);
});
return(task);
}
/// <inheritdoc />
public uint256 Rewind()
{
uint256 res = null;
using (DBreeze.Transactions.Transaction transaction = this.CreateTransaction())
{
transaction.SynchronizeTables("BlockHash", "Coins", "Rewind");
if (this.GetRewindIndex(transaction) == 0)
{
transaction.RemoveAllKeys("Coins", true);
this.SetBlockHash(transaction, this.network.GenesisHash);
res = this.network.GenesisHash;
}
else
{
transaction.ValuesLazyLoadingIsOn = false;
Row <int, byte[]> firstRow = transaction.SelectBackward <int, byte[]>("Rewind").FirstOrDefault();
transaction.RemoveKey("Rewind", firstRow.Key);
var rewindData = this.dBreezeSerializer.Deserialize <RewindData>(firstRow.Value);
this.SetBlockHash(transaction, rewindData.PreviousBlockHash);
foreach (uint256 txId in rewindData.TransactionsToRemove)
{
this.logger.LogDebug("Outputs of transaction ID '{0}' will be removed.", txId);
transaction.RemoveKey("Coins", txId.ToBytes(false));
}
foreach (UnspentOutputs coin in rewindData.OutputsToRestore)
{
this.logger.LogDebug("Outputs of transaction ID '{0}' will be restored.", coin.TransactionId);
transaction.Insert("Coins", coin.TransactionId.ToBytes(false), this.dBreezeSerializer.Serialize(coin.ToCoins()));
}
res = rewindData.PreviousBlockHash;
}
transaction.Commit();
}
return(res);
}
public byte[] GetLast(DBreeze.Transactions.Transaction dbTx)
{
var record = dbTx.SelectBackward <uint, byte[]>(TABLE).First();
return(record == null ? null : record.Value);
}
