/// <summary>Adds a command to the write list of this transaction</summary>
/// <remarks>Must be called with m_lock taken</remarks>
private void AddWriteCommand_NeedsLocking(WriteCommand command)
{
var commands = new WriteCommand[1];
commands[0] = command;
if (!m_writes.GetOrAdd(command.Key, commands, out commands))
{ // there is already a command for that key
if (command.Type == Operation.Set)
{ // Set always overwrites everything
if (commands.Length == 1)
{ // reuse the command array
commands[0] = command;
return;
}
// overwrite
m_writes.SetItem(command.Key, new[] { command });
return;
}
var last = commands[commands.Length - 1];
if (last.Type == Operation.Set)
{ // "SET(X) x ATOMIC(op, P)" are merged into "SET(X')" with X' = atomic(op, X, P)
Contract.Assert(commands.Length == 1);
command = WriteCommand.MergeSetAndAtomicOperation(last, command.Type, command.Value);
// update in place
commands[commands.Length - 1] = command;
return;
}
if (last.Type == command.Type)
{ // atomics of the same kind can be merged
command = WriteCommand.MergeTwoAtomicOperations(last, command.Value);
// update in place
commands[commands.Length - 1] = command;
return;
}
// just queue the command at the end
Array.Resize <WriteCommand>(ref commands, commands.Length + 1);
commands[commands.Length - 1] = command;
m_writes.SetItem(command.Key, commands);
}
}
