public async Task Extract()
{
TotalWords = (await mRead(64)).GetValueOrDefault();
FileLength?.Invoke(TotalWords);
mMaxHistory = Convert.ToUInt32((await mRead(32)).GetValueOrDefault());
mPresentLength = Convert.ToInt32((await mRead(8)).GetValueOrDefault());
int historyLengthInBits = Log2_WiegleyJ(mMaxHistory - 1) + 1;
while (mWordsWritten < TotalWords)
{
var type = await mRead(1);
if (type == null)
{
throw new EndOfStreamException();
}
if (type.Value == 1)
{
var word = await mRead(8);
if (word == null)
{
throw new EndOfStreamException();
}
await mWrite(word.Value, 8);
mHistory.AddLast(Convert.ToByte(word.Value));
if (mHistory.Count > mMaxHistory)
{
mHistory.RemoveFirst();
}
mWordsWritten++;
WordsWritten?.Invoke(1);
}
else if (type.Value == 0)
{
var offset = await mRead(historyLengthInBits);
var length = await mRead(mPresentLength);
if (offset == null || length == null)
{
throw new EndOfStreamException();
}
if (offset >= mHistory.Count)
{
throw new ArgumentOutOfRangeException(nameof(offset));
}
if (offset < length - 1)
{
throw new ArgumentOutOfRangeException(nameof(length));
}
var pointer = mHistory.Last;
for (int i = 0; i < offset.Value; i++)
{
pointer = pointer.Previous;
}
for (int i = 0; i < length.Value; i++)
{
mHistory.AddLast(pointer.Value);
await mWrite(pointer.Value, 8);
pointer = pointer.Next;
if (mHistory.Count > mMaxHistory)
{
mHistory.RemoveFirst();
}
}
mWordsWritten += length.Value;
WordsWritten?.Invoke(length.Value);
}
else
{
throw new ArgumentOutOfRangeException(nameof(type));
}
}
}