public IObservable<DataBlock> ReadBlocksFromFile(string filename)
{
var obs = Observable.Create<DataBlock>(async (subject, token) =>
{
try
{
using (var stream = File.Open(filename, FileMode.Open, FileAccess.Read))
{
using (var reader = new StreamReader(stream))
{
DataBlock prev = null;
while (!reader.EndOfStream)
{
if (token.IsCancellationRequested)
break;
var block = new DataBlock(BufferSize);
block.PreviousBlock = prev;
block = await ReadBlockAsync(reader, block);
subject.OnNext(block);
prev = block;
}
subject.OnCompleted();
}
}
} catch (Exception ex)
{
subject.OnError(ex);
}
});
return obs;
}
private async Task<DataBlock> ReadBlockAsync(StreamReader reader, DataBlock target)
{
var readBytes = await reader.ReadAsync(target.Data, 0, BufferSize);
if (readBytes != BufferSize)
{
target.ResizeData(readBytes);
}
return target;
}
public IEnumerable<DataEntry> Refine(DataBlock source)
{
if (_lastEol == null)
{
_lastEol = new EndOfLine(source);
_lastEol.RelativePosition = 0;
}
foreach(var eol in FindLineEnds(source))
{
yield return Build(eol);
_lastEol = eol;
}
}
private List<DataBlock> FindLast(DataBlock start)
{
var p = start;
var buffer = new Stack<DataBlock>();
while(p != _lastEol.Block)
{
buffer.Push(p);
if (p.PreviousBlock == null)
{
return buffer.ToList();
}
p = p.PreviousBlock;
}
buffer.Push(p);
return buffer.ToList();
}
private IEnumerable<EndOfLine> FindLineEnds(DataBlock block)
{
var currentResult = new EndOfLine(block);
for(int currentPos = 0; currentPos < block.Length; currentPos++)
{
if (block.Data[currentPos] == EndOfLine.LineFeed)
{
currentResult.RelativePosition = currentPos;
yield return currentResult;
currentResult = new EndOfLine(block);
}
if (block.Data[currentPos] == EndOfLine.CarriageReturn)
{
currentResult.IsWindowsEndOfLine = true;
}
}
yield break;
}
public EndOfLine(DataBlock b)
{
Block = b;
RelativePosition = Unknown;
IsWindowsEndOfLine = false;
}
