private Stream TryOpenRead(string fileName, out IEmptyReason error)
{
try
{
error = null;
return(_filesystem.Open(fileName, FileMode.Open, FileAccess.Read,
FileShare.ReadWrite | FileShare.Delete));
}
catch (FileNotFoundException e)
{
error = _sourceDoesNotExist;
Log.Debug(e);
}
catch (DirectoryNotFoundException e)
{
error = _sourceDoesNotExist;
Log.Debug(e);
}
catch (UnauthorizedAccessException e)
{
error = _sourceCannotBeAccessed;
Log.Debug(e);
}
catch (IOException e)
{
error = _sourceCannotBeAccessed;
Log.Debug(e);
}
return(null);
}
/// <inheritdoc />
protected override TimeSpan RunOnce(CancellationToken token)
{
bool read = false;
try
{
if (!_filesystem.FileExists(_fileName))
{
SetDoesNotExist();
}
else
{
var info = _filesystem.GetFileInfo(_fileName);
var fileSize = info.Length;
_localProperties.SetValue(Core.Properties.LastModified, info.LastWriteTimeUtc);
_localProperties.SetValue(Core.Properties.Created, info.CreationTimeUtc);
_localProperties.SetValue(Core.Properties.Size, Size.FromBytes(fileSize));
UpdatePercentageProcessed(_lastStreamPosition, fileSize, allow100Percent: true);
SynchronizePropertiesWithUser();
using (var stream = _filesystem.Open(_fileName,
FileMode.Open,
FileAccess.Read,
FileShare.ReadWrite))
{
using (var reader = new StreamReaderEx(stream, _encoding))
{
// We change the error flag explicitly AFTER opening
// the stream because that operation might throw if we're
// not allowed to access the file (in which case a different
// error must be set).
_localProperties.SetValue(Core.Properties.EmptyReason, null);
if (stream.Length >= _lastStreamPosition)
{
stream.Position = _lastStreamPosition;
}
else
{
OnReset(stream, out _numberOfLinesRead, out _lastStreamPosition);
}
int numProcessed = 0;
string currentLine;
while ((currentLine = reader.ReadLine()) != null)
{
token.ThrowIfCancellationRequested();
bool lastLineHadNewline = _lastLineHadNewline;
var trimmedLine = currentLine.TrimNewlineEnd(out _lastLineHadNewline);
var entryCount = _entries.Count;
if (entryCount > 0 && !lastLineHadNewline)
{
// We need to remove the last line and create a new line
// that consists of the entire content.
RemoveLast();
trimmedLine = _untrimmedLastLine + trimmedLine;
_untrimmedLastLine = _untrimmedLastLine + currentLine;
}
else
{
_untrimmedLastLine = currentLine;
++_numberOfLinesRead;
read = true;
}
Add(trimmedLine,
_numberOfLinesRead);
if (++numProcessed % 1000 == 0)
{
// Here's the deal: Since we're processing the file in chunks, we advance the underlying
// stream faster than we're actually consuming lines. This means that it's quite likely
// that at the end of the file, we have moved the stream to the end, but have not quite
// yet processed the underlying buffer from StreamReaderEx. The percentage processed
// should be accurate enough so that if it is at 100%, then no more log entries are added.
// We can only guarantee that when we have processed all lines and therefore we reserve
// setting the percentage to 100% ONLY when we can read no more lines
// (See the SetEndOfSourceReached() call below, outside the loop).
UpdatePercentageProcessed(stream.Position, fileSize, allow100Percent: false);
SynchronizePropertiesWithUser();
}
}
_lastStreamPosition = stream.Position;
_localProperties.SetValue(TextProperties.LineCount, _entries.Count);
_localProperties.SetValue(Core.Properties.LogEntryCount, _entries.Count);
}
}
Listeners.OnRead(_numberOfLinesRead);
SetEndOfSourceReached();
}
}
catch (FileNotFoundException e)
{
SetError(_sourceDoesNotExist);
Log.Debug(e);
}
catch (DirectoryNotFoundException e)
{
SetError(_sourceDoesNotExist);
Log.Debug(e);
}
catch (OperationCanceledException e)
{
Log.Debug(e);
}
catch (UnauthorizedAccessException e)
{
SetError(_sourceCannotBeAccessed);
Log.Debug(e);
}
catch (IOException e)
{
SetError(_sourceCannotBeAccessed);
Log.Debug(e);
}
catch (Exception e)
{
Log.Debug(e);
}
if (read)
{
return(TimeSpan.Zero);
}
return(TimeSpan.FromMilliseconds(100));
}
