public override int Read(byte[] buffer, int offset, int count)
{
if (_position >= _length)
{
return(0);
}
int totalRead = 0;
while (totalRead < count && _position < _length)
{
// If current region is outside the area of interest, clean it up
if (_currentExtent != null && (_position < _currentExtent.Start || _position >= _currentExtent.Start + _currentExtent.Length))
{
_currentExtent.DisposeReadState();
_currentExtent = null;
}
// If we need to find a new region, look for it
if (_currentExtent == null)
{
using (SearchExtent searchExtent = new SearchExtent(_position))
{
int idx = _extents.BinarySearch(searchExtent, new ExtentRangeComparer());
if (idx >= 0)
{
BuilderExtent extent = _extents[idx];
extent.PrepareForRead();
_currentExtent = extent;
}
}
}
int numRead = 0;
// If the block is outside any known extent, defer to base stream.
if (_currentExtent == null)
{
_baseStream.Position = _position;
BuilderExtent nextExtent = FindNext(_position);
if (nextExtent != null)
{
numRead = _baseStream.Read(buffer, offset + totalRead, (int)Math.Min(count - totalRead, nextExtent.Start - _position));
}
else
{
numRead = _baseStream.Read(buffer, offset + totalRead, count - totalRead);
}
}
else
{
numRead = _currentExtent.Read(_position, buffer, offset + totalRead, count - totalRead);
}
_position += numRead;
totalRead += numRead;
}
return(totalRead);
}
protected override void Dispose(bool disposing)
{
try
{
if (disposing)
{
if (_currentExtent != null)
{
_currentExtent.DisposeReadState();
_currentExtent = null;
}
if (_baseStream != null)
{
_baseStream.Dispose();
_baseStream = null;
}
}
}
finally
{
base.Dispose(disposing);
}
}