private void LoadCache(long vcn)
{
long cuStart = CompressionStart(vcn);
if (_cacheBufferVcn != cuStart)
{
if (_rawStream.AreAllClustersStored(cuStart, _attr.CompressionUnitSize))
{
// Uncompressed data - read straight into cache buffer
_rawStream.ReadClusters(cuStart, _attr.CompressionUnitSize, _cacheBuffer, 0);
}
else if (_rawStream.IsClusterStored(cuStart))
{
// Compressed data - read via IO buffer
_rawStream.ReadClusters(cuStart, _attr.CompressionUnitSize, _ioBuffer, 0);
int expected =
(int)
Math.Min(_attr.Length - vcn * _bytesPerCluster, _attr.CompressionUnitSize * _bytesPerCluster);
int decomp = _context.Options.Compressor.Decompress(_ioBuffer, 0, _ioBuffer.Length, _cacheBuffer, 0);
if (decomp < expected)
{
throw new IOException("Decompression returned too little data");
}
}
else
{
// Sparse, wipe cache buffer directly
Array.Clear(_cacheBuffer, 0, _cacheBuffer.Length);
}
_cacheBufferVcn = cuStart;
}
}
public override void ReadClusters(long startVcn, int count, byte[] buffer, int offset)
{
_rawStream.ReadClusters(startVcn, count, buffer, offset);
}