public Stream Read(ref BlockRef block, bool headerOnly, FGet fget)
{
bool retry;
byte[] bytes;
int readBytes, headerSize, length;
do
{
retry = false;
long position = _sectionPosition + (BlockSize * block.Offset);
bytes = new byte[headerOnly ? BlockHeaderSize : block.ActualBlocks * BlockSize];
readBytes = fget(position, bytes, 0, bytes.Length);
if (readBytes < BlockHeaderSize)
{
throw new InvalidDataException();
}
headerSize = bytes[OffsetOfHeaderSize];
length = (int)GetUInt32(bytes, OffsetOfLength) & 0x00FFFFFF;
block.ActualBlocks = (int)GetUInt32(bytes, OffsetOfBlockCount);
uint blockId = GetUInt32(bytes, OffsetOfBlockId);
if (headerSize < BlockHeaderSize || blockId != block.Identity ||
((block.Count < 16 && block.ActualBlocks != block.Count) ||
(block.Count == 16 && block.ActualBlocks < 16)))
{
throw new InvalidDataException();
}
if (block.ActualBlocks != Math.Max(1, (length + headerSize + BlockSize - 1) / BlockSize))
{
throw new InvalidDataException();
}
if (headerOnly)
{
return(null);
}
if (readBytes < length + headerSize)
{
retry = bytes.Length != block.ActualBlocks * BlockSize;
}
} while (retry);
if (readBytes < length + headerSize)
{
throw new InvalidDataException();
}
Crc32 crc = new Crc32();
crc.Add(bytes, headerSize, length);
if ((uint)crc.Value != GetUInt32(bytes, OffsetOfCrc32))
{
throw new InvalidDataException();
}
return(new MemoryStream(bytes, headerSize, length, false, false));
}