private Metablock ReadMetaBlock(long pos)
{
Metablock block = _metablockCache.GetBlock(pos);
if (block.Available >= 0)
{
return(block);
}
Stream stream = _context.RawStream;
stream.Position = pos;
byte[] buffer = StreamUtilities.ReadFully(stream, 2);
int readLen = EndianUtilities.ToUInt16LittleEndian(buffer, 0);
bool isCompressed = (readLen & 0x8000) == 0;
readLen &= 0x7FFF;
if (readLen == 0)
{
readLen = 0x8000;
}
block.NextBlockStart = pos + readLen + 2;
if (isCompressed)
{
if (_ioBuffer == null || readLen > _ioBuffer.Length)
{
_ioBuffer = new byte[readLen];
}
if (StreamUtilities.ReadFully(stream, _ioBuffer, 0, readLen) != readLen)
{
throw new IOException("Truncated stream reading compressed metadata");
}
using (
ZlibStream zlibStream = new ZlibStream(new MemoryStream(_ioBuffer, 0, readLen, false),
CompressionMode.Decompress, true))
{
block.Available = StreamUtilities.ReadFully(zlibStream, block.Data, 0, MetadataBufferSize);
}
}
else
{
block.Available = StreamUtilities.ReadFully(stream, block.Data, 0, readLen);
}
return(block);
}
public string ReadString(int len)
{
Metablock block = _context.ReadMetaBlock(_start + _currentBlockStart);
if (block.Available - _currentOffset < len)
{
byte[] buffer = new byte[len];
Read(buffer, 0, len);
return(Utilities.BytesToString(buffer, 0, len));
}
string result = Utilities.BytesToString(block.Data, _currentOffset, len);
_currentOffset += len;
return(result);
}
public short ReadShort()
{
Metablock block = _context.ReadMetaBlock(_start + _currentBlockStart);
if (block.Available - _currentOffset < 2)
{
byte[] buffer = new byte[2];
Read(buffer, 0, 2);
return(Utilities.ToInt16LittleEndian(buffer, 0));
}
short result = Utilities.ToInt16LittleEndian(block.Data, _currentOffset);
_currentOffset += 2;
return(result);
}
public int ReadInt()
{
Metablock block = _context.ReadMetaBlock(_start + _currentBlockStart);
if (block.Available - _currentOffset < 4)
{
byte[] buffer = new byte[4];
Read(buffer, 0, 4);
return(Utilities.ToInt32LittleEndian(buffer, 0));
}
int result = Utilities.ToInt32LittleEndian(block.Data, _currentOffset);
_currentOffset += 4;
return(result);
}
public void Skip(int count)
{
Metablock block = _context.ReadMetaBlock(_start + _currentBlockStart);
int totalSkipped = 0;
while (totalSkipped < count)
{
if (_currentOffset >= block.Available)
{
int oldAvailable = block.Available;
block = _context.ReadMetaBlock(block.NextBlockStart);
_currentBlockStart = block.Position - _start;
_currentOffset -= oldAvailable;
}
int toSkip = Math.Min(count - totalSkipped, block.Available - _currentOffset);
totalSkipped += toSkip;
_currentOffset += toSkip;
}
}
public int Read(byte[] buffer, int offset, int count)
{
Metablock block = _context.ReadMetaBlock(_start + _currentBlockStart);
int totalRead = 0;
while (totalRead < count)
{
if (_currentOffset >= block.Available)
{
int oldAvailable = block.Available;
block = _context.ReadMetaBlock(block.NextBlockStart);
_currentBlockStart = block.Position - _start;
_currentOffset -= oldAvailable;
}
int toRead = Math.Min(count - totalRead, block.Available - _currentOffset);
Array.Copy(block.Data, _currentOffset, buffer, offset + totalRead, toRead);
totalRead += toRead;
_currentOffset += toRead;
}
return(totalRead);
}
