public int Read(int dataId, byte[] buffer, int offset, int length)
{
if (dataId < 0 || dataId >= 16384)
{
throw new ArgumentException("dataId out of range");
}
try {
int dataPointer = dataId;
int pos = dataPointer * 6;
int dataIdPos = pagedAccess.ReadInt32(pos);
int dataIdLength = ((int)pagedAccess.ReadInt16(pos + 4)) & 0x0FFFF;
if (dataIdPos < 0)
{
dataPointer = -(dataIdPos + 1);
pos = dataPointer * 6;
dataIdPos = pagedAccess.ReadInt32(pos);
dataIdLength = ((int)pagedAccess.ReadInt16(pos + 4)) & 0x0FFFF;
}
length = Math.Min(length, dataIdLength);
// Read the encoded form into a byte[] array,
content.Seek(dataIdPos, SeekOrigin.Begin);
return(content.Read(buffer, offset, length));
} catch (IOException e) {
// We wrap this IOException around a BlockReadException. This can only
// indicate a corrupt compressed block file or access to a dataId that
// is out of range of the nodes stored in this file.
throw new BlockReadException("IOError reading data from block file", e);
}
}
public void Write(int dataId, byte[] buffer, int offset, int count)
{
// Arg checks
if (count < 0 || count >= 65536)
{
throw new ArgumentException("count < 0 || count > 65535");
}
if (count + offset > buffer.Length)
{
throw new ArgumentException();
}
if (offset < 0)
{
throw new ArgumentException();
}
if (dataId < 0 || dataId >= 16384)
{
throw new ArgumentException("dataId out of range");
}
byte[] tmpArea = new byte[6];
// Seek to the position of this data id in the table,
int pos = dataId * 6;
int dataIdPos = pagedAccess.ReadInt32(pos);
int dataIdLength = (pagedAccess.ReadInt16(pos + 4)) & 0x0FFFF;
// These values should be 0, if not we've already written data here,
if (dataIdPos != 0 || dataIdLength != 0)
{
throw new ApplicationException("data_id previously written");
}
// Write the content to the end of the file,
content.Seek(length, SeekOrigin.Begin);
content.Write(buffer, offset, count);
pagedAccess.InvalidateSection(length, count);
// Write the table entry,
ByteBuffer.WriteInt4(length, tmpArea, 0);
ByteBuffer.WriteInt2((short)count, tmpArea, 4);
content.Seek(pos, SeekOrigin.Begin);
content.Write(tmpArea, 0, 6);
pagedAccess.InvalidateSection(pos, 6);
// Set the new content length
length = length + count;
}