Method ReadBytes

stfschk/StfsFileSystem.cs:754–815

(IntPtr buffer, ulong fileOffset, uint length)

            }

            public uint ReadBytes(IntPtr buffer, ulong fileOffset, uint length)
            {
                if (fileOffset >= Size)
                    return 0;

                if (fileOffset + length >= Size)
                    length = (uint)(Size - fileOffset);

                if (FakeData != null)
                {
                    byte[] bytes2 = new byte[length];
                    int read = 0;
                    lock (FakeData)
                    {
                        FakeData.Seek((long)fileOffset, SeekOrigin.Begin);
                        read = FakeData.Read(bytes2, 0, bytes2.Length);
                    }
                    Marshal.Copy(bytes2, 0, buffer, read);
                    return (uint)read;
                }

                // Lock so that two threads can't try updating chain at once...
                lock (this)
                    if (BlockChain == null)
                        BlockChain = FileSystem.StfsGetDataBlockChain(DirEntry.FirstBlockNumber);

                uint chainNum = (uint)(fileOffset / kSectorSize);
                uint blockOffset = (uint)(fileOffset % kSectorSize);

                uint blockRemaining = kSectorSize - blockOffset;
                uint lengthRemaining = length;
                uint transferred = 0;

                byte[] bytes = new byte[kSectorSize];
                while (lengthRemaining > 0)
                {
                    var blockNum = BlockChain[chainNum];

                    uint toRead = blockRemaining;
                    if (toRead > lengthRemaining)
                        toRead = lengthRemaining;

                    int read = 0;
                    lock (FileSystem.StreamLock)
                    {
                        FileSystem.Stream.Seek((long)FileSystem.StfsDataBlockToOffset(blockNum) + blockOffset, SeekOrigin.Begin);
                        read = FileSystem.Stream.Read(bytes, 0, (int)toRead);
                    }

                    Marshal.Copy(bytes, 0, buffer, read);
                    transferred += (uint)read;

                    if (blockOffset + read >= kSectorSize)
                        chainNum++;

                    buffer += read;
                    blockRemaining = kSectorSize;
                    blockOffset = 0;