示例#1
0
        /// <summary>
        /// See <see cref="IByteProvider.ApplyChanges" /> for more information.
        /// </summary>
        public void ApplyChanges()
        {
            if (_readOnly)
            {
                throw new OperationCanceledException("File is in read-only mode");
            }

            // This method is implemented to efficiently save the changes to the same file stream opened for reading.
            // Saving to a separate file would be a much simpler implementation.

            // Firstly, extend the file length (if necessary) to ensure that there is enough disk space.
            if (_totalLength > _stream.Length)
            {
                _stream.SetLength(_totalLength);
            }

            // Secondly, shift around any file sections that have moved.
            long dataOffset = 0;

            for (DataBlock block = _dataMap.FirstBlock; block != null; block = block.NextBlock)
            {
                FileDataBlock fileBlock = block as FileDataBlock;
                if (fileBlock != null && fileBlock.FileOffset != dataOffset)
                {
                    MoveFileBlock(fileBlock, dataOffset);
                }
                dataOffset += block.Length;
            }

            // Next, write in-memory changes.
            dataOffset = 0;
            for (DataBlock block = _dataMap.FirstBlock; block != null; block = block.NextBlock)
            {
                MemoryDataBlock memoryBlock = block as MemoryDataBlock;
                if (memoryBlock != null)
                {
                    _stream.Position = dataOffset;
                    for (int memoryOffset = 0; memoryOffset < memoryBlock.Length; memoryOffset += COPY_BLOCK_SIZE)
                    {
                        _stream.Write(memoryBlock.Data, memoryOffset, (int)Math.Min(COPY_BLOCK_SIZE, memoryBlock.Length - memoryOffset));
                    }
                }
                dataOffset += block.Length;
            }

            // Finally, if the file has shortened, truncate the stream.
            _stream.SetLength(_totalLength);
            ReInitialize();
        }
示例#2
0
        /// <summary>
        /// See <see cref="IByteProvider.ReadByte" /> for more information.
        /// </summary>
        public byte ReadByte(long index)
        {
            long          blockOffset;
            DataBlock     block     = GetDataBlock(index, out blockOffset);
            FileDataBlock fileBlock = block as FileDataBlock;

            if (fileBlock != null)
            {
                return(ReadByteFromFile(fileBlock.FileOffset + index - blockOffset));
            }
            else
            {
                MemoryDataBlock memoryBlock = (MemoryDataBlock)block;
                return(memoryBlock.Data[index - blockOffset]);
            }
        }
示例#3
0
        /// <summary>
        /// See <see cref="IByteProvider.InsertBytes" /> for more information.
        /// </summary>
        public void InsertBytes(long index, byte[] bs)
        {
            try
            {
                // Find the block affected.
                long      blockOffset;
                DataBlock block = GetDataBlock(index, out blockOffset);

                // If the insertion point is in a memory block, just insert it.
                MemoryDataBlock memoryBlock = block as MemoryDataBlock;
                if (memoryBlock != null)
                {
                    memoryBlock.InsertBytes(index - blockOffset, bs);
                    return;
                }

                FileDataBlock fileBlock = (FileDataBlock)block;

                // If the insertion point is at the start of a file block, and the previous block is a memory block, append it to that block.
                if (blockOffset == index && block.PreviousBlock != null)
                {
                    MemoryDataBlock previousMemoryBlock = block.PreviousBlock as MemoryDataBlock;
                    if (previousMemoryBlock != null)
                    {
                        previousMemoryBlock.InsertBytes(previousMemoryBlock.Length, bs);
                        return;
                    }
                }

                // Split the block into a prefix and a suffix and place a memory block in-between.
                FileDataBlock prefixBlock = null;
                if (index > blockOffset)
                {
                    prefixBlock = new FileDataBlock(fileBlock.FileOffset, index - blockOffset);
                }

                FileDataBlock suffixBlock = null;
                if (index < blockOffset + fileBlock.Length)
                {
                    suffixBlock = new FileDataBlock(
                        fileBlock.FileOffset + index - blockOffset,
                        fileBlock.Length - (index - blockOffset));
                }

                block = _dataMap.Replace(block, new MemoryDataBlock(bs));

                if (prefixBlock != null)
                {
                    _dataMap.AddBefore(block, prefixBlock);
                }

                if (suffixBlock != null)
                {
                    _dataMap.AddAfter(block, suffixBlock);
                }
            }
            finally
            {
                _totalLength += bs.Length;
                OnLengthChanged(EventArgs.Empty);
                OnChanged(EventArgs.Empty);
            }
        }
示例#4
0
        /// <summary>
        /// See <see cref="IByteProvider.WriteByte" /> for more information.
        /// </summary>
        public void WriteByte(long index, byte value)
        {
            try
            {
                // Find the block affected.
                long      blockOffset;
                DataBlock block = GetDataBlock(index, out blockOffset);

                // If the byte is already in a memory block, modify it.
                MemoryDataBlock memoryBlock = block as MemoryDataBlock;
                if (memoryBlock != null)
                {
                    memoryBlock.Data[index - blockOffset] = value;
                    return;
                }

                FileDataBlock fileBlock = (FileDataBlock)block;

                // If the byte changing is the first byte in the block and the previous block is a memory block, extend that.
                if (blockOffset == index && block.PreviousBlock != null)
                {
                    MemoryDataBlock previousMemoryBlock = block.PreviousBlock as MemoryDataBlock;
                    if (previousMemoryBlock != null)
                    {
                        previousMemoryBlock.AddByteToEnd(value);
                        fileBlock.RemoveBytesFromStart(1);
                        if (fileBlock.Length == 0)
                        {
                            _dataMap.Remove(fileBlock);
                        }
                        return;
                    }
                }

                // If the byte changing is the last byte in the block and the next block is a memory block, extend that.
                if (blockOffset + fileBlock.Length - 1 == index && block.NextBlock != null)
                {
                    MemoryDataBlock nextMemoryBlock = block.NextBlock as MemoryDataBlock;
                    if (nextMemoryBlock != null)
                    {
                        nextMemoryBlock.AddByteToStart(value);
                        fileBlock.RemoveBytesFromEnd(1);
                        if (fileBlock.Length == 0)
                        {
                            _dataMap.Remove(fileBlock);
                        }
                        return;
                    }
                }

                // Split the block into a prefix and a suffix and place a memory block in-between.
                FileDataBlock prefixBlock = null;
                if (index > blockOffset)
                {
                    prefixBlock = new FileDataBlock(fileBlock.FileOffset, index - blockOffset);
                }

                FileDataBlock suffixBlock = null;
                if (index < blockOffset + fileBlock.Length - 1)
                {
                    suffixBlock = new FileDataBlock(
                        fileBlock.FileOffset + index - blockOffset + 1,
                        fileBlock.Length - (index - blockOffset + 1));
                }

                block = _dataMap.Replace(block, new MemoryDataBlock(value));

                if (prefixBlock != null)
                {
                    _dataMap.AddBefore(block, prefixBlock);
                }

                if (suffixBlock != null)
                {
                    _dataMap.AddAfter(block, suffixBlock);
                }
            }
            finally
            {
                OnChanged(EventArgs.Empty);
            }
        }