/// <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();
}
/// <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]);
}
}
/// <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);
}
}
/// <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);
}
}