private bool CanCollapseWithPreviousBlock(MemoryStreamBlock memStreamBlock,
long offset,
long length)
{
// There was an explicit request by the client not to merge near- by blocks
if (!_autoCloseSmallBlockGaps || memStreamBlock == null)
{
return(false);
}
checked
{
long gap = offset - (memStreamBlock.Offset + memStreamBlock.Stream.Length);
Debug.Assert(gap >= 0);
// if gap between them is smaller then a fix overhead of an extra block
// and these are not too big to not fit in the MemoryStream Int32.MaxValue
if (gap <= _fixBlockInMemoryOverhead &&
gap + length + memStreamBlock.Stream.Length <= Int32.MaxValue)
{
return(true);
}
}
return(false);
}
private void SwitchModeIfNecessary()
{
if (_isolatedStorageMode)
{
Debug.Assert(_memoryStreamList.Count == 0); // it must be empty in isolated storage mode
// if we are in isolated storage mode we need to check the Low Water Mark crossing
if (_isolatedStorageStream.Length < _lowWaterMark)
{
if (_isolatedStorageStream.Length > 0)
{
//build memory stream
MemoryStreamBlock newMemStreamBlock = new MemoryStreamBlock
(_trackingMemoryStreamFactory.Create((int)_isolatedStorageStream.Length),
0);
//copy data from iso storage to memory stream
_isolatedStorageStream.Seek(0, SeekOrigin.Begin);
newMemStreamBlock.Stream.Seek(0, SeekOrigin.Begin);
PackagingUtilities.CopyStream(_isolatedStorageStream, newMemStreamBlock.Stream,
Int64.MaxValue /*bytes to copy*/,
0x80000 /*512K buffer size */);
Debug.Assert(newMemStreamBlock.Stream.Length > 0);
_memoryStreamList.Add(newMemStreamBlock);
}
//switch mode
_isolatedStorageMode = false;
// release isolated storage disk space by setting its length to 0
// This way we don't have to re-open the isolated storage again if the memory consumption
// goes above the High Water Mark
_isolatedStorageStream.SetLength(0);
_isolatedStorageStream.Flush();
}
}
else
{
// if we are in Memory Stream mode we need to check the High Water Mark crossing
if (_trackingMemoryStreamFactory.CurrentMemoryConsumption > _highWaterMark)
{
//copy data to isolated storage
EnsureIsolatedStoreStream();
CopyMemoryBlocksToStream(_isolatedStorageStream);
//switch mode
_isolatedStorageMode = true;
//release memory stream resources
foreach (MemoryStreamBlock memStreamBlock in _memoryStreamList)
{
// this will report the appropriate Memory usage back to the ITrackingMemoryStreamFactory
memStreamBlock.Stream.Close();
}
_memoryStreamList.Clear();
}
}
}
private MemoryStreamBlock GetSearchBlockForOffset(long offset)
{
if (_searchBlock == null)
{
_searchBlock = new MemoryStreamBlock(null, offset);
}
else
{
_searchBlock.Offset = offset;
}
return(_searchBlock);
}
private MemoryStreamBlock ConstructMemoryStreamFromWriteRequest(
byte[] buffer, // data buffer to be used for the new Memory Stream Block
long writeRequestOffset,
int writeRequestSize,
int bufferOffset)
{
Debug.Assert(!_isolatedStorageMode);
MemoryStreamBlock newMemStreamBlock = new MemoryStreamBlock
(_trackingMemoryStreamFactory.Create(writeRequestSize),
writeRequestOffset);
newMemStreamBlock.Stream.Seek(0, SeekOrigin.Begin);
newMemStreamBlock.Stream.Write(buffer, bufferOffset, writeRequestSize);
return(newMemStreamBlock);
}
public override void SetLength(long newLength)
{
CheckDisposed();
if (newLength < 0)
{
throw new ArgumentOutOfRangeException("newLength");
}
#if DEBUG
DebugAssertConsistentArrayStructure();
#endif
if (_currentStreamLength != newLength)
{
if (_isolatedStorageMode)
{
lock (PackagingUtilities.IsolatedStorageFileLock)
{
_isolatedStorageStream.SetLength(newLength);
}
}
else
{
// if length become smaller , we might be able to close some of memoryStreams that we keep around
if (_currentStreamLength > newLength)
{
int removeIndex = _memoryStreamList.BinarySearch(GetSearchBlockForOffset(newLength));
// the new end of the stream does not fall into any existing blocks
if (removeIndex < 0)
{
// ~removeIndex represents the place at which we would insert the new block for write
removeIndex = ~removeIndex;
}
else
{
// we need to truncate the MemoryStream
MemoryStreamBlock memStreamBlock = _memoryStreamList[removeIndex];
checked
{
long temp = newLength - memStreamBlock.Offset;
if (temp > 0)
{
memStreamBlock.Stream.SetLength(temp);
++removeIndex;
}
// else fall through and remove below
}
}
for (int i = removeIndex; i < _memoryStreamList.Count; ++i)
{
_memoryStreamList[i].Stream.Close(); // we need to carefully close the memoryStreams so they properly report the memory usage
}
_memoryStreamList.RemoveRange(removeIndex, _memoryStreamList.Count - removeIndex);
}
}
_currentStreamLength = newLength;
if (_currentStreamPosition > _currentStreamLength)
{
_currentStreamPosition = _currentStreamLength;
}
}
// this can potentially affect memory consumption
SwitchModeIfNecessary();
#if DEBUG
DebugAssertConsistentArrayStructure();
#endif
}
private void WriteAndCollapseBlocks(byte[] buffer,
int offset,
int count)
{
int index = _memoryStreamList.BinarySearch(GetSearchBlockForOffset(_currentStreamPosition));
bool writeDone = false;
MemoryStreamBlock memStreamBlock = null;
MemoryStreamBlock prevMemStreamBlock = null;
checked
{
if (index < 0) // the head of new write block does not overlap with any existing blocks
{
// ~startIndex represents the place at which we would insert the new block for write
index = ~index;
if (index != 0) // Get the previous block of the new write block
{
prevMemStreamBlock = _memoryStreamList[index - 1];
}
// If the write request is close enough to the previous block and if the collapsing is allowed
if (CanCollapseWithPreviousBlock(prevMemStreamBlock, _currentStreamPosition, (long)count))
{
// write out any intervening zero's
prevMemStreamBlock.Stream.Seek(0, SeekOrigin.End);
SkipWrite(prevMemStreamBlock.Stream, prevMemStreamBlock.EndOffset, _currentStreamPosition);
prevMemStreamBlock.Stream.Write(buffer, offset, count);
writeDone = true;
}
}
else
{
prevMemStreamBlock = _memoryStreamList[index];
// Write the requested bytes to the existing block if possible
if (prevMemStreamBlock.Stream.Length + count <= Int32.MaxValue) // Make sure there is enough space to append
{
prevMemStreamBlock.Stream.Seek(_currentStreamPosition - prevMemStreamBlock.Offset, SeekOrigin.Begin);
prevMemStreamBlock.Stream.Write(buffer, offset, count);
writeDone = true;
++index;
}
else // Not enough space
{
// There is overlap but we will created a new block for the write request; need to truncate the prev block
prevMemStreamBlock.Stream.SetLength(_currentStreamPosition - prevMemStreamBlock.Offset);
Debug.Assert(prevMemStreamBlock.Stream.Length > 0);
}
}
if (!writeDone) // create a new block for the write request
{
prevMemStreamBlock = ConstructMemoryStreamFromWriteRequest(buffer, _currentStreamPosition, count, offset);
Debug.Assert(prevMemStreamBlock.Stream.Length > 0);
_memoryStreamList.Insert(index, prevMemStreamBlock);
++index;
}
_currentStreamPosition += count; // Update the stream position since the write request is satisfied by this point
int i;
// Close and remove all completely-overlapping blocks
for (i = index; i < _memoryStreamList.Count; ++i)
{
if (_memoryStreamList[i].EndOffset > _currentStreamPosition)
{
break;
}
_memoryStreamList[i].Stream.Close(); // we need to carefully close the memoryStreams so they properly report the memory usage
}
if (i - index > 0)
{
_memoryStreamList.RemoveRange(index, i - index);
}
///////////////////////////////////////////
// Check if the tail of the new write block needs to be collapsed with the following block
///////////////////////////////////////////
long blockOffset = -1;
if (index < _memoryStreamList.Count) // Get the next block of the new write block
{
memStreamBlock = _memoryStreamList[index];
blockOffset = _currentStreamPosition - memStreamBlock.Offset;
}
else
{
memStreamBlock = null; // No next block to check
}
if (blockOffset <= 0) // No overlapping
{
// Check if we should collapse the block
if (memStreamBlock != null &&
(CanCollapseWithPreviousBlock(prevMemStreamBlock, memStreamBlock.Offset, memStreamBlock.Stream.Length)))
{
// remove the following block memStreamBlock
_memoryStreamList.RemoveAt(index);
// write out any intervening zero's
prevMemStreamBlock.Stream.Seek(0, SeekOrigin.End);
SkipWrite(prevMemStreamBlock.Stream, _currentStreamPosition, memStreamBlock.Offset);
prevMemStreamBlock.Stream.Write(memStreamBlock.Stream.GetBuffer(), 0, (int)memStreamBlock.Stream.Length);
}
}
else // Overlapping
{
_memoryStreamList.RemoveAt(index);
// Memory stream length or buffer offset cannot be bigger than Int32.MaxValue
int leftoverSize = (int)(memStreamBlock.Stream.Length - blockOffset);
if (prevMemStreamBlock.Stream.Length + leftoverSize <= Int32.MaxValue)
{
prevMemStreamBlock.Stream.Seek(0, SeekOrigin.End);
prevMemStreamBlock.Stream.Write(memStreamBlock.Stream.GetBuffer(), (int)blockOffset, leftoverSize);
}
else
{
memStreamBlock = ConstructMemoryStreamFromWriteRequest(memStreamBlock.Stream.GetBuffer(),
_currentStreamPosition,
leftoverSize,
(int)blockOffset);
Debug.Assert(memStreamBlock.Stream.Length > 0);
_memoryStreamList.Insert(index, memStreamBlock);
}
}
}
}
override public int Read(byte[] buffer, int offset, int count)
{
CheckDisposed();
PackagingUtilities.VerifyStreamReadArgs(this, buffer, offset, count);
Debug.Assert(_currentStreamPosition >= 0);
if (count == 0)
{
return(0);
}
if (_currentStreamLength <= _currentStreamPosition)
{
// we are past the end of the stream so let's just return 0
return(0);
}
// No need to use checked{} since _currentStreamLength > _currentStreamPosition
int bytesToRead = (int)Math.Min((long)count, _currentStreamLength - _currentStreamPosition);
checked
{
Debug.Assert(bytesToRead > 0);
int bytesRead; // how much data we actually were able to read
if (_isolatedStorageMode)
{
lock (PackagingUtilities.IsolatedStorageFileLock)
{
_isolatedStorageStream.Seek(_currentStreamPosition, SeekOrigin.Begin);
bytesRead = _isolatedStorageStream.Read(buffer, offset, bytesToRead);
}
}
else
{
// let's reset data to 0 first, so that gaps will be filled with 0s
// this is required for consistent behavior between the read calls used by the CRC Calculator
// and the WriteToStream calls used by the Flush/Save routines
Array.Clear(buffer, offset, bytesToRead);
int index = _memoryStreamList.BinarySearch(GetSearchBlockForOffset(_currentStreamPosition));
if (index < 0) // the head of new write block does not overlap with any existing blocks
// ~startIndex represents the insertion position
{
index = ~index;
}
for ( ; index < _memoryStreamList.Count; ++index)
{
MemoryStreamBlock memStreamBlock = _memoryStreamList[index];
long overlapBlockOffset;
long overlapBlockSize;
// let's check for overlap and fill up appropriate data
PackagingUtilities.CalculateOverlap(memStreamBlock.Offset, (int)memStreamBlock.Stream.Length,
_currentStreamPosition, bytesToRead,
out overlapBlockOffset, out overlapBlockSize);
if (overlapBlockSize > 0)
{
// we got an overlap let's copy data over to the target buffer
// _currentStreamPosition is not updated in this foreach loop; it will be updated later
Array.Copy(memStreamBlock.Stream.GetBuffer(), (int)(overlapBlockOffset - memStreamBlock.Offset),
buffer, (int)(offset + overlapBlockOffset - _currentStreamPosition),
(int)overlapBlockSize);
}
else
{
break;
}
}
// for memory stream case we get as much as we asked for
bytesRead = bytesToRead;
}
_currentStreamPosition += bytesRead;
return(bytesRead);
}
}
