public void Decompress(Stream source, Stream sink)
{
if (source == null)
throw new ArgumentNullException("source");
if (sink == null)
throw new ArgumentNullException("sink");
Invariant.Assert(source.CanRead);
Invariant.Assert(sink.CanWrite, "Logic Error - Cannot decompress into a read-only stream");
// remember this for later
long storedPosition = -1;
try
{
if (source.CanSeek)
{
storedPosition = source.Position;
source.Position = 0;
}
if (sink.CanSeek)
sink.Position = 0;
// zlib state
UnsafeNativeMethods.ZStream zStream = new UnsafeNativeMethods.ZStream();
// initialize the zlib library
UnsafeNativeMethods.ZLib.ErrorCode retVal = 0;
retVal = UnsafeNativeMethods.ZLib.ums_inflate_init(ref zStream,
UnsafeNativeMethods.ZLib.ZLibVersion, Marshal.SizeOf(zStream));
ThrowIfZLibError(retVal);
byte[] sourceBuf = null; // source buffer
byte[] sinkBuf = null; // destination buffer - where to write data
GCHandle gcSourceBuf = new GCHandle(); // Preallocate these so we can safely access them
GCHandle gcSinkBuf = new GCHandle(); // in the next finally block.
try
{
// read all available data
// each block is preceded by a header that is 3 ulongs
int uncompressedSize, compressedSize;
long destStreamLength = 0; // keep track of decompressed size
while (ReadBlockHeader(source, out uncompressedSize, out compressedSize))
{
// ensure we have space
AllocOrRealloc(compressedSize, ref sourceBuf, ref gcSourceBuf);
AllocOrRealloc(uncompressedSize, ref sinkBuf, ref gcSinkBuf);
// read the data into the sourceBuf
int bytesRead = PackagingUtilities.ReliableRead(source, sourceBuf, 0, compressedSize);
if (bytesRead > 0)
{
if (compressedSize != bytesRead)
throw new FileFormatException(SR.Get(SRID.CorruptStream));
// prepare structure
// The buffer pointers must be reset for every call
// because ums_inflate modifies them
zStream.pInBuf = gcSourceBuf.AddrOfPinnedObject();
zStream.pOutBuf = gcSinkBuf.AddrOfPinnedObject();
zStream.cbIn = (uint)bytesRead; // this is number of bytes available for decompression at pInBuf and is updated by ums_deflate call
zStream.cbOut = (uint)sinkBuf.Length; // this is the number of bytes free in pOutBuf and is updated by ums_deflate call
// InvokeZLib does the actual interop. It updates zStream, and sinkBuf (sourceBuf passed by ref to avoid copying)
// and leaves the decompressed data in sinkBuf.
// int decompressedSize = InvokeZLib(bytesRead, ref zStream, ref sourceBuf, ref sinkBuf, pSource, pSink, false);
retVal = UnsafeNativeMethods.ZLib.ums_inflate(ref zStream,
(int)UnsafeNativeMethods.ZLib.FlushCodes.SyncFlush);
ThrowIfZLibError(retVal);
checked
{
int decompressedSize = sinkBuf.Length - (int)zStream.cbOut;
// verify that data matches header
if (decompressedSize != uncompressedSize)
throw new FileFormatException(SR.Get(SRID.CorruptStream));
destStreamLength += decompressedSize;
// write to the base stream
sink.Write(sinkBuf, 0, decompressedSize);
}
}
else
{
// block header but no block data
if (compressedSize != 0)
throw new FileFormatException(SR.Get(SRID.CorruptStream));
}
}
// make sure we truncate if the destination stream was longer than this current decompress
if (sink.CanSeek)
sink.SetLength(destStreamLength);
}
finally
{
if (gcSourceBuf.IsAllocated)
gcSourceBuf.Free();
if (gcSinkBuf.IsAllocated)
gcSinkBuf.Free();
}
}
finally
{
// seek to the current logical position before returning
if (source.CanSeek)
source.Position = storedPosition;
}
}
public void Compress(Stream source, Stream sink)
{
if (source == null)
throw new ArgumentNullException("source");
if (sink == null)
throw new ArgumentNullException("sink");
Invariant.Assert(source.CanRead);
Invariant.Assert(sink.CanWrite, "Logic Error - Cannot compress into a read-only stream");
// remember this for later if possible
long storedPosition = -1; // default to illegal value to catch any logic errors
try
{
int sourceBufferSize; // don't allocate 4k for really tiny source streams
if (source.CanSeek)
{
storedPosition = source.Position;
source.Position = 0;
// Casting result to int is safe because _defaultBlockSize is very small and the result
// of Math.Min(x, _defaultBlockSize) must be no larger than _defaultBlockSize.
sourceBufferSize = (int)(Math.Min(source.Length, (long)_defaultBlockSize));
}
else
sourceBufferSize = _defaultBlockSize; // can't call Length so fallback to default
if (sink.CanSeek)
sink.Position = 0;
// zlib state
UnsafeNativeMethods.ZStream zStream = new UnsafeNativeMethods.ZStream();
// initialize the zlib library
UnsafeNativeMethods.ZLib.ErrorCode retVal = UnsafeNativeMethods.ZLib.ums_deflate_init(ref zStream, _compressionLevel,
UnsafeNativeMethods.ZLib.ZLibVersion, Marshal.SizeOf(zStream));
ThrowIfZLibError(retVal);
// where to write data - can actually grow if data is uncompressible
long destStreamLength = 0;
byte[] sourceBuf = null; // source buffer
byte[] sinkBuf = null; // destination buffer
GCHandle gcSourceBuf = new GCHandle();
GCHandle gcSinkBuf = new GCHandle();
try
{
// allocate managed buffers
AllocOrRealloc(sourceBufferSize, ref sourceBuf, ref gcSourceBuf);
AllocOrRealloc(_defaultBlockSize + (_defaultBlockSize >> 1), ref sinkBuf, ref gcSinkBuf);
// while (more data is available)
// - read into the sourceBuf
// - compress into the sinkBuf
// - emit the header
// - write out to the _baseStream
// Suppress 6518 Local IDisposable object not disposed:
// Reason: The stream is not owned by us, therefore we cannot
// close the BinaryWriter as it will Close the stream underneath.
#pragma warning disable 6518
BinaryWriter writer = new BinaryWriter(sink);
int bytesRead;
while ((bytesRead = PackagingUtilities.ReliableRead(source, sourceBuf, 0, sourceBuf.Length)) > 0)
{
Invariant.Assert(bytesRead <= sourceBufferSize);
// prepare structure
// these pointers must be re-assigned for each loop because
// ums_deflate modifies them
zStream.pInBuf = gcSourceBuf.AddrOfPinnedObject();
zStream.pOutBuf = gcSinkBuf.AddrOfPinnedObject();
zStream.cbIn = (uint)bytesRead; // this is number of bytes available for compression at pInBuf and is updated by ums_deflate call
zStream.cbOut = (uint)sinkBuf.Length; // this is the number of bytes free in pOutBuf and is updated by ums_deflate call
// cast is safe because SyncFlush is a constant
retVal = UnsafeNativeMethods.ZLib.ums_deflate(ref zStream,
(int)UnsafeNativeMethods.ZLib.FlushCodes.SyncFlush);
ThrowIfZLibError(retVal);
checked
{
int compressedSize = sinkBuf.Length - (int)zStream.cbOut;
Invariant.Assert(compressedSize > 0, "compressing non-zero bytes creates a non-empty block");
// This should never happen because our destination buffer
// is twice as large as our source buffer
Invariant.Assert(zStream.cbIn == 0, "Expecting all data to be compressed!");
// write the header
writer.Write(_blockHeaderToken); // token
writer.Write((UInt32)bytesRead);
writer.Write((UInt32)compressedSize);
destStreamLength += _headerBuf.Length;
// write to the base stream
sink.Write(sinkBuf, 0, compressedSize);
destStreamLength += compressedSize;
}
}
// post-compression
// truncate if necessary
if (sink.CanSeek)
sink.SetLength(destStreamLength);
}
finally
{
if (gcSourceBuf.IsAllocated)
gcSourceBuf.Free();
if (gcSinkBuf.IsAllocated)
gcSinkBuf.Free();
}
#pragma warning restore 6518
}
finally
{
// seek to the current logical position before returning
if (sink.CanSeek)
source.Position = storedPosition;
}
}
