AZ::IO::CompressorZLib Class Reference

#include <CompressorZLib.h>

Inherits AZ::IO::Compressor.

Public Member Functions
	AZ_CLASS_ALLOCATOR (CompressorZLib, AZ::SystemAllocator)
	CompressorZLib (unsigned int decompressionCachePerStream=64 *1024, unsigned int dataBufferSize=128 *1024)
AZ::u32	GetTypeId () const override
	Return compressor type id.
bool	ReadHeaderAndData (CompressorStream *stream, AZ::u8 *data, unsigned int dataSize) override
	Called when we open a stream to Read for the first time. Data contains the first. dataSize <= m_maxHeaderSize.
bool	WriteHeaderAndData (CompressorStream *stream) override
	Called when we are about to start writing to a compressed stream.
SizeType	Read (CompressorStream *stream, SizeType byteSize, SizeType offset, void *buffer) override
	Forwarded function from the Device when we from a compressed stream.
SizeType	Write (CompressorStream *stream, SizeType byteSize, const void *data, SizeType offset=SizeType(-1)) override
	Forwarded function from the Device when we write to a compressed stream.
bool	WriteSeekPoint (CompressorStream *stream) override
	Write a seek point.
bool	StartCompressor (CompressorStream *stream, int compressionLevel, SizeType autoSeekDataSize) override
	Set auto seek point even dataSize bytes.
bool	Close (CompressorStream *stream) override
	Called just before we close the stream. All compression data will be flushed and finalized. (You can't add data afterwards).
Public Member Functions inherited from AZ::IO::Compressor
virtual	~Compressor ()
	When we open a stream to check if it's compressed we read the first m_maxHeaderSize bytes.

Static Public Member Functions
static AZ::u32	TypeId ()
	Return compressor type id.

Protected Member Functions
SizeType	FillFromDecompressCache (CompressorZLibData *zlibData, void *&buffer, SizeType &byteSize, SizeType &offset)
	Read as much data as possible and adjust the parameters.
SizeType	FillCompressedBuffer (CompressorStream *stream)
	Read data from stream into the compression buffer.
void	AcquireDataBuffer ()
	Acquire data buffer resource (if not created it will be allocated) and increment m_dataBufferUseCount.
void	ReleaseDataBuffer ()
	Release data buffer resource, if m_dataBufferUseCount == 0 all memory will be freed.

Protected Attributes
CompressorStream *	m_lastReadStream
	Cached last stream we read data into the m_dataBuffer.
SizeType	m_lastReadStreamOffset
	Offset of the last read (in the m_dataBuffer) in the compressed stream.
SizeType	m_lastReadStreamSize
	Size of the data in m_dataBuffer of the last read.
unsigned char *	m_compressedDataBuffer
	Data buffer used to read/write compressed data.
unsigned int	m_compressedDataBufferSize
	Data buffer size (stored so we can lazy allocate m_dataBuffer as we need).
unsigned int	m_compressedDataBufferUseCount
	Data buffer use count.
unsigned int	m_decompressionCachePerStream
	Cache per stream for each compressed stream stream in bytes.

Static Protected Attributes
static const int	m_CompressedDataBufferAlignment = 16

Additional Inherited Members
Public Types inherited from AZ::IO::Compressor
typedef AZ::u64	SizeType
Static Public Attributes inherited from AZ::IO::Compressor
static const int	m_maxHeaderSize = 4096

Detailed Description

ZLib compressor implementation. Note: As of now the CompressorZLib is the only supported compressor. We can move much of the caching functionality into the base Compressor class to be shared. Please do so when you have an actual need to implement another compressor, don't just copy and paste.

Constructor & Destructor Documentation

CompressorZLib()

AZ::IO::CompressorZLib::CompressorZLib	(	unsigned int	decompressionCachePerStream = 64 *1024,
		unsigned int	dataBufferSize = 128 *1024
	)

Parameters

decompressionCachePerStream

cache of decompressed data stored per stream, the more streams you have open the more memory it will use, You can use 0 size too to save memory, but every read will happen with decompression from the closest seek point. That might be fine if we use stream read cache and it matches the size of the seek points (you will need to make sure of that), otherwise the extra cache can be useful. We can convert this system to use pools of caches, but as of now this should be fine.

dataBufferSize

we have one compressor per device, only one stream can read/write at a time and the data buffer is shared for IO operations, the buffer is refCounted and existing only when we read/write compressed streams.

Member Function Documentation

Close()

bool AZ::IO::CompressorZLib::Close ( CompressorStream *  stream )

overridevirtual

Called just before we close the stream. All compression data will be flushed and finalized. (You can't add data afterwards).

Implements AZ::IO::Compressor.

GetTypeId()

AZ::u32 AZ::IO::CompressorZLib::GetTypeId ( ) const

inlineoverridevirtual

Return compressor type id.

Implements AZ::IO::Compressor.

Read()

SizeType AZ::IO::CompressorZLib::Read ( CompressorStream *  stream, SizeType  byteSize, SizeType  offset, void *  buffer  )

overridevirtual

Forwarded function from the Device when we from a compressed stream.

Implements AZ::IO::Compressor.

ReadHeaderAndData()

bool AZ::IO::CompressorZLib::ReadHeaderAndData ( CompressorStream *  stream, AZ::u8 *  data, unsigned int  dataSize  )

overridevirtual

Called when we open a stream to Read for the first time. Data contains the first. dataSize <= m_maxHeaderSize.

Implements AZ::IO::Compressor.

StartCompressor()

bool AZ::IO::CompressorZLib::StartCompressor ( CompressorStream *  stream, int  compressionLevel, SizeType  autoSeekDataSize  )

overridevirtual

Set auto seek point even dataSize bytes.

Reimplemented from AZ::IO::Compressor.

Write()

SizeType AZ::IO::CompressorZLib::Write ( CompressorStream *  stream, SizeType  byteSize, const void *  data, SizeType  offset = SizeType(-1)  )

overridevirtual

Forwarded function from the Device when we write to a compressed stream.

Implements AZ::IO::Compressor.

WriteHeaderAndData()

bool AZ::IO::CompressorZLib::WriteHeaderAndData ( CompressorStream *  stream )

overridevirtual

Called when we are about to start writing to a compressed stream.

Reimplemented from AZ::IO::Compressor.

WriteSeekPoint()

bool AZ::IO::CompressorZLib::WriteSeekPoint ( CompressorStream *  stream )

overridevirtual

Write a seek point.

Reimplemented from AZ::IO::Compressor.

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The documentation for this class was generated from the following file:

• Code/Framework/AzCore/AzCore/IO/CompressorZLib.h