A class to handle stream deflate on the fly. More...

#include <deflateoutputstreambuf.hpp>

Inheritance diagram for zipios::DeflateOutputStreambuf:

Collaboration diagram for zipios::DeflateOutputStreambuf:

Public Member Functions
	DeflateOutputStreambuf (std::streambuf *outbuf)
	Initialize a DeflateOutputStreambuf object. More...

	DeflateOutputStreambuf (DeflateOutputStreambuf const &src)=delete

virtual	~DeflateOutputStreambuf ()
	Clean up any resources used by this object. More...

void	closeStream ()
	Closing the stream. More...

uint32_t	getCrc32 () const
	Get the CRC32 of the file. More...

size_t	getSize () const
	Retrieve the size of the file deflated. More...

bool	init (FileEntry::CompressionLevel compression_level)
	Initialize the zlib library. More...

DeflateOutputStreambuf &	operator= (DeflateOutputStreambuf const &rhs)=delete

Protected Member Functions
virtual int	overflow (int c=EOF)
	Handle an overflow. More...

virtual int	sync ()
	Synchronize the buffer. More...

Protected Attributes
std::vector< char >	m_invec

std::streambuf *	m_outbuf

uint32_t	m_overflown_bytes = 0

Private Member Functions
void	endDeflation ()
	End deflation of current file. More...

void	flushOutvec ()
	Flush the cached output data. More...

Private Attributes
uint32_t	m_crc32 = 0

std::vector< char >	m_outvec

z_stream	m_zs

bool	m_zs_initialized = false

Detailed Description

DeflateOutputStreambuf is an output stream filter, that deflates the data that is written to it before it passes it on to the output stream it is attached to. Deflation/Inflation is a compression/decompression method used in gzip and zip. The zlib library is used to perform the actual deflation, this class only wraps the functionality in an output stream filter.

Definition at line 47 of file deflateoutputstreambuf.hpp.

Constructor & Destructor Documentation

zipios::DeflateOutputStreambuf::DeflateOutputStreambuf ( std::streambuf * outbuf )

This function initializes the DeflateOutputStreambuf object to make it ready for compressing data using the zlib library.

Parameters

[in,out] outbuf The streambuf to use for output.

Definition at line 57 of file deflateoutputstreambuf.cpp.

References m_zs.

zipios::DeflateOutputStreambuf::DeflateOutputStreambuf ( DeflateOutputStreambuf const & src )

delete

zipios::DeflateOutputStreambuf::~DeflateOutputStreambuf ( )

virtual

The destructor makes sure that the zlib library is done with all the input and output data by calling various flush functions. It then makes sure that the remaining data from zlib is printed in the output file.

This is similar to calling closeStream() explicitly.

Definition at line 87 of file deflateoutputstreambuf.cpp.

References closeStream().

Member Function Documentation

void zipios::DeflateOutputStreambuf::closeStream ( )

This function is expected to be called once the stream is getting closed (the buffer is destroyed.)

It ensures that the zlib library last few bytes get flushed and then mark the class as closed.

Note that this function can be called to close the current zlib library stream and start a new one. It is actually called from the putNextEntry() function (via the closeEntry() function.)

Definition at line 205 of file deflateoutputstreambuf.cpp.

References endDeflation(), m_zs, and m_zs_initialized.

Referenced by zipios::ZipOutputStreambuf::closeEntry(), zipios::GZIPOutputStreambuf::finish(), and ~DeflateOutputStreambuf().

void zipios::DeflateOutputStreambuf::endDeflation ( )

private

This function flushes the remaining data in the zlib buffers, after which the only possible operations are deflateEnd() or deflateReset().

Definition at line 382 of file deflateoutputstreambuf.cpp.

References flushOutvec(), zipios::getBufferSize(), m_outvec, m_overflown_bytes, m_zs, and overflow().

Referenced by closeStream().

void zipios::DeflateOutputStreambuf::flushOutvec ( )

private

This function flushes m_outvec and updates the output pointer and size m_zs.next_out and m_zs.avail_out.

Todo:: We need to redesign the class to allow for STORED files to flow through without the need have this crap of bytes to skip...

Definition at line 351 of file deflateoutputstreambuf.cpp.

References zipios::getBufferSize(), zipios::FilterOutputStreambuf::m_outbuf, m_outvec, and m_zs.

Referenced by endDeflation(), and overflow().

uint32_t zipios::DeflateOutputStreambuf::getCrc32 ( ) const

This function returns the CRC32 for the current file.

The returned value is the CRC for the data that has been compressed already (due to calls to overflow()). As DeflateOutputStreambuf may buffer an arbitrary amount of bytes until closeStream() has been invoked, the returned value is not very useful before closeStream() has been called.

Returns: The CRC32 of the last file that was passed through.

Definition at line 239 of file deflateoutputstreambuf.cpp.

References m_crc32.

Referenced by zipios::ZipOutputStreambuf::updateEntryHeaderInfo(), and zipios::GZIPOutputStreambuf::writeTrailer().

size_t zipios::DeflateOutputStreambuf::getSize ( ) const

This function returns the number of bytes written to the streambuf object and that were processed from the input buffer by the compressor. After closeStream() has been called this number is the total number of bytes written to the stream. In other words, the size of the uncompressed data.

Returns: The uncompressed size of the file that got written here.

Definition at line 256 of file deflateoutputstreambuf.cpp.

References m_overflown_bytes.

Referenced by zipios::ZipOutputStreambuf::updateEntryHeaderInfo(), and zipios::GZIPOutputStreambuf::writeTrailer().

bool zipios::DeflateOutputStreambuf::init ( FileEntry::CompressionLevel compression_level )

This method is called in the constructor, so it must not write anything to the output streambuf m_outbuf (see notice in constructor.)

It will initialize the output stream as required to accept data to be compressed using the zlib library. The compression level is expected to come from the FileEntry which is about to be saved in the file.

Returns: true if the initialization succeeded, false otherwise.

Definition at line 106 of file deflateoutputstreambuf.cpp.

References zipios::FileEntry::COMPRESSION_LEVEL_DEFAULT, zipios::FileEntry::COMPRESSION_LEVEL_FASTEST, zipios::FileEntry::COMPRESSION_LEVEL_MAXIMUM, zipios::FileEntry::COMPRESSION_LEVEL_MINIMUM, zipios::FileEntry::COMPRESSION_LEVEL_NONE, zipios::FileEntry::COMPRESSION_LEVEL_SMALLEST, zipios::getBufferSize(), m_crc32, m_invec, m_outvec, m_zs, and m_zs_initialized.

Referenced by zipios::GZIPOutputStreambuf::GZIPOutputStreambuf(), and zipios::ZipOutputStreambuf::putNextEntry().

DeflateOutputStreambuf& zipios::DeflateOutputStreambuf::operator= ( DeflateOutputStreambuf const & rhs )

delete

int zipios::DeflateOutputStreambuf::overflow ( int c = EOF )

protectedvirtual

This function is called by the streambuf implementation whenever "too many bytes" are in the output buffer, ready to be compressed.

Exceptions

IOException This exception is raised whenever the overflow() function calls a zlib library function which returns an error.

Parameters

[in] c The character (byte) that overflowed the buffer.

Returns: Always zero (0).

Reimplemented in zipios::ZipOutputStreambuf, and zipios::GZIPOutputStreambuf.

Definition at line 275 of file deflateoutputstreambuf.cpp.

References flushOutvec(), zipios::getBufferSize(), m_crc32, m_invec, m_outvec, and m_zs.

Referenced by endDeflation(), zipios::GZIPOutputStreambuf::overflow(), and zipios::ZipOutputStreambuf::overflow().

int zipios::DeflateOutputStreambuf::sync ( )

protectedvirtual

The sync() function is expected to clear the input buffer so that any new data read from the input (i.e. a file) are re-read from disk. However, a call to sync() could break the filtering functionality so we do not implement it at all.

This means you are stuck with the existing buffer. But to make sure the system understands that, we always returns -1.

Reimplemented in zipios::ZipOutputStreambuf, and zipios::GZIPOutputStreambuf.

Definition at line 340 of file deflateoutputstreambuf.cpp.

Referenced by zipios::GZIPOutputStreambuf::sync(), and zipios::ZipOutputStreambuf::sync().