zbackup/compression.hh

// Copyright (c) 2012-2014 Konstantin Isakov <ikm@zbackup.org> and ZBackup contributors, see CONTRIBUTORS
// Part of ZBackup. Licensed under GNU GPLv2 or later + OpenSSL, see LICENSE

#ifndef COMPRESSION_HH_INCLUDED
#define COMPRESSION_HH_INCLUDED

#include "sptr.hh"
#include "ex.hh"
#include "nocopy.hh"
#include "config.hh"

namespace Compression {

DEF_EX( Ex, "Compression exception", std::exception )
DEF_EX_STR( exUnsupportedCompressionMethod, "Unsupported compression method:", Ex )

// used for encoding or decoding
class EnDecoder: NoCopy
{
protected:
  EnDecoder();
public:
  virtual ~EnDecoder();

  // encoder can read up to size bytes from data
  virtual void setInput ( const void * data, size_t size ) = 0;
  // how many bytes of the last input haven't been used, yet?
  virtual size_t getAvailableInput() = 0;

  // encoder can write up to size bytes to output
  virtual void setOutput( void * data, size_t size ) = 0;
  // how many bytes of free space are remaining in the output buffer
  virtual size_t getAvailableOutput() = 0;

  // process some bytes
  // finish: will you pass more data to the encoder via setOutput?
  // NOTE You must eventually set finish to true.
  // returns, whether all output bytes have been written
  virtual bool process( bool finish ) = 0;
};

// compression method
class CompressionMethod
{
public:
  virtual ~CompressionMethod();

  // returns name of compression method
  // This name is saved in the file header of the compressed file.
  virtual std::string getName() const = 0;

  virtual sptr< EnDecoder > createEncoder( Config const & ) const = 0;
  virtual sptr< EnDecoder > createEncoder() const = 0;
  virtual sptr< EnDecoder > createDecoder() const = 0;

  // find a compression by name
  // If optional is false, it will either return a valid CompressionMethod
  // object or abort the program. If optional is true, it will return
  // NULL, if it cannot find the a compression with that name.
  static const_sptr< CompressionMethod > findCompression(
    const std::string & name, bool optional = false );

  static const_sptr< CompressionMethod > selectedCompression;

  static const_sptr< CompressionMethod > const compressions[];

  class iterator
  {
    friend class CompressionMethod;

    const const_sptr< CompressionMethod > * ptr;
    iterator( const const_sptr< CompressionMethod > * ptr );
  public:
    iterator( const iterator & it );
    iterator & operator =( const iterator & it );

    bool operator == ( const iterator & other ) const;
    bool operator != ( const iterator & other ) const;

    bool atEnd() const;

    iterator & operator ++();

    const_sptr< CompressionMethod > operator * ();
  };
  static iterator begin();
  static iterator end();
};

}

#endif