zbackup/compression.hh

// Copyright (c) 2012-2013 Konstantin Isakov <ikm@zbackup.org>
// Part of ZBackup. Licensed under GNU GPLv2 or later

#ifndef COMPRESSION_HH_INCLUDED__
#define COMPRESSION_HH_INCLUDED__

#include <string>


// used for encoding or decoding
class EnDecoder {
protected:
  EnDecoder();
  // cannot be copied
  EnDecoder(const 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 Compression {
public:
  virtual ~Compression();

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

  virtual EnDecoder* getEncoder() const =0;
  virtual EnDecoder* getDecoder() const =0;

  // find a compression by name
  // If optional is false, it will either return a valid Compression object or abort
  // the program If optional is true, it will return NULL, if it cannot find the a
  // compression with that name.
  // Don't delete the returned object because it is a shared instance!
  static const Compression* findCompression( const std::string& name, bool optional = false );

  static const Compression* default_compression;

  class iterator {
    friend class Compression;

    const Compression* const* ptr;
    iterator(const Compression* const* ptr);
  public:
    iterator(const iterator& it);
    iterator& operator =(const iterator& it);

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

    bool at_end() const;

    iterator& operator ++();

    const Compression* operator *();
  };
  static iterator begin();
  static iterator end();
};

#endif