gzstream.hpp

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// ============================================================================
// gzstream, C++ iostream classes wrapping the zlib compression library.
// Copyright (C) 2001  Deepak Bandyopadhyay, Lutz Kettner
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
// ============================================================================
//
// File          : gzstream.h
// Revision      : $Revision: 1.5 $
// Revision_date : $Date: 2002/04/26 23:30:15 $
// Author(s)     : Deepak Bandyopadhyay, Lutz Kettner
//
// Standard streambuf implementation following Nicolai Josuttis, "The
// Standard C++ Library".
// ============================================================================
//
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// That's all there is to it!
//
// 10Oct16: Mark C. Miller:
//    * Modified to build in MFEM source tree and use 'mfem' namespace
//    * Modified to use char *mode for constructors/open instead of int
//    * Changed bufferSize from 47+256 to 8192 (8 kilobytes)
//    * Other notes:
//        * consider mode char options for zlib's internal buffer sizes


#ifndef MFEM_GZSTREAM_H
#define MFEM_GZSTREAM_H

#include "../config/config.hpp"

// standard C++ with new header file names and std:: namespace
#include <iostream>
#ifdef MFEM_USE_GZSTREAM
#include <zlib.h>
#endif

namespace mfem
{

// ----------------------------------------------------------------------------
// Internal classes to implement gzstream. See below for user classes.
// ----------------------------------------------------------------------------

#ifdef MFEM_USE_GZSTREAM
class gzstreambuf : public std::streambuf
{
private:
   static const int bufferSize = 8192;    // size of data buff
   // totals 512 bytes under g++ for igzstream at the end.

   gzFile           file;               // file handle for compressed file
   char             buffer[bufferSize]; // data buffer
   char             opened;             // open/close state of stream
   char             mode[16];           // I/O mode chars

   int flush_buffer();
public:
   gzstreambuf() : opened(0)
   {
      setp( buffer, buffer + (bufferSize-1));
      setg( buffer + 4,     // beginning of putback area
            buffer + 4,     // read position
            buffer + 4);    // end position
      // ASSERT: both input & output capabilities will not be used together
   }
   int is_open() { return opened; }
   gzstreambuf* open(char const *name, char const *mode);
   gzstreambuf* close();
   ~gzstreambuf() { close(); }

   virtual int     overflow( int c = traits_type::eof());
   virtual int     underflow();
   virtual int     sync();
};

class gzstreambase : virtual public std::ios
{
protected:
   gzstreambuf buf;
public:
   gzstreambase() { init(&buf); }
   gzstreambase(char const * name, char const *mode);
   ~gzstreambase();
   void open(char const * name, char const *mode);
   void close();
   gzstreambuf* rdbuf() { return &buf; }
};

// ----------------------------------------------------------------------------
// User classes. Use igzstream and ogzstream analogously to ifstream and
// ofstream respectively. They read and write files based on the gz*
// function interface of the zlib. Files are compatible with gzip compression.
// ----------------------------------------------------------------------------

class igzstream : public gzstreambase, public std::istream
{
public:
   igzstream() : std::istream( &buf) {}
   /** Constructs a gzip compressed input stream object and opens
       the associated file. The mode chars are as in gzopen(),
       https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/zlib-gzopen-1.html.
       Default mode is "rb". */
   igzstream(char const * name, char const *mode = "rb")
      : gzstreambase(name, mode), std::istream( &buf) {}
   gzstreambuf* rdbuf() { return gzstreambase::rdbuf(); }
   /** Opens a gzip compressed input stream. The mode chars are as in gzopen(),
       https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/zlib-gzopen-1.html.
       Default mode is "rb". */
   void open(char const * name, char const *mode = "rb")
   {
      gzstreambase::open(name, mode);
   }
};
#endif

class ifgzstream : public std::istream
{
public:
   /** Simple replacement for class @c std::ifstream that automatically detects
       compressed files in gzip format and transparently uncompresses them.
       Internally, the classes @c std::filebuf or @ref gzstreambuf are used to
       handle the file I/O. Reading compressed files requires the MFEM
       build-time option MFEM_USE_GZSTREAM.
       @note For uncompressed files, the @a mode option is ignored and the file
       is opened with @c std::ios_base::in mode.
       @see @ref ofgzstream,
       https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/zlib-gzopen-1.html. */
   ifgzstream(char const *name, char const *mode = "rb");
   ~ifgzstream() { delete buf; }

protected:
   std::streambuf *buf;
   static bool maybe_gz(const char *fn);
};

#ifdef MFEM_USE_GZSTREAM
class ogzstream : public gzstreambase, public std::ostream
{
public:
   ogzstream() : std::ostream( &buf) {}
   /** Constructs a gzip compressed output stream object and opens
       the associated file. The mode chars are as in gzopen(),
       https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/zlib-gzopen-1.html.
       Default mode is "wb6". */
   ogzstream(char const * name, char const *mode = "wb6")
      : gzstreambase(name, mode), std::ostream( &buf) {}
   gzstreambuf* rdbuf() { return gzstreambase::rdbuf(); }
   /** Opens a gzip compressed output stream. The mode chars are as in gzopen(),
       https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/zlib-gzopen-1.html.
       Default mode is "wb6". */
   void open(char const * name, char const *mode = "wb6")
   {
      gzstreambase::open(name, mode);
   }
};
#endif

class ofgzstream : public std::ostream
{
public:
   static char const *default_mode; // defined in gzstream.cpp

   /** Simple replacement for class @c std::ofstream that can transparently
       create files compressed in gzip format (when @a mode contains the
       character @c 'z') or regular uncompressed files. Internally, the classes
       @c std::filebuf or @ref gzstreambuf are used to handle the file I/O.
       The mode chars are as in gzopen() with additional caveat that presence of
       a @c 'z' character indicates desire to compress. Default mode is "zwb6".
       Writing compressed files requires the MFEM build-time option
       MFEM_USE_GZSTREAM.
       @note For uncompressed files, the @a mode option is ignored and the file
       is opened with @c std::ios_base::out mode.
       @see @ref ifgzstream,
       https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/zlib-gzopen-1.html. */
   ofgzstream(char const *name, char const *mode = default_mode);

   ~ofgzstream() { delete buf; }

protected:
   std::streambuf *buf;
};

} // namespace mfem

#endif // MFEM_GZSTREAM_H