gzstream.h

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/**
 * \author mdejong
 */
 
// ============================================================================
// 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".
// ============================================================================
 
#ifndef GZSTREAM_H
#define GZSTREAM_H 1
 
// standard C++ with new header file names and std:: namespace
#include <iostream>
#include <fstream>
#include <zlib.h>
#include <string>
#include <string.h>
 
#ifdef GZSTREAM_NAMESPACE
namespace GZSTREAM_NAMESPACE {
#endif
 
  // ----------------------------------------------------------------------------
  // Internal classes to implement gzstream. See below for user classes.
  // ----------------------------------------------------------------------------
 
  class gzstreambuf : public std::streambuf {
  private:
    static const int bufferSize = 47+256;    // 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
    int              mode;               // I/O mode
 
    
    int flush_buffer() {
      // Separate the writing of the buffer from overflow() and
      // sync() operation.
      int w = pptr() - pbase();
      if ( gzwrite( file, pbase(), w) != w)
        return EOF;
      pbump( -w);
      return w;
    }
  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() const { return opened; }
 
    ~gzstreambuf() { close(); }
    gzstreambuf* open( const char* name, int open_mode) {
      if ( is_open())
        return (gzstreambuf*)0;
      mode = open_mode;
      // no append nor read/write mode
      if ((mode & std::ios::ate) || (mode & std::ios::app)
          || ((mode & std::ios::in) && (mode & std::ios::out)))
        return (gzstreambuf*)0;
      char  fmode[10];
      char* fmodeptr = fmode;
      if ( mode & std::ios::in)
        *fmodeptr++ = 'r';
      else if ( mode & std::ios::out)
        *fmodeptr++ = 'w';
      *fmodeptr++ = 'b';
      *fmodeptr = '\0';
      file = gzopen( name, fmode);
      if (file == 0)
        return (gzstreambuf*)0;
      opened = 1;
      setg( buffer + 4,     // beginning of putback area
            buffer + 4,     // read position
            buffer + 4);    // end position      
      return this;
    }
    
    gzstreambuf * close() {
      if ( is_open()) {
        sync();
        opened = 0;
        if ( gzclose( file) == Z_OK)
          return this;
      }
      return (gzstreambuf*)0;
    }
    
    virtual int underflow() { // used for input buffer only
      if ( gptr() && ( gptr() < egptr()))
        return * reinterpret_cast<unsigned char *>( gptr());
        
      if ( ! (mode & std::ios::in) || ! opened)
        return EOF;
      // Josuttis' implementation of inbuf
      int n_putback = gptr() - eback();
      if ( n_putback > 4)
        n_putback = 4;
      memcpy( buffer + (4 - n_putback), gptr() - n_putback, n_putback);
        
      int num = gzread( file, buffer+4, bufferSize-4);
      if (num <= 0) // ERROR or EOF
        return EOF;
        
      // reset buffer pointers
      setg( buffer + (4 - n_putback),   // beginning of putback area
            buffer + 4,                 // read position
            buffer + 4 + num);          // end of buffer
        
      // return next character
      return * reinterpret_cast<unsigned char *>( gptr());    
    }
    
    virtual int overflow( int c=EOF) { // used for output buffer only
      if ( ! ( mode & std::ios::out) || ! opened)
        return EOF;
      if (c != EOF) {
        *pptr() = c;
        pbump(1);
      }
      if ( flush_buffer() == EOF)
        return EOF;
      return c;
    }
    
    virtual int sync() {
      // Changed to use flush_buffer() instead of overflow( EOF)
      // which caused improper behavior with std::endl and flush(),
      // bug reported by Vincent Ricard.
      if ( pptr() && pptr() > pbase()) {
        if ( flush_buffer() == EOF)
          return -1;
      }
      return 0;
    }    
  };
 
  class gzstreambase : virtual public std::ios {
  protected:
    gzstreambuf buf;
  public:
    
    gzstreambase() { init(&buf); }
    gzstreambase( const char* name, int mode) {
      init( &buf);
      open( name, mode);
    }
    ~gzstreambase() {
      buf.close();
    }
    void open( const char* name, int open_mode) {
      if ( ! buf.open( name, open_mode))
        clear( rdstate() | std::ios::badbit);
    }
    
    void close() {
      if ( buf.is_open()) {
        if ( ! buf.close())
          clear( rdstate() | std::ios::badbit );
        else
          clear();
      }
    }
    gzstreambuf* rdbuf() { return &buf; }
    bool is_open() const { return buf.is_open(); }
  };
 
  // ----------------------------------------------------------------------------
  // 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) {} 
    igzstream( const char* name, int open_mode = std::ios::in)
      : gzstreambase( name, open_mode), std::istream( &buf) {}  
    void open( const char* name, int open_mode = std::ios::in) {
      gzstreambase::open( name, open_mode);
    }
  };
 
  class ogzstream : public gzstreambase, public std::ostream {
  public:
    ogzstream() : std::ostream( &buf) {}
    ogzstream( const char* name, int mode = std::ios::out)
      : gzstreambase( name, mode), std::ostream( &buf) {}  
    void open( const char* name, int open_mode = std::ios::out) {
      gzstreambase::open( name, open_mode);
    }
  };
 
#ifdef GZSTREAM_NAMESPACE
} // namespace GZSTREAM_NAMESPACE
#endif
 
#endif // GZSTREAM_H
// ============================================================================
// EOF //