gzstream.c

一个用来实现偏微分方程中网格的计算库

// ============================================================================
// 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.C
// Revision      : $Revision: 1.1 $
// Revision_date : $Date: 2003-09-16 00:41:29 $
// Author(s)     : Deepak Bandyopadhyay, Lutz Kettner
// 
// Standard streambuf implementation following Nicolai Josuttis, "The 
// Standard C++ Library".
// ============================================================================

// Local includes
#include "gzstream.h"

#ifdef HAVE_ZLIB_H


// System includes
#include <iostream>
#include <string.h>  // for memcpy




#ifdef GZSTREAM_NAMESPACE
namespace GZSTREAM_NAMESPACE {
#endif

// ----------------------------------------------------------------------------
// Internal classes to implement gzstream. See header file for user classes.
// ----------------------------------------------------------------------------

// --------------------------------------
// class gzstreambuf:
// --------------------------------------

gzstreambuf* 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;
    return this;
}

gzstreambuf * gzstreambuf::close() {
    if ( is_open()) {
        sync();
        opened = 0;
        if ( gzclose( file) == Z_OK)
            return this;
    }
    return (gzstreambuf*)0;
}

int gzstreambuf::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());    
}

int gzstreambuf::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;
}

int gzstreambuf::overflow( int c) { // 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;
}

int gzstreambuf::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;
}



/**
 * The following function only works (so far) for reading
 * It was written by John W. Peterson.
 */
gzstreambuf::pos_type gzstreambuf::seekoff(off_type ot,
					   std::ios::seekdir,
					   std::ios::openmode)
{
  // Correlation between C++ and C seek directions
  // std::ios::beg <==> SEEK_SET
  // std::ios::cur <==> SEEK_CUR
  
  pos_type pos = static_cast<pos_type> ( gzseek(file, ot, SEEK_SET) );
  
  // setp() sets the writing pointer.
  // setg() sets the reading pointer.

  // Set the streambuf's internal pointer.
  setg( buffer + pos,
	buffer + pos,
	buffer + pos);
  
  return pos;
}



  
// --------------------------------------
// class gzstreambase:
// --------------------------------------

gzstreambase::gzstreambase( const char* name, int mode) {
    init( &buf);
    open( name, mode);
}

gzstreambase::~gzstreambase() {
    buf.close();
}

void gzstreambase::open( const char* name, int open_mode) {
    if ( ! buf.open( name, open_mode))
        clear( rdstate() | std::ios::badbit);
}

void gzstreambase::close() {
    if ( buf.is_open())
        if ( ! buf.close())
            clear( rdstate() | std::ios::badbit);
}

#ifdef GZSTREAM_NAMESPACE
} // namespace GZSTREAM_NAMESPACE
#endif

// ============================================================================
// EOF //
#endif // HAVE_ZLIB_H