pl_streambuf.cc

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// -*- C++ -*-

// PLearn (A C++ Machine Learning Library)
// Copyright (C) 2002 Xavier Saint-Mleux <saintmlx@iro.umontreal.ca>
//

// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// 
//  1. Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
// 
//  2. Redistributions in binary form must reproduce the above copyright
//     notice, this list of conditions and the following disclaimer in the
//     documentation and/or other materials provided with the distribution.
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//  3. The name of the authors may not be used to endorse or promote
//     products derived from this software without specific prior written
//     permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
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// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
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// This file is part of the PLearn library. For more information on the PLearn
// library, go to the PLearn Web site at www.plearn.org


#include "pl_streambuf.h"


using namespace PLearn;
using namespace std;

/*****
 * pl_streambuf
 */

pl_streambuf::pl_streambuf(streambuf& _original_buf, int _inbuflen) 
  :original_buf(_original_buf), inbuf(0), inbuflen(_inbuflen), first_marker(0)
{
  //set minimum size for buffer
  if(inbuflen < pback_size+1)
    inbuflen= min_buf_size + pback_size;

  inbuf= new char[inbuflen];
  setg(inbuf+pback_size, inbuf+pback_size, inbuf+pback_size); // reserve a few bytes for a putback area.
}

pl_streambuf::~pl_streambuf()
{
  if(inbuf)
    delete[] inbuf;
}

pl_streambuf::int_type pl_streambuf::underflow()
{
  //no marker: return get from original buffer.
  if(first_marker == 0 && gptr() == egptr())
    {
      //delete buffer if we have a long one that is not used anymore
      if(inbuflen > min_buf_size + pback_size)
        { //don't keep copy of last char: underlying buf. will be used for putbacks.
          delete[] inbuf;
          inbuflen= min_buf_size + pback_size;
          inbuf= new char[inbuflen];
          setg(inbuf+pback_size, inbuf+pback_size, inbuf+pback_size);
        }
      return original_buf.sgetc();
    }
  
  //marked buffer:

  //return a buffered char if any is available (is this necessary? -xsm)
  if(gptr() < egptr())
    return *gptr(); 

  int oldbuflen= egptr()-inbuf; //< current length used
  //if at end of buffer, make it twice as long as before
  if(egptr() == inbuf+inbuflen)
    {
      //create a new longer buffer
      int newbuflen= inbuflen*2;
      char* newbuf= new char[newbuflen];
      
      //copy from current buf. to new one
      for(int i= 0; i < inbuflen; ++i)
        newbuf[i]= inbuf[i];

      //reposition get pointers
      setg(newbuf+pback_size, newbuf+(gptr()-inbuf), newbuf+inbuflen);
      delete[] inbuf; //< delete prev. buffer
      inbuf= newbuf;  //< point to new buffer
      inbuflen= newbuflen; //< adjust current buffer length
    }
      
  char* the_egptr= 0;  //ptr. to actual end of buf. (not known yet)

  //fill buffer from underlying streambuf
  for(int i= oldbuflen; i < inbuflen; ++i)
    if(original_buf.sgetc() != pl_streambuf::eof && original_buf.in_avail() || i == oldbuflen)
      inbuf[i]= original_buf.sbumpc();  //< get a char from underlying streambuf and advance it's pos.
    else
      { //no input available: stop filling buffer (set egptr at current pos)
        the_egptr= inbuf+i;
        break;
      }

  if(the_egptr == 0) //buf. all filled: set egptr at end of buf.
    the_egptr= inbuf + inbuflen;

  //set pointers into buffer
  setg(eback(), gptr(), the_egptr);
  if(gptr() < egptr()) //< got some new stuff?
    return *gptr();    //< return next char.
  return pl_streambuf::eof; //< at eof: return eof.
}


pl_streambuf::int_type pl_streambuf::uflow()
{
  int c= underflow(); //< get char. at current pos.
  if(first_marker == 0 && gptr() == egptr()) 
    original_buf.sbumpc();  //< no mark: advance pos. of original streambuf
  else
    gbump(1);               //< mark(s): advance pos. in our buffer
  return c;
}

streamsize pl_streambuf::xsgetn(char_type* s, streamsize n)
{
  int_type c= uflow();
  int i;
  for(i= 0; i < n && c != pl_streambuf::eof; ++i)
    {
      s[i]= static_cast<char_type>(c);
      c= uflow();
    }
  return i;
}

streamsize pl_streambuf::xsputn(const char_type* s, streamsize n)
{
  int_type c = 1;
  int i;
  for(i= 0; i < n && c != pl_streambuf::eof; ++i)
    c= overflow(static_cast<int_type>(s[i]));
  return i;
}


pl_streambuf::int_type pl_streambuf::overflow(int_type meta) //trivial overflow
{ return original_buf.sputc(meta); }           //(no marking on output == no buffering)

void pl_streambuf::seekmark(const pl_streammarker& mark)
{ setg(eback(), inbuf+mark.pos, egptr()); } //< set get ptr. to mark position

pl_streambuf::int_type pl_streambuf::sync()
{ // no marking on output: sync underlying streambuf
#if __GNUC__ < 3 && !defined(WIN32)
  return original_buf.sync();
#else
  return original_buf.pubsync();
#endif
}

pl_streambuf::int_type pl_streambuf::pbackfail(int_type c)
{ return original_buf.sungetc(); } //< pback before beginning of our buf: pback in underlying streambuf




/*****
 * pl_streammarker
 */

//ctor. from pl_streambuf: insert self in buf's list of markers and remember current pos.
pl_streammarker::pl_streammarker(pl_streambuf* _buf)
  :buf(_buf), next_marker(buf->first_marker), pos(buf->curpos())
{ buf->first_marker= this; }

//ctor. from any streambuf: just make sure it's a pl_streambuf and construct normally
pl_streammarker::pl_streammarker(streambuf* _buf)
  :buf(dynamic_cast<pl_streambuf*>(_buf))
{
  if(buf == 0)
    PLERROR("Cannot put a pl_streammarker on a streambuf that is not a pl_streambuf...");
  next_marker= buf->first_marker;
  pos= buf->curpos();
  
  buf->first_marker= this; 
}

//destructor: simply remove self from buf's list of markers.
pl_streammarker::~pl_streammarker()
{
  pl_streammarker* prev= 0; 
  for(pl_streammarker* it= buf->first_marker; it != 0; prev= it, it!=0?it= it->next_marker:it= 0)
    if(it == this)
      {
        if(prev == 0)
          buf->first_marker= it->next_marker;
        else
          prev->next_marker= it->next_marker;
        it= 0;
      }
}

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