xinputstream.cpp

用于词法分析的词法分析器

/* $Id: XInputStream.cpp,v 1.10 1997/04/14 12:31:42 matt Exp $
   
   Extended C++ input streams class.
   
   (c) June 96 Matt Phillips. */

#include <util/checks.h>
#include "XInputStream.h"

void XInputStream::BacktrackMark::mark (XInputStream &stream)
{
  TextMark::mark (stream);
  line = stream.line;
  column = stream.column;
  stream.markSet.set (index);
}

int XInputStream::TextMark::isValid (const XInputStream &stream) const
{
  if (index <= stream.indexLast &&
      index > stream.indexCurrent - stream.buffSize ())
    return 1;
  else
    return 0;
}

void XInputStream::BacktrackMark::jump (XInputStream &stream) const
{
  // sanity check
  CHECK (isValid (stream), "invalid mark used in jump");
  
  stream.indexCurrent = index;
  stream.current = *(stream.indexToPtr (index));
  stream.line = line;
  stream.column = column;
}

// create an XInputStream with an associated file name.
XInputStream::XInputStream (istream &s, const string &fname) :
  input (s), filename (fname)
{
  init ();
}

XInputStream::XInputStream (istream &s) : input (s)
{
  init ();
}

int XInputStream::buffSize () const
{
  if (indexCurrent < MaxBuffSize)
    return indexCurrent + 1;
  else
    return MaxBuffSize - (indexLast - indexCurrent);
}

void XInputStream::init ()
{
  // setup buffer
  buff = new char [MaxBuffSize];
  indexCurrent = indexLast = 0;
  line = column = 0;

  buff [MaxBuffSize - 1] = '\0'; // for peekPrev ()
  int chr = input.get ();

  current = buff [0] = ((chr == EOF) ? '\0' : chr);
}

XInputStream::~XInputStream ()
{
  delete buff;
}

char XInputStream::peekPrev () const
{
  if (indexCurrent % MaxBuffSize == 0)
    return buff [MaxBuffSize - 1];
  else
    return buff [indexCurrent - 1];
}

char XInputStream::get ()
{
  if (!eof ())
  {
    char prev = current;

    if (indexCurrent < indexLast)
    {
      indexCurrent++;
      current = *(indexToPtr (indexCurrent));
    } else
    {
      int chr = input.get ();

      indexCurrent++;
      indexLast = indexCurrent;

      if (chr == EOF)
	chr = 0;

      current = *(indexToPtr (indexCurrent)) = (char)chr;

      if (indexCurrent >= MaxBuffSize)
	markSet.slide ();
    }
    
    // do line/column tracking
    if (prev == '\n')
    {
      line++;
      column = 0;
    } else if (prev == '\t')
      column += 8 - (column % 8);
    else
      column++;
  }

  return peek ();
}

void XInputStream::getText (string &text,
			    const XInputStream::TextMark &start,
			    const XInputStream::TextMark &end) const
{
  CHECK (start.isValid (*this) && end.isValid (*this),
	 "invalid mark(s) used in getText");

  if (start.index <= end.index)
    text.assign (indexToPtr (start.index), end.index - start.index);
  else
    text.assign (indexToPtr (end.index), start.index - end.index);
}

unsigned XInputStream::getState () const
{
  unsigned state = stClear;

  // word boundary
  if ((isalnum (peekPrev ())) !=
      (!eof () && isalnum (peek ()) != 0))
    state |= stWordEdge;

  // end of line
  if (peek () == '\n' || eof ())
    state |= stEndLine;

  // beginning of line
  if (column == 0)
    state |= stStartLine;

  // eof
  if (eof ())
    state |= stEOF;

  return state;
}

template class SlidingBitset<XInputStream::MaxBuffSize>;