inputstream.cpp

用于词法分析的词法分析器

/*
  $Id: InputStream.cpp,v 1.2 1997/02/02 02:10:36 matt Exp $

  Input streams class.
  
  Provides higher-level view of an istream-derived object, including
  line, column information and meta-state information (word boundary,
  line end, etc.)
  
  (c) Jan 96 Matt Phillips.
  */

#include <ctype.h>

#include "InputStream.h"

InputStream::InputStream (istream &s, string &fname)
  : str (s), filename (fname), current ('\n'), line (0)
{
  get ();			// sets line & col
}

InputStream::InputStream (istream &s)
  : str (s), current ('\n'), line (0)
{
  get ();			// sets line & col
}

InputStream::InputStream (const InputStream &s) :
  str (s.str), line (s.line), col (s.col), filename (s.filename),
  current (s.current), prev (s.prev)
{
}

void InputStream::get ()
{
  if (!eof ())
  {
    prev = current;
    current = doPeek ();
    str.get ();
  
    // update line, col
    if (!eof ())
    {
      if (prev == '\n')
      {
	line++;
	col = 1;
      } else
	col++;
    }
  }
}

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

  // word boundary
  if ((isalnum (prev) != 0) !=
      (current != InputStream::EOFChar && isalnum (current) != 0))
    state |= InputStream::stWdBoundary;

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

  // beginning of line
  if (col == 1)
    state |= stBegLine;

  return state;
}