tdeedu/kalzium/src/parser.cpp

/***************************************************************************
    copyright            : (C) 2005 by Inge Wallin
    email                : inge@lysator.liu.se
 ***************************************************************************/
/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/


#include <ctype.h>

#include <kdebug.h>

#include "parser.h"


Parser::Parser()
{
    start(TQString());
}


Parser::Parser(const TQString& _str)
{
    start(_str);
}


Parser::~Parser()
{
}


void
Parser::start(const TQString& _str)
{
    m_str = _str;

    if (_str.isNull()) {
	m_index     = -1;
	m_nextChar  = -1;
	m_nextToken = -1;
    }
    else {
	m_index     = 0;
	m_nextChar  = m_str.at(0).latin1();
	getNextToken();
    }
}


// ----------------------------------------------------------------


// Skip whitespace, and try to parse the following characters as an int.
//
// Return true if successful.  

bool
Parser::parseInt(int *_result)
{
    int  sign = 1;

    skipWhitespace();

    if (m_nextChar == '-') {
	sign = -1;
	getNextChar();
    }

    if (!isdigit(m_nextChar))
	return false;

    int  result = 0;
    while (isdigit(m_nextChar)) {
	result = result * 10 + (m_nextChar - '0');
	getNextChar();
    }

    *_result = sign * result;
    return true;
}


// Skip whitespace, and try to parse the following characters as a
// simple float of the type -?[0-9]+'.'?[0-9]*
//
// Return true if successful.  

bool
Parser::parseSimpleFloat(double *_result)
{
    double  sign = 1.0;

    skipWhitespace();
    if (m_nextChar == '-') {
	sign = -1.0;
	getNextChar();
    }

    if (!isdigit(m_nextChar))
	return false;

    double  result = 0.0;

    // The integer.
    while (isdigit(m_nextChar)) {
	result = result * 10.0 + (double) (m_nextChar - '0');
	getNextChar();
    }
    *_result = result;

    if (m_nextChar != '.' || !isdigit(getNextChar())) {
	*_result = sign * result;
	return true;
    }
	
    double  decimal = 0.1;
    while (isdigit(m_nextChar)) {
	result += decimal * (double) (m_nextChar - '0');
	decimal /= 10.0;
	getNextChar();
    }

    *_result = sign * result;
    return true;
}


// ----------------------------------------------------------------
//                           protected methods


int
Parser::getNextChar()
{
    if (m_index == -1)
	return -1;

    // If end of string, then reset the parser.
    if (m_index == (int) m_str.length()) {
	m_index    = -1;
	m_nextChar = -1;
    }
    else 
	m_nextChar = m_str.at(++m_index).latin1();

    // Take care of null-terminated strings.
    if (m_nextChar == 0) {
	m_index    = -1;
	m_nextChar = -1;
    }

    //kdDebug() << "Parser::getNextChar(): char = " << m_nextChar << endl;

    return m_nextChar;
}


int
Parser::skipWhitespace()
{
    while (TQChar(m_nextChar).isSpace())
	getNextChar();

    return m_nextChar;
}


// Get the next token.  This corresponds to the lexical analyzer of a
// standard parser, e.g as generated by lex.
//
// This basic parser supports integers and simple
// floats.  Reimplement this method to extend it.

int
Parser::getNextToken()
{
    int  saveIndex = m_index;

    skipWhitespace();
    if (isdigit(nextChar())) {
	// At this point we know that there is a valid number in the
	// string.  The only question now, is whether it is an int or a
	// float.

	parseInt(&m_intVal);

	skipWhitespace();
	if (nextChar() == '.') {
	    m_index = saveIndex;

	    // No need to check since we already know it is correct.
	    (void) parseSimpleFloat(&m_floatVal);
	    m_nextToken = FLOAT_TOKEN;
	}
	else
	    m_nextToken = INT_TOKEN;
    }

    else if (nextChar() != -1) {
	// Any character.
	m_nextToken = nextChar();
	getNextChar();
    }

    else
	// End of string.
	m_nextToken = -1;

    return m_nextToken;
}