lexer.cpp

LL1通用语法分析器

/************************************************************************
                        Copyright IBMTC Written by Xinxi Wang
**************************************************************************/

#include "Lexer.h"
#include <iostream>
using namespace std;

/**
 * @return bool
 */
bool Lexer::hasNextToken ( )
{
}


/**
 * @return Lexer*
 */
Lexer* Lexer::getInstance ( )
{
    static Lexer s;
    return &s;
}



void Lexer::setFile(const string& file)
{
    in.open(file.c_str(), ios::in);
    getline(in, buffer);
    lineNo = 1;
    columnNo = 0;
    
    getToken();
}

    
/**
 * 返回当前标记，并且从缓冲区里面删除当前标记
 * @return Terminal
 */
Terminal Lexer::nextToken ()
{
    Terminal tmp = currentToken;
    getToken();
    return tmp;
}


void Lexer::getToken()
{
    int t;
    string term;
    
    if(in.eof())
        return;
    
    do{
        while(columnNo < buffer.size() && 
              (buffer.at(columnNo) == ' ' || 
               buffer.at(columnNo) == '\n' || 
               buffer.at(columnNo) == '\t')) columnNo++;
        
        if(columnNo == buffer.size()){
            columnNo = 0;
            lineNo++;
            
            if(!getline(in, buffer)){
                currentToken = Terminal("$");
                return;
            }
        }
        
        t = columnNo;
        
        while(t < buffer.size() && buffer.at(t) != ' ' 
              && buffer.at(t) != '\n' 
              && buffer.at(t) != '\t') t++;
        
        //cerr << columnNo << t - columnNo << endl;
        
        term = buffer.substr(columnNo, t - columnNo);
        
        columnNo = t;
    }while(term.empty());
    
    currentToken = Terminal(term);
}
    

/**
 * 返回当前标记
 */
Terminal Lexer::current()
{
    return currentToken;
}



int Lexer::line()
{
    return lineNo;
}


int Lexer::column()
{
    return columnNo;
}


string Lexer::getBuffer()
{
    return buffer;
}