Building a Programing Language – Part I (Creating BrainLess)

#ifndef __BRAINLESS_LEXER__
#define __BRAINLESS_LEXER__
/*
Author : Shakti Misra
All are welcome to use these files, distribute, modify and release. But This notice should be included.
*/

/*This header contains declarations and definitions for class which are used for tokenizing the souce file*/
#include <string>
#include <stdio.h>
#include "Helper.h"
using namespace std;

/*All the tokens should be here. If some one is adding a new token, they have to include it in this token list.*/
enum enmTokens
{
    eRdAndStrVal = 0, //>>
    eDspCurVal = 1, //.
    eExclaimationMark = 2, //!
    eLeftSqrParen = 3, //[
    eRightSqrParen = 4, //]
    eIncrContent = 5, //++
    eDecrContent = 6, //--
    eAddWithNext = 7, //+*
    eSubNext = 8, //-*
    eIncrHead = 9, //*
    eDecrHead = 10, //<
    eIntNumber = 11, //any integer number
    eTokenOver = 12, //Represents that we have reached end of file.
    eUnknown //Any value out side of the above values.
};

/*tokens can have attributes, like a group of characters like "123" is a single number with the
value attribute of 123. This value is held by this class.*/
class TokenAttrib
{
private:
    int m_iVal; //This holds the value of the attribute, currently only supports integer number
    bool m_bAttribSet; //If this is set to "true" then only we know we need to look for m_iVal.

public:
    TokenAttrib():m_bAttribSet(false)//Set default to false
    {m_iVal = -666;}//Giving some absurd but easy to remember number. Helps in debugging.
    void setAttribVal(const int val)//Will set the attribute value and also the bools.
    {
        m_iVal = val;//Set the value
        m_bAttribSet = true;//Do not foreget to make it true.
    }

    int getAttribVal(){return m_iVal;}
    bool isAttribSet(){return m_bAttribSet;}//Check if the attribute is set. Return true if it is set
    void resetAttrib(){m_bAttribSet = false;}//Reset the value.
};

/*This class will get one by one characters from the source file and then
catagorize it according to any of the enmTokens groups.*/
class Lex
{
private:
    char m_szCurChar;
    char m_szPrevChar;
    const string m_sFileName;//Stores the source file name
    const bool m_bWriteTokenTofile;//If we want to create a token file for fun we can create it. Not used still
    string m_sTokenFile;//Token file name.
    enmTokens m_eCurToken;//Type of the current token that is scanned.
    FILE* m_pTokenfile;//Token file name
    FileRead m_fileReader;//This is the reader class. It will help us read the source file.
    TokenAttrib m_tokAttrib;//Store the attributes of the token.

private:
    char getCurrentChar(){return m_szCurChar;}
    
    char getNextChar()
    {
        m_szPrevChar = m_szCurChar;//First store the previous character.
        while(' ' == (m_szCurChar = m_fileReader.getNextChar()))
            ;//NULL body while. This look is to skip spaces.
        return m_szCurChar;
    }
    
    void openTokenFile()
    {
        if(NULL == m_pTokenfile)
            m_pTokenfile = fopen(m_sTokenFile.c_str(), "w");
    }

public:
    Lex(const string sFileName, const bool WriteTokenTofile = false /*Make it default to false.*/):
        m_sFileName(sFileName),
        m_szCurChar(0),
        m_szPrevChar(0),
        m_bWriteTokenTofile(WriteTokenTofile),
        m_eCurToken(eUnknown),
        m_fileReader(m_sFileName)
    {
        m_pTokenfile = NULL;

        if(true == m_bWriteTokenTofile)
        {
            setTokenFileName(m_sFileName);
            openTokenFile();
        }
    }

    ~Lex()
    {
        if(NULL != m_pTokenfile)
        {
            fclose(m_pTokenfile);
            m_pTokenfile = NULL;
        }
    }

    void setTokenFileName(string sFileName)
    {
        m_sTokenFile = sFileName + ".Token";
    }
    
    string getTokenFileName()
    {return m_sTokenFile;}

    enmTokens getNextToken();//Get the next token

    enmTokens getCurrentToken(){return m_eCurToken;}//Get the current token. We do not increment the token here.

    int getAttribVal()
    {return m_tokAttrib.getAttribVal();}//Get the token attribute value here.

};


#endif //__BRAINLESS_LEXER__