/* 
 * Character stream handler : header file
 * 
 */

#include <fstream>
#include <stack>

using namespace std;

const char EOF_CHAR = EOF;
const char L_CURLY  = '{';
const char R_CURLY  = '}';
const char BLANK    = ' ';
const char TAB      = '\t';
const char EOL_CHAR = '\0';
const char VALID_CHARS[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890.,;:<>/*[]+-=(){\t ";

class CharStream : protected ifstream
{
   private:

      int  Current_Char;	 // index of the current character in line buffer
      bool fOpened;		 // true if the stream is open

      void SkipWhite(void);
      void SkipComment(void);      
      void GetNewLine();
      void Advance(void);
      bool Valid(char c);

      
      stack<char> CharStack;
      
   public:

      CharStream();
      CharStream(const char filename[]);
      virtual ~CharStream();

      bool Open(const char filename[]);
      void Close(void);

      char CurrentChar(void);

      void Push_back(char LookAhead);      
};