www.pudn.com > calc5.zip > Scan.cpp

//------------------------------------ 
//  scan.cpp 
//  (c) Bartosz Milewski, 1994 
//------------------------------------ 
 
#include "scan.h" 
#include "symtab.h" 
#include "params.h" 
 
#include  
#include  
#include  
#include  
#include  
using std::cerr; 
 
Scanner::Scanner (char const * buf) 
: _buf (buf), _iLook (0), _iSymbol (0), _lenSymbol (0) 
{ 
    Accept (); 
} 
 
void Scanner::EatWhite () 
{ 
    while (isspace (_buf[_iLook])) 
        ++_iLook; 
} 
 
int Scanner::GetSymbolName (char * strOut, int lenBuf) 
{ 
    assert (lenBuf > maxSymLen); 
    assert (_lenSymbol < lenBuf); 
 
    strncpy (strOut, &_buf [_iSymbol], _lenSymbol); 
    strOut [_lenSymbol] = 0; 
    return _lenSymbol; 
} 
 
EToken Scanner::Accept () 
{ 
    EatWhite (); 
    switch (_buf[_iLook]) 
    { 
    case '+': 
        _token = tPlus; 
        ++_iLook; 
        break; 
    case '-': 
        _token = tMinus; 
        ++_iLook; 
        break; 
    case '*': 
        _token = tMult; 
        ++_iLook; 
        break; 
    case '/': 
        _token = tDivide; 
        ++_iLook; 
        break; 
    case '(': 
        _token = tLParen; 
        ++_iLook; 
        break; 
    case ')': 
        _token = tRParen; 
        ++_iLook; 
        break; 
    case '=': 
        _token = tAssign; 
        ++_iLook; 
        break; 
    case '0': case '1': case '2': case '3': case '4': 
    case '5': case '6': case '7': case '8': case '9': 
    case '.': 
    { 
        _token = tNumber; 
        char * p; 
        _number = strtod (&_buf [_iLook], &p); 
        _iLook = p - _buf; 
        break; 
    } 
    case 0: // end of input 
        _token = tEnd; 
        break; 
    default: 
        if (isalpha (_buf [_iLook]) || _buf [_iLook] == '_') 
        { 
            _token = tIdent; 
            _iSymbol = _iLook; 
            do { 
                ++_iLook; 
            } while (isalnum (_buf [_iLook])); 
 
            _lenSymbol = _iLook - _iSymbol; 
			if (_lenSymbol > maxSymLen) 
			{ 
				cerr << "Warning: Variable name truncated\n"; 
				_lenSymbol = maxSymLen; 
			} 
        } 
        else 
            _token = tError; 
        break; 
    } 
    return Token (); 
}