C++ putback函数代码示例

bool Parser::hasOpt(string const l)
{
	// An optional argument can occur in any of the following forms:
	// - \foo[bar]
	// - \foo [bar]
	// - \foo
	//   [bar]
	// - \foo %comment
	//   [bar]

	// remember current position
	unsigned int oldpos = pos_;
	// skip spaces and comments
	while (good()) {
		get_token();
		if (isParagraph()) {
			putback();
			break;
		}
		if (curr_token().cat() == catSpace ||
		    curr_token().cat() == catNewline ||
		    curr_token().cat() == catComment)
			continue;
		putback();
		break;
	}
	bool const retval = (next_token().asInput() == l);
	pos_ = oldpos;
	return retval;
}

S32 LLSDNotationParser::parseMap(std::istream& istr, LLSD& map) const
{
	// map: { string:object, string:object }
	map = LLSD::emptyMap();
	S32 parse_count = 0;
	char c = get(istr);
	if(c == '{')
	{
		// eat commas, white
		bool found_name = false;
		std::string name;
		c = get(istr);
		while(c != '}' && istr.good())
		{
			if(!found_name)
			{
				if((c == '\"') || (c == '\'') || (c == 's'))
				{
					putback(istr, c);
					found_name = true;
					int count = deserialize_string(istr, name, mMaxBytesLeft);
					if(PARSE_FAILURE == count) return PARSE_FAILURE;
					account(count);
				}
				c = get(istr);
			}
			else
			{
				if(isspace(c) || (c == ':'))
				{
					c = get(istr);
					continue;
				}
				putback(istr, c);
				LLSD child;
				S32 count = doParse(istr, child);
				if(count > 0)
				{
					// There must be a value for every key, thus
					// child_count must be greater than 0.
					parse_count += count;
					map.insert(name, child);
				}
				else
				{
					return PARSE_FAILURE;
				}
				found_name = false;
				c = get(istr);
			}
		}
		if(c != '}')
		{
			map.clear();
			return PARSE_FAILURE;
		}
	}
	return parse_count;
}

    bool Scanner::scanInt (char c, Parser& parser, bool& cont)
    {
        assert(c != '\0');
        std::string value;
        value += c;

        bool error = false;

        while (get (c))
        {
            if (std::isdigit (c))
            {
                value += c;
            }
            else if (c!='-' && isStringCharacter (c))
            {
                error = true;
                value += c;
            }
            else if (c=='.')
            {
                if (error)
                {
                    putback (c);
                    break;
                }
                return scanFloat (value, parser, cont);
            }
            else
            {
                putback (c);
                break;
            }
        }

        if (error)
        {
            /// workaround that allows names to begin with digits
            /// \todo disable
            TokenLoc loc (mLoc);
            mLoc.mLiteral.clear();
            cont = parser.parseName (value, loc, *this);
            return true;
//            return false;
        }

        TokenLoc loc (mLoc);
        mLoc.mLiteral.clear();

        std::istringstream stream (value);

        int intValue = 0;
        stream >> intValue;

        cont = parser.parseInt (intValue, loc, *this);
        return true;
    }

dofile()
	{

	char  word[WORDSIZE], *wp;
	char  cmd[WORDSIZE] , sub[WORDSIZE] ;
	int   n ;

	log_lev++;   /* one file deeper */
	pen = G_MOVE ;    /* pick up the pen for each new file. */

	while ( (n = getword(word, W_MUST)) > 0) {

		*cmd = 0;
		*sub = 0;

		/* see if it is a system call out */
		if (n == SYS_W || n == SIN_W) {
			/* so shell gets replaced */
			char *ex = "exec " ;
			/* char *ex = "" ;	*/

			strcpy(word, ex);
			wp = (word + strlen(ex)) ;

			(void)getword(wp, W_LITR) ; /*collect litteral string*/

			docmd("sys" , (n==SIN_W ? "in" : "") , word);
			}

		/* see if it is a command */
		else if (*word == cmd_char) {
			wp = word + 1;
			if (!mkcmd(wp, cmd, sub)) continue;

			/* get the (possible) argument */
			(void)getword(word, W_ANY ) ;

			/* got a command, so no arg */
			if (*word == cmd_char || *word == sys_char) { 
				putback(word);
				*word = 0;       /* null argument */
				}

			/* interpret the command, if word not used, putback */
			if (docmd(cmd, sub, word) == DOBACK) putback(word);
			}


		/* a number or some word that we don't care about */
		else {
			docmd("" , "" , word);
			}

		}/* of loop through file */

	log_lev--;        /* back from a file depth */
	}/* of dofile */

/* Interpret a single statement or block of code. When
   interp_block() returns from its initial call, the final
   brace (or a return) in main() has been encountered.
*/
void interp_block(void)
{
  int value;
  char block = 0;

  do {
    token_type = get_token();

    /* If interpreting single statement, return on
       first semicolon.
    */

    /* see what kind of token is up */
    if(token_type == IDENTIFIER) {
      /* Not a keyword, so process expression. */
      putback();  /* restore token to input stream for
                     further processing by eval_exp() */
      eval_exp(&value);  /* process the expression */
      if(*token!=';') sntx_err(SEMI_EXPECTED);
    }
    else if(token_type==BLOCK) { /* if block delimiter */
      if(*token == '{') /* is a block */
        block = 1; /* interpreting block, not statement */
      else return; /* is a }, so return */
    }
    else /* is keyword */
      switch(tok) {
        case CHAR:
        case INT:     /* declare local variables */
          putback();
          decl_local();
          break;
        case RETURN:  /* return from function call */
          func_ret();
          return;
        case IF:      /* process an if statement */
          exec_if();
          break;
        case ELSE:    /* process an else statement */
          find_eob(); /* find end of else block
                         and continue execution */
          break;
        case WHILE:   /* process a while loop */
          exec_while();
          break;
        case DO:      /* process a do-while loop */
          exec_do();
          break;
        case FOR:     /* process a for loop */
          exec_for();
          break;
        case END:
          exit(0);
      }
  } while (tok != FINISHED && block);
}

    bool Scanner::scanName (char c, std::string& name)
    {
        bool first = false;
        bool error = false;

        name.clear();

        putback (c);

        while (get (c))
        {
            if (!name.empty() && name[0]=='"')
            {
                if (c=='"')
                {
                    name += c;
                    break;
                }
// ignoring escape sequences for now, because they are messing up stupid Windows path names.
//                else if (c=='\\')
//                {
//                    if (!get (c))
//                    {
//                        mErrorHandler.error ("incomplete escape sequence", mLoc);
//                        break;
//                    }
//                }
                else if (c=='\n')
                {
                    mErrorHandler.error ("incomplete string or name", mLoc);
                    break;
                }
            }
            else if (!(c=='"' && name.empty()))
            {
                if (!(std::isalpha (c) || std::isdigit (c) || c=='_' || c=='`' ||
                    /// \todo add an option to disable the following hack. Also, find out who is
                    /// responsible for allowing it in the first place and meet up with that person in
                    /// a dark alley.
                    (c=='-' && !name.empty() && std::isalpha (mStream.peek()))))
                {
                    putback (c);
                    break;
                }

                if (first && std::isdigit (c))
                    error = true;
            }

            name += c;
            first = false;
        }

        return !error;
    }

TokenTypes Scanner::handleSlash( Token * tok )
{
    TokenTypes  result;
    int         current = nextch();

    if( current == S_ENDC ) {
        HCWarning( RTF_BADEOF, _source->name() );
        result = TOK_END;
    } else if( current == '*' ) {

        // Certain RTF commands begin with "\*\", not "\".

        current = nextch();
        if( current != '\\' ) {
            HCWarning( RTF_BADCOMMAND, _lineNum, _source->name() );
            if( current != S_ENDC ) {
                putback( current );
            }
            result = TOK_NONE;
        } else {
            result = handleSlash( tok );
        }
    } else if( current == '\n' ) {

        // A "\" just before a new-line is the same as "\par".

        memcpy( tok->_text, "par", 4 );
        result = TOK_COMMAND;
        ++_lineNum;
    } else if( isSpecial( current ) ) {

        // Some characters are escaped, like "\{".

        result = TOK_SPEC_CHAR;
        tok->_value = current;
    } else if( current == '\'' ) {

        // "\'nnn" signifies the byte with value nnn.

        result = TOK_SPEC_CHAR;
        pullHex( tok );
    } else if( islower( current ) ) {

        // All RTF commands are in lower case.

        putback( current );
        result = TOK_COMMAND;
        pullCommand( tok );
    } else {
        HCWarning( RTF_BADCOMMAND, _lineNum, _source->name() );
        result = TOK_NONE;
    }
    return( result );
}

    bool Scanner::scanName (char c, std::string& name)
    {
        bool first = false;
        bool error = false;

        name.clear();

        putback (c);

        while (get (c))
        {
            if (!name.empty() && name[0]=='"')
            {
                if (c=='"')
                {
                    name += c;
                    break;
                }
// ignoring escape sequences for now, because they are messing up stupid Windows path names.
//                else if (c=='\\')
//                {
//                    if (!get (c))
//                    {
//                        mErrorHandler.error ("incomplete escape sequence", mLoc);
//                        break;
//                    }
//                }
                else if (c=='\n')
                {
                    mErrorHandler.error ("incomplete string or name", mLoc);
                    break;
                }
            }
            else if (!(c=='"' && name.empty()))
            {
                if (!(std::isalpha (c) || std::isdigit (c) || c=='_'))
                {
                    putback (c);
                    break;
                }

                if (first && std::isdigit (c))
                    error = true;
            }

            name += c;
            first = false;
        }

        return !error;
    }

void Scanner::getToken( Token * tok )
{
    int     current;

    while( (current = nextch()) == '\n' ) {
        ++_lineNum;
    }

    tok->_lineNum = _lineNum;
    switch( current ) {
    case S_ENDC:
        tok->_type = TOK_END;
        break;

    case '{':
        tok->_type = TOK_PUSH_STATE;
        break;

    case '}':
        tok->_type = TOK_POP_STATE;
        break;

    case '\\':
        current = nextch();
        if( current == '~' ) {
            tok->_type = TOK_TEXT;
            putback( HARD_SPACE );
            pullText( tok );
        } else {
            putback( current );
            tok->_type = handleSlash( tok );
        }
        break;

    case '\t':
        tok->_type = TOK_COMMAND;
        memcpy( tok->_text, "tab", 4 );
        break;

    default:
        if( isFootnoteChar( current ) ) {
            tok->_type = TOK_SPEC_CHAR;
            tok->_value = current;
        } else {
            tok->_type = TOK_TEXT;
            putback( current );
            pullText( tok );
        }
    }
}

/* Обработка выражения в присваивании */
void eval_exp0(int *value) {
	char temp[ID_LEN];  /* содержит имя переменной,
                         которой присваивается значение */
	register int temp_tok;
	if(token_type == IDENTIFIER) {
		if(is_var(token)) {
			/* если эта переменная,
			                      посмотреть, присваивается ли ей значение */
			if(is_arr(token)) {
				sntx_err(SYNTAX); // todo: make message: redefinition of array is illegal
			}
			strcpy(temp, token);
			temp_tok = token_type;
			get_token();
			if(*token == '=') {  /* это присваивание */
				get_token();
				eval_exp0(value);  /* вычислить присваемое значение */
				assign_var(temp, *value);  /* присвоить значение */
				return;
			} else { /* не присваивание */
				putback();  /* востановление лексемы */
				strcpy(token, temp);
				token_type = temp_tok;
			}
		} else if(is_arr(token)) {
			strcpy(temp, token);
			temp_tok = token_type;
			get_token();
			if(*token == '[') {
				get_token();
				eval_exp0(value); // вычисление выражения в [] скобках
				int arr_index = *value;
				get_token(); // '=' or ';'
				if(*token == '=') {  /* это присваивание */
					get_token();
					eval_exp0(value);  /* вычислить присваемое значение */
					assign_arr_element(temp, arr_index, *value);  /* присвоить значение */
					return;
				} else { /* не присваивание */
					putback();  /* востановление лексемы */
					strcpy(token, temp);
					token_type = temp_tok;
				}
			} else {
				sntx_err(ASSIGN_ARRAY_ILLEGAL);
			}
		}
	}
	eval_exp1(value);
}

/* Process an assignment expression */
void eval_exp0(int *value)
{
  char temp[ID_LEN];  /* holds name of var receiving
                         the assignment */
  register int temp_tok;
  if(token_type==IDENTIFIER) {
    if(is_var(token)) {  /* if a var, see if assignment */
      strcpy(temp, token);
      temp_tok = token_type;
      get_token();
      if(*token=='=') {  /* is an assignment */
   get_token();
   eval_exp0(value);  /* get value to assign */
   assign_var(temp, *value);  /* assign the value */
       return;
      }
      else {  /* not an assignment */
   putback();  /* restore original token */
   strcpy(token, temp);
   token_type = temp_tok;
      }
    }
  }
  eval_exp1(value);
}

void eval_exp0(int &value)
{
	char temp[MAX_ID_LEN + 1];

	tok_types temp_tok;

	if (token_type == IDENTIFIER) 
	{
		if (is_var(token)) 
		{
			strcpy(temp, token);
			temp_tok = token_type;
			get_token();
			if (*token == '=') 
			{ 
				get_token();
				eval_exp0(value); 
				assign_var(temp, value); 
				return;
			}
			else 
			{ 
				putback(); 
				strcpy(token, temp);
				token_type = temp_tok;
			}
		}
	}
	eval_exp1(value);
}

/* Processa uma atribuicao */
void Parser::eval_exp1(double *answer) {
  int slot;
  char ttok_type;
  char temp_token[80];

  if (tok_type == VARIAVEL) {
    /* salva token antigo */
    strcpy(temp_token, token);
    ttok_type = tok_type;

    /* calcula o indice da variavel */
    slot = toupper(*token)-'A';

    get_token();
    if (*token != '=') {
      putback(); /* devolve token atual */
      /* restaura token antigo - nenhuma atribuicao */
      strcpy(token, temp_token);
      tok_type = ttok_type;
    }
    else {
      get_token(); /* pega a proxima parte da expressao */
      eval_exp2(answer);
      vars[slot] = *answer;
      return;
    }
  }
  eval_exp2(answer);
}

TObject* Scanner::extractComparator(char c){
	char n = getChar();
	TOKEN_TYPE type;

	string* str = new string(1, c);

	if(n=='='){
		str->append(1, n);

		switch(c){
		case '<':type = LESS_THAN_OR_EQUALS; break;
		case '>':type = GREATER_THAN_OR_EQUALS; break;
		case '=':type = EQUALITY; break;
		}
	}else{
		//put it back otherwise
		putback();

		switch(c){
		case '<':type = LESS_THAN; break;
		case '>':type = GREATER_THAN; break;
		case '=':type = EQUAL_SIGN; break;
		}
	}

	return new TObject(str, type, line, char_line);
}

static int scanch(void) {
	int	c, c2;

	c = next();
	if ('\\' == c) {
		switch (c = next()) {
		case 'a': return '\a';
		case 'b': return '\b';
		case 'f': return '\f';
		case 'n': return '\n';
		case 'r': return '\r';
		case 't': return '\t';
		case 'v': return '\v';
		case '\\': return '\\';
		case '"': return '"' | 256;
		case '\'': return '\'';
		case '0': case '1': case '2':
		case '3': case '4': case '5':
		case '6': case '7':
			for (c2 = 0; isdigit(c) && c < '8'; c = next())
				c2 = c2 * 8 + (c - '0');
			putback(c);
			return c2;
		case 'x':
			return hexchar();
		default:
			cerror("unknown escape sequence: %s", c);
			return ' ';
		}
	}
	else {
		return c;
	}
}