static int quoted_term;
#define quoted_term_char ((unsigned char)quoted_term)
#define WHEN_QUOTED_TERM(x) ((quoted_term >= 0) && (x))
#define QUOTED_TERM_P(c) WHEN_QUOTED_TERM((c) == quoted_term_char)


#define STR_FUNC_ESCAPE 0x01
#define STR_FUNC_EXPAND 0x02
#define STR_FUNC_REGEXP 0x04
#define STR_FUNC_QWORDS 0x08
#define STR_FUNC_INDENT 0x20

enum string_type {
    str_squote = (0),
    str_dquote = (STR_FUNC_EXPAND),
    str_xquote = (STR_FUNC_ESCAPE|STR_FUNC_EXPAND),
    str_regexp = (STR_FUNC_REGEXP|STR_FUNC_ESCAPE|STR_FUNC_EXPAND),
    str_sword  = (STR_FUNC_QWORDS),
    str_dword  = (STR_FUNC_QWORDS|STR_FUNC_EXPAND),
};


#define NEW_STRTERM(func, term, paren) \
	rb_node_newnode(NODE_STRTERM, (func), (term), (paren))


static int
parse_string(quote)
    NODE *quote;
{
    int func = quote->nd_func;
    int term = quote->nd_term;
    int paren = quote->nd_paren;
    int c, space = 0;

    if (func == -1) return tSTRING_END;
    c = nextc();
    if ((func & STR_FUNC_QWORDS) && ISSPACE(c)) {
	do {c = nextc();} while (ISSPACE(c));
	space = 1;
    }
    if (c == term) {
	if (!lex_strnest) {
	  eos:
	    if (func & STR_FUNC_QWORDS) {
		quote->nd_func = -1;
		return ' ';
	    }
	    if (!(func & STR_FUNC_REGEXP)) return tSTRING_END;
	    yylval.num = regx_options();
	    return tREGEXP_END;
	}
    }
    if (c == '\\' && WHEN_QUOTED_TERM(peek(quoted_term_char))) {
	if ((c = nextc()) == term) goto eos;
    }
    if (space) {
	pushback(c);
	return ' ';
    }
    newtok();
    if ((func & STR_FUNC_EXPAND) && c == '#') {
	switch (c = nextc()) {
	  case '$':
	  case '@':
	    pushback(c);
	    return tSTRING_DVAR;
	  case '{':
	    return tSTRING_DBEG;
	}
	tokadd('#');
    }
    pushback(c);
    if (tokadd_string(func, term, paren) == -1) {
	ruby_sourceline = nd_line(quote);
	rb_compile_error("unterminated string meets end of file");
	return tSTRING_END;
    }

    tokfix();
    yylval.node = NEW_STR(rb_str_new(tok(), toklen()));
    return tSTRING_CONTENT;
}

static int
read_escape()
{
    int c;

    switch (c = nextc()) {
      case '\\':	/* Backslash */
	return c;

      case 'n':	/* newline */
	return '\n';

      case 't':	/* horizontal tab */
	return '\t';

      case 'r':	/* carriage-return */
	return '\r';

      case 'f':	/* form-feed */
	return '\f';

      case 'v':	/* vertical tab */
	return '\13';

      case 'a':	/* alarm(bell) */
	return '\007';

      case 'e':	/* escape */
	return 033;

      case '0': case '1': case '2': case '3': /* octal constant */
      case '4': case '5': case '6': case '7':
	{
	    int numlen;

	    pushback(c);
	    c = scan_oct(lex_p, 3, &numlen);
	    lex_p += numlen;
	}
	return c;

      case 'x':	/* hex constant */
	{
	    int numlen;

	    c = scan_hex(lex_p, 2, &numlen);
	    if (numlen == 0) {
		yyerror("Invalid escape character syntax");
		return 0;
	    }
	    lex_p += numlen;
	}
	return c;

      case 'b':	/* backspace */
	return '\010';

      case 's':	/* space */
	return ' ';

      case 'M':
	if ((c = nextc()) != '-') {
	    yyerror("Invalid escape character syntax");
	    pushback(c);
	    return '\0';
	}
	if ((c = nextc()) == '\\') {
	    return read_escape() | 0x80;
	}
	else if (c == -1) goto eof;
	else {
	    return ((c & 0xff) | 0x80);
	}

      case 'C':
	if ((c = nextc()) != '-') {
	    yyerror("Invalid escape character syntax");
	    pushback(c);
	    return '\0';
	}
      case 'c':
	if ((c = nextc())== '\\') {
	    c = read_escape();
	}
	else if (c == '?')
	    return 0177;
	else if (c == -1) goto eof;
	return c & 0x9f;

      eof:
      case -1:
        yyerror("Invalid escape character syntax");
	return '\0';

      default:
	return c;
    }
}

static int
tokadd_escape(term)
    int term;
{
    int c;

    switch (c = nextc()) {
      case '\n':
	return 0;		/* just ignore */

      case '0': case '1': case '2': case '3': /* octal constant */
      case '4': case '5': case '6': case '7':
	{
	    int i;

	    tokadd('\\');
	    tokadd(c);
	    for (i=0; i<2; i++) {
		c = nextc();
		if (c == -1) goto eof;
		if (c < '0' || '7' < c) {
		    pushback(c);
		    break;
		}
		tokadd(c);
	    }
	}
	return 0;

      case 'x':	/* hex constant */
	{
	    int numlen;

	    tokadd('\\');
	    tokadd(c);
	    scan_hex(lex_p, 2, &numlen);
	    if (numlen == 0) {
		yyerror("Invalid escape character syntax");
		return -1;
	    }
	    while (numlen--)
		tokadd(nextc());
	}
	return 0;

      case 'M':
	if ((c = nextc()) != '-') {
	    yyerror("Invalid escape character syntax");
	    pushback(c);
	    return 0;
	}
	tokadd('\\'); tokadd('M'); tokadd('-');
	goto escaped;

      case 'C':
	if ((c = nextc()) != '-') {
	    yyerror("Invalid escape character syntax");
	    pushback(c);
	    return 0;
	}
	tokadd('\\'); tokadd('C'); tokadd('-');
	goto escaped;

      case 'c':
	tokadd('\\'); tokadd('c');
      escaped:
	if ((c = nextc()) == '\\') {
	    return tokadd_escape(term);
	}
	else if (c == -1) goto eof;
	tokadd(c);
	return 0;

      eof:
      case -1:
        yyerror("Invalid escape character syntax");
	return -1;

      default:
	if (c != '\\' || c != term)
	    tokadd('\\');
	tokadd(c);
    }
    return 0;
}

static int
regx_options()
{
    char kcode = 0;
    int options = 0;
    int c;

    newtok();
    while (c = nextc(), ISALPHA(c)) {
	switch (c) {
	  case 'i':
	    options |= RE_OPTION_IGNORECASE;
	    break;
	  case 'x':
	    options |= RE_OPTION_EXTENDED;
	    break;
	  case 'm':
	    options |= RE_OPTION_MULTILINE;
	    break;
	  case 'o':
	    options |= RE_OPTION_ONCE;
	    break;
	  case 'n':
	    kcode = 16;
	    break;
	  case 'e':
	    kcode = 32;
	    break;
	  case 's':
	    kcode = 48;
	    break;
	  case 'u':
	    kcode = 64;
	    break;
	  default:
	    tokadd(c);
	    break;
	}
    }
    pushback(c);
    if (toklen()) {
	tokfix();
	rb_compile_error("unknown regexp option%s - %s",
			 toklen() > 1 ? "s" : "", tok());
    }
    return options | kcode;
}

static int
tokadd_string(func, term, paren)
    int func, term, paren;
{
    int c;

    while ((c = nextc()) != -1) {
	if (paren && c == paren) {
	    lex_strnest++;
	}
	else if (c == term) {
	    if (!lex_strnest) {
		pushback(c);
		break;
	    }
	    --lex_strnest;
	}
	else if ((func & STR_FUNC_EXPAND) && c == '#' && lex_p < lex_pend) {
	    int c2 = *lex_p;
	    if (c2 == '$' || c2 == '@' || c2 == '{') {
		pushback(c);
		break;
	    }
	}
	else if (c == '\\') {
	    c = nextc();
	    if (QUOTED_TERM_P(c)) {
		pushback(c);
		return c;
	    }
	    switch (c) {
	      case '\n':
		continue;

	      case '\\':
		if (func & STR_FUNC_ESCAPE) tokadd(c);
		break;

	      default:
		if (func & STR_FUNC_REGEXP) {
		    pushback(c);
		    if (tokadd_escape(term) < 0)
			return -1;
		    continue;
		}
		else if (func & STR_FUNC_EXPAND) {
		    pushback(c);
		    if (func & STR_FUNC_ESCAPE) tokadd('\\');
		    c = read_escape();
		}
		else if ((func & STR_FUNC_QWORDS) && ISSPACE(c)) {
		    /* ignore backslashed spaces in %w */
		}
		else if (c != term && !(paren && c == paren)) {
		    tokadd('\\');
		}
	    }
	}
	else if (ismbchar(c)) {
	    int i, len = mbclen(c)-1;

	    for (i = 0; i < len; i++) {
		tokadd(c);
		c = nextc();
	    }
	}
	else if ((func & STR_FUNC_QWORDS) && ISSPACE(c)) {
	    pushback(c);
	    break;
	}
	tokadd(c);
    }
    return c;
}