1 // Copyright 2003 Adam Megacz, see the COPYING file for licensing [GPL]
8 * Parses a stream of lexed tokens into a tree of JSFunction's.
10 * There are three kinds of things we parse: blocks, statements, and
13 * - Expressions are a special type of statement that evaluates to a
14 * value (for example, "break" is not an expression, * but "3+2"
15 * is). Some tokens sequences start expressions (for * example,
16 * literal numbers) and others continue an expression which * has
17 * already been begun (for example, '+'). Finally, some *
18 * expressions are valid targets for an assignment operation; after
19 * * each of these expressions, continueExprAfterAssignable() is
20 * called * to check for an assignment operation.
22 * - A statement ends with a semicolon and does not return a value.
24 * - A block is a single statement or a sequence of statements
25 * surrounded by curly braces.
27 * Each parsing method saves the parserLine before doing its actual
28 * work and restores it afterwards. This ensures that parsing a
29 * subexpression does not modify the line number until a token
30 * *after* the subexpression has been consumed by the parent
33 * Technically it would be a better design for this class to build an
34 * intermediate parse tree and use that to emit bytecode. Here's the
37 * Advantages of building a parse tree:
38 * - easier to apply optimizations
39 * - would let us handle more sophisticated languages than JavaScript
41 * Advantages of leaving out the parse tree
42 * - faster compilation
43 * - less load on the garbage collector
44 * - much simpler code, easier to understand
47 * Fortunately JS is such a simple language that we can get away with
48 * the half-assed approach and still produce a working, complete
51 * The bytecode language emitted doesn't really cause any appreciable
52 * semantic loss, and is itself a parseable language very similar to
53 * Forth or a postfix variant of LISP. This means that the bytecode
54 * can be transformed into a parse tree, which can be manipulated.
55 * So if we ever want to add an optimizer, it could easily be done by
56 * producing a parse tree from the bytecode, optimizing that tree,
57 * and then re-emitting the bytecode. The parse tree node class
58 * would also be much simpler since the bytecode language has so few
61 * Actually, the above paragraph is slightly inaccurate -- there are
62 * places where we push a value and then perform an arbitrary number
63 * of operations using it before popping it; this doesn't parse well.
64 * But these cases are clearly marked and easy to change if we do
65 * need to move to a parse tree format.
67 class Parser extends Lexer implements ByteCodes {
70 // Constructors //////////////////////////////////////////////////////
72 public Parser(Reader r, String sourceName, int line) throws IOException { super(r, sourceName, line); }
75 public static void main(String[] s) throws Exception {
76 JSFunction block = JSFunction.fromReader("stdin", 0, new InputStreamReader(System.in));
77 if (block == null) return;
78 System.out.println(block);
82 // Statics ////////////////////////////////////////////////////////////
84 static byte[] precedence = new byte[MAX_TOKEN + 1];
85 static boolean[] isRightAssociative = new boolean[MAX_TOKEN + 1];
86 // Use this as the precedence when we want anything up to the comma
87 private final static int NO_COMMA = 2;
89 isRightAssociative[ASSIGN] =
90 isRightAssociative[ASSIGN_BITOR] =
91 isRightAssociative[ASSIGN_BITXOR] =
92 isRightAssociative[ASSIGN_BITAND] =
93 isRightAssociative[ASSIGN_LSH] =
94 isRightAssociative[ASSIGN_RSH] =
95 isRightAssociative[ASSIGN_URSH] =
96 isRightAssociative[ASSIGN_ADD] =
97 isRightAssociative[ASSIGN_SUB] =
98 isRightAssociative[ASSIGN_MUL] =
99 isRightAssociative[ASSIGN_DIV] =
100 isRightAssociative[ASSIGN_MOD] = true;
102 precedence[COMMA] = 1;
103 // 2 is intentionally left unassigned. we use minPrecedence==2 for comma separated lists
105 precedence[ASSIGN_BITOR] =
106 precedence[ASSIGN_BITXOR] =
107 precedence[ASSIGN_BITAND] =
108 precedence[ASSIGN_LSH] =
109 precedence[ASSIGN_RSH] =
110 precedence[ASSIGN_URSH] =
111 precedence[ASSIGN_ADD] =
112 precedence[ASSIGN_SUB] =
113 precedence[ASSIGN_MUL] =
114 precedence[ASSIGN_DIV] =
115 precedence[ASSIGN_MOD] = 3;
116 precedence[HOOK] = 4;
119 precedence[BITOR] = 7;
120 precedence[BITXOR] = 8;
121 precedence[BITAND] = 9;
122 precedence[EQ] = precedence[NE] = precedence[SHEQ] = precedence[SHNE] = 10;
123 precedence[LT] = precedence[LE] = precedence[GT] = precedence[GE] = 11;
124 precedence[LSH] = precedence[RSH] = precedence[URSH] = 12;
125 precedence[ADD] = precedence[SUB] = 12;
126 precedence[MUL] = precedence[DIV] = precedence[MOD] = 13;
127 precedence[BITNOT] = precedence[BANG] = precedence[TYPEOF] = 14;
128 precedence[DOT] = precedence[LB] = precedence[LP] = precedence[INC] = precedence[DEC] = 15;
132 // Parsing Logic /////////////////////////////////////////////////////////
134 /** gets a token and throws an exception if it is not <tt>code</tt> */
135 private void consume(int code) throws IOException {
136 if (getToken() != code) {
137 if(code == NAME) switch(op) {
138 case RETURN: case TYPEOF: case BREAK: case CONTINUE: case TRY: case THROW:
139 case ASSERT: case NULL: case TRUE: case FALSE: case IN: case IF: case ELSE:
140 case SWITCH: case CASE: case DEFAULT: case WHILE: case VAR: case WITH:
141 case CATCH: case FINALLY:
142 throw pe("Bad variable name; '" + codeToString[op].toLowerCase() + "' is a javascript keyword");
144 throw pe("expected " + codeToString[code] + ", got " + (op == -1 ? "EOF" : codeToString[op]));
149 * Parse the largest possible expression containing no operators
150 * of precedence below <tt>minPrecedence</tt> and append the
151 * bytecodes for that expression to <tt>appendTo</tt>; the
152 * appended bytecodes MUST grow the stack by exactly one element.
154 private void startExpr(JSFunction appendTo, int minPrecedence) throws IOException {
155 int saveParserLine = parserLine;
156 _startExpr(appendTo, minPrecedence);
157 parserLine = saveParserLine;
159 private void _startExpr(JSFunction appendTo, int minPrecedence) throws IOException {
160 int tok = getToken();
161 JSFunction b = appendTo;
164 case -1: throw pe("expected expression");
166 // all of these simply push values onto the stack
167 case NUMBER: b.add(parserLine, LITERAL, number); break;
168 case STRING: b.add(parserLine, LITERAL, string); break;
169 case NULL: b.add(parserLine, LITERAL, null); break;
170 case TRUE: case FALSE: b.add(parserLine, LITERAL, JS.B(tok == TRUE)); break;
175 b.add(parserLine, TOPSCOPE);
176 b.add(parserLine, LITERAL, "");
177 b.add(parserLine, GET);
178 b.add(parserLine, LITERAL, string);
179 b.add(parserLine, GET);
180 continueExpr(b, minPrecedence);
185 b.add(parserLine, ARRAY, JS.ZERO); // push an array onto the stack
188 if (peekToken() != RB)
189 while(true) { // iterate over the initialization values
191 b.add(parserLine, LITERAL, JS.N(i++)); // push the index in the array to place it into
192 if (peekToken() == COMMA || peekToken() == RB)
193 b.add(parserLine, LITERAL, null); // for stuff like [1,,2,]
195 startExpr(b, NO_COMMA); // push the value onto the stack
196 b.add(parserLine, PUT); // put it into the array
197 b.add(parserLine, POP); // discard the value remaining on the stack
198 if (peekToken() == RB) break;
201 b.set(size0 - 1, JS.N(i)); // back at the ARRAY instruction, write the size of the array
205 case SUB: { // negative literal (like "3 * -1")
207 b.add(parserLine, LITERAL, JS.N(number.doubleValue() * -1));
210 case LP: { // grouping (not calling)
215 case INC: case DEC: { // prefix (not postfix)
216 startExpr(b, precedence[tok]);
217 int prev = b.size - 1;
218 if (b.get(prev) == GET && b.getArg(prev) != null)
219 b.set(prev, LITERAL, b.getArg(prev));
220 else if(b.get(prev) == GET)
223 throw pe("prefixed increment/decrement can only be performed on a valid assignment target");
224 b.add(parserLine, GET_PRESERVE, Boolean.TRUE);
225 b.add(parserLine, LITERAL, JS.N(1));
226 b.add(parserLine, tok == INC ? ADD : SUB, JS.N(2));
227 b.add(parserLine, PUT, null);
228 b.add(parserLine, SWAP, null);
229 b.add(parserLine, POP, null);
232 case BANG: case BITNOT: case TYPEOF: {
233 startExpr(b, precedence[tok]);
234 b.add(parserLine, tok);
237 case LC: { // object constructor
238 b.add(parserLine, OBJECT, null); // put an object on the stack
239 if (peekToken() != RC)
241 if (peekToken() != NAME && peekToken() != STRING)
242 throw pe("expected NAME or STRING");
244 b.add(parserLine, LITERAL, string); // grab the key
246 startExpr(b, NO_COMMA); // grab the value
247 b.add(parserLine, PUT); // put the value into the object
248 b.add(parserLine, POP); // discard the remaining value
249 if (peekToken() == RC) break;
251 if (peekToken() == RC) break; // we permit {,,} -- I'm not sure if ECMA does
257 b.add(parserLine, TOPSCOPE);
258 b.add(parserLine, LITERAL, string);
259 continueExprAfterAssignable(b,minPrecedence);
265 JSFunction b2 = new JSFunction(sourceName, parserLine, null);
266 b.add(parserLine, NEWFUNCTION, b2);
268 // function prelude; arguments array is already on the stack
269 b2.add(parserLine, TOPSCOPE);
270 b2.add(parserLine, SWAP);
271 b2.add(parserLine, DECLARE, "arguments"); // declare arguments (equivalent to 'var arguments;')
272 b2.add(parserLine, SWAP); // set this.arguments and leave the value on the stack
273 b2.add(parserLine, PUT);
275 while(peekToken() != RP) { // run through the list of argument names
277 if (peekToken() == NAME) {
278 consume(NAME); // a named argument
279 String varName = string;
281 b2.add(parserLine, DUP); // dup the args array
282 b2.add(parserLine, GET, JS.N(numArgs - 1)); // retrieve it from the arguments array
283 b2.add(parserLine, TOPSCOPE);
284 b2.add(parserLine, SWAP);
285 b2.add(parserLine, DECLARE, varName); // declare the name
286 b2.add(parserLine, SWAP);
287 b2.add(parserLine, PUT);
288 b2.add(parserLine, POP); // pop the value
289 b2.add(parserLine, POP); // pop the scope
291 if (peekToken() == RP) break;
296 b2.numFormalArgs = numArgs;
297 b2.add(parserLine, POP); // pop off the arguments array
298 b2.add(parserLine, POP); // pop off TOPSCOPE
300 if(peekToken() != LC)
301 throw pe("JSFunctions must have a block surrounded by curly brackets");
303 parseBlock(b2, null); // the function body
305 b2.add(parserLine, LITERAL, null); // in case we "fall out the bottom", return NULL
306 b2.add(parserLine, RETURN);
310 default: throw pe("expected expression, found " + codeToString[tok] + ", which cannot start an expression");
313 // attempt to continue the expression
314 continueExpr(b, minPrecedence);
319 * Assuming that a complete assignable (lvalue) has just been
320 * parsed and the object and key are on the stack,
321 * <tt>continueExprAfterAssignable</tt> will attempt to parse an
322 * expression that modifies the assignable. This method always
323 * decreases the stack depth by exactly one element.
325 private void continueExprAfterAssignable(JSFunction b,int minPrecedence) throws IOException {
326 int saveParserLine = parserLine;
327 _continueExprAfterAssignable(b,minPrecedence);
328 parserLine = saveParserLine;
330 private void _continueExprAfterAssignable(JSFunction b,int minPrecedence) throws IOException {
331 if (b == null) throw new Error("got null b; this should never happen");
332 int tok = getToken();
333 if (minPrecedence != -1 && (precedence[tok] < minPrecedence || (precedence[tok] == minPrecedence && !isRightAssociative[tok])))
334 // force the default case
337 case ASSIGN_BITOR: case ASSIGN_BITXOR: case ASSIGN_BITAND: case ASSIGN_LSH: case ASSIGN_RSH: case ASSIGN_URSH:
338 case ASSIGN_MUL: case ASSIGN_DIV: case ASSIGN_MOD: case ASSIGN_ADD: case ASSIGN_SUB: {
339 if (tok != ASSIGN_ADD && tok != ASSIGN_SUB) b.add(parserLine, GET_PRESERVE);
341 startExpr(b, precedence[tok]);
344 if (tok == ASSIGN_ADD || tok == ASSIGN_SUB) {
345 b.add(parserLine, tok);
346 b.add(parserLine, GET);
347 b.add(parserLine, SWAP);
350 // tok-1 is always s/^ASSIGN_// (0 is BITOR, 1 is ASSIGN_BITOR, etc)
351 b.add(parserLine, tok - 1, tok-1==ADD ? JS.N(2) : null);
352 b.add(parserLine, PUT);
353 b.add(parserLine, SWAP);
354 b.add(parserLine, POP);
356 if (tok == ASSIGN_ADD || tok == ASSIGN_SUB) b.set(size, tok, JS.N(b.size - size));
359 case INC: case DEC: { // postfix
360 b.add(parserLine, GET_PRESERVE, Boolean.TRUE);
361 b.add(parserLine, LITERAL, JS.N(1));
362 b.add(parserLine, tok == INC ? ADD : SUB, JS.N(2));
363 b.add(parserLine, PUT, null);
364 b.add(parserLine, SWAP, null);
365 b.add(parserLine, POP, null);
366 b.add(parserLine, LITERAL, JS.N(1));
367 b.add(parserLine, tok == INC ? SUB : ADD, null); // undo what we just did, since this is postfix
371 startExpr(b, precedence[tok]);
372 b.add(parserLine, PUT);
373 b.add(parserLine, SWAP);
374 b.add(parserLine, POP);
379 // Method calls are implemented by doing a GET_PRESERVE
380 // first. If the object supports method calls, it will
382 int n = parseArgs(b, 2);
383 b.add(parserLine, GET_PRESERVE);
384 b.add(parserLine, CALLMETHOD, JS.N(n));
389 if(b.get(b.size-1) == LITERAL && b.getArg(b.size-1) != null)
390 b.set(b.size-1,GET,b.getArg(b.size-1));
392 b.add(parserLine, GET);
400 * Assuming that a complete expression has just been parsed,
401 * <tt>continueExpr</tt> will attempt to extend this expression by
402 * parsing additional tokens and appending additional bytecodes.
404 * No operators with precedence less than <tt>minPrecedence</tt>
407 * If any bytecodes are appended, they will not alter the stack
410 private void continueExpr(JSFunction b, int minPrecedence) throws IOException {
411 int saveParserLine = parserLine;
412 _continueExpr(b, minPrecedence);
413 parserLine = saveParserLine;
415 private void _continueExpr(JSFunction b, int minPrecedence) throws IOException {
416 if (b == null) throw new Error("got null b; this should never happen");
417 int tok = getToken();
418 if (tok == -1) return;
419 if (minPrecedence != -1 && (precedence[tok] < minPrecedence || (precedence[tok] == minPrecedence && !isRightAssociative[tok]))) {
425 case LP: { // invocation (not grouping)
426 int n = parseArgs(b, 1);
427 b.add(parserLine, CALL, JS.N(n));
430 case BITOR: case BITXOR: case BITAND: case SHEQ: case SHNE: case LSH:
431 case RSH: case URSH: case MUL: case DIV: case MOD:
432 case GT: case GE: case EQ: case NE: case LT: case LE: case SUB: {
433 startExpr(b, precedence[tok]);
434 b.add(parserLine, tok);
441 startExpr(b,precedence[tok]);
443 nextTok = getToken();
444 } while(nextTok == tok);
446 b.add(parserLine, tok, JS.N(count));
450 b.add(parserLine, tok == AND ? b.JF : b.JT, JS.ZERO); // test to see if we can short-circuit
452 startExpr(b, precedence[tok]); // otherwise check the second value
453 b.add(parserLine, JMP, JS.N(2)); // leave the second value on the stack and jump to the end
454 b.add(parserLine, LITERAL, tok == AND ?
455 JS.B(false) : JS.B(true)); // target of the short-circuit jump is here
456 b.set(size - 1, JS.N(b.size - size)); // write the target of the short-circuit jump
460 // support foo..bar syntax for foo[""].bar
461 if (peekToken() == DOT) {
466 b.add(parserLine, LITERAL, string);
467 continueExprAfterAssignable(b,minPrecedence);
470 case LB: { // subscripting (not array constructor)
473 continueExprAfterAssignable(b,minPrecedence);
477 b.add(parserLine, JF, JS.ZERO); // jump to the if-false expression
479 startExpr(b, minPrecedence); // write the if-true expression
480 b.add(parserLine, JMP, JS.ZERO); // if true, jump *over* the if-false expression
481 b.set(size - 1, JS.N(b.size - size + 1)); // now we know where the target of the jump is
484 startExpr(b, minPrecedence); // write the if-false expression
485 b.set(size - 1, JS.N(b.size - size + 1)); // this is the end; jump to here
489 // pop the result of the previous expression, it is ignored
490 b.add(parserLine,POP);
500 continueExpr(b, minPrecedence); // try to continue the expression
503 // parse a set of comma separated function arguments, assume LP has already been consumed
504 // if swap is true, (because the function is already on the stack) we will SWAP after each argument to keep it on top
505 private int parseArgs(JSFunction b, int pushdown) throws IOException {
507 while(peekToken() != RP) {
509 if (peekToken() != COMMA) {
510 startExpr(b, NO_COMMA);
511 b.add(parserLine, SWAP, JS.N(pushdown));
512 if (peekToken() == RP) break;
520 /** Parse a block of statements which must be surrounded by LC..RC. */
521 void parseBlock(JSFunction b) throws IOException { parseBlock(b, null); }
522 void parseBlock(JSFunction b, String label) throws IOException {
523 int saveParserLine = parserLine;
524 _parseBlock(b, label);
525 parserLine = saveParserLine;
527 void _parseBlock(JSFunction b, String label) throws IOException {
528 if (peekToken() == -1) return;
529 else if (peekToken() != LC) parseStatement(b, null);
532 while(peekToken() != RC && peekToken() != -1) parseStatement(b, null);
537 /** Parse a single statement, consuming the RC or SEMI which terminates it. */
538 void parseStatement(JSFunction b, String label) throws IOException {
539 int saveParserLine = parserLine;
540 _parseStatement(b, label);
541 parserLine = saveParserLine;
543 void _parseStatement(JSFunction b, String label) throws IOException {
544 int tok = peekToken();
545 if (tok == -1) return;
546 switch(tok = getToken()) {
548 case THROW: case ASSERT: case RETURN: {
549 if (tok == RETURN && peekToken() == SEMI)
550 b.add(parserLine, LITERAL, null);
553 b.add(parserLine, tok);
557 case BREAK: case CONTINUE: {
558 if (peekToken() == NAME) consume(NAME);
559 b.add(parserLine, tok, string);
564 b.add(parserLine, TOPSCOPE); // push the current scope
567 b.add(parserLine, DECLARE, string); // declare it
568 if (peekToken() == ASSIGN) { // if there is an '=' after the variable name
570 startExpr(b, NO_COMMA);
571 b.add(parserLine, PUT); // assign it
572 b.add(parserLine, POP); // clean the stack
574 b.add(parserLine, POP); // pop the string pushed by declare
576 if (peekToken() != COMMA) break;
579 b.add(parserLine, POP); // pop off the topscope
580 if ((mostRecentlyReadToken != RC || peekToken() == SEMI) && peekToken() != -1 && mostRecentlyReadToken != SEMI) consume(SEMI);
588 b.add(parserLine, JF, JS.ZERO); // if false, jump to the else-block
590 parseStatement(b, null);
592 if (peekToken() == ELSE) {
594 b.add(parserLine, JMP, JS.ZERO); // if we took the true-block, jump over the else-block
595 b.set(size - 1, JS.N(b.size - size + 1));
597 parseStatement(b, null);
599 b.set(size - 1, JS.N(b.size - size + 1)); // regardless of which branch we took, b[size] needs to point here
604 if (label != null) b.add(parserLine, LABEL, label);
605 b.add(parserLine, LOOP);
607 b.add(parserLine, POP); // discard the first-iteration indicator
609 b.add(parserLine, JT, JS.N(2)); // if the while() clause is true, jump over the BREAK
610 b.add(parserLine, BREAK);
612 parseStatement(b, null);
613 b.add(parserLine, CONTINUE); // if we fall out of the end, definately continue
614 b.set(size - 1, JS.N(b.size - size + 1)); // end of the loop
619 if (label != null) b.add(parserLine, LABEL, label);
620 b.add(parserLine, LOOP);
626 if (peekToken() == CASE) { // we compile CASE statements like a bunch of if..else's
628 b.add(parserLine, DUP); // duplicate the switch() value; we'll consume one copy
631 b.add(parserLine, EQ); // check if we should do this case-block
632 b.add(parserLine, JF, JS.ZERO); // if not, jump to the next one
634 while(peekToken() != CASE && peekToken() != DEFAULT && peekToken() != RC) parseStatement(b, null);
635 b.set(size - 1, JS.N(1 + b.size - size));
636 } else if (peekToken() == DEFAULT) {
639 while(peekToken() != CASE && peekToken() != DEFAULT && peekToken() != RC) parseStatement(b, null);
640 } else if (peekToken() == RC) {
642 b.add(parserLine, BREAK); // break out of the loop if we 'fall through'
645 throw pe("expected CASE, DEFAULT, or RC; got " + codeToString[peekToken()]);
647 b.set(size0 - 1, JS.N(b.size - size0 + 1)); // end of the loop
652 if (label != null) b.add(parserLine, LABEL, label);
653 b.add(parserLine, LOOP);
655 parseStatement(b, null);
659 b.add(parserLine, JT, JS.N(2)); // check the while() clause; jump over the BREAK if true
660 b.add(parserLine, BREAK);
661 b.add(parserLine, CONTINUE);
664 b.set(size - 1, JS.N(b.size - size + 1)); // end of the loop; write this location to the LOOP instruction
669 b.add(parserLine, TRY); // try bytecode causes a TryMarker to be pushed
670 int tryInsn = b.size - 1;
671 // parse the expression to be TRYed
672 parseStatement(b, null);
673 // pop the try marker. this is pushed when the TRY bytecode is executed
674 b.add(parserLine, POP);
675 // jump forward to the end of the catch block, start of the finally block
676 b.add(parserLine, JMP);
677 int successJMPInsn = b.size - 1;
679 if (peekToken() != CATCH && peekToken() != FINALLY)
680 throw pe("try without catch or finally");
682 int catchJMPDistance = -1;
683 if (peekToken() == CATCH) {
684 catchJMPDistance = b.size - tryInsn;
689 exceptionVar = string;
691 b.add(parserLine, TOPSCOPE); // the exception is on top of the stack; put it to the chosen name
692 b.add(parserLine, SWAP);
693 b.add(parserLine, LITERAL,exceptionVar);
694 b.add(parserLine, SWAP);
695 b.add(parserLine, PUT);
696 b.add(parserLine, POP);
697 b.add(parserLine, POP);
698 parseStatement(b, null);
699 // pop the try and catch markers
700 b.add(parserLine,POP);
701 b.add(parserLine,POP);
704 // jump here if no exception was thrown
705 b.set(successJMPInsn, JS.N(b.size - successJMPInsn));
707 int finallyJMPDistance = -1;
708 if (peekToken() == FINALLY) {
709 b.add(parserLine, LITERAL, null); // null FinallyData
710 finallyJMPDistance = b.size - tryInsn;
712 parseStatement(b, null);
713 b.add(parserLine,FINALLY_DONE);
716 // setup the TRY arguments
717 b.set(tryInsn, new int[] { catchJMPDistance, finallyJMPDistance });
726 boolean hadVar = false; // if it's a for..in, we ignore the VAR
727 if (tok == VAR) { hadVar = true; tok = getToken(); }
728 String varName = string;
729 boolean forIn = peekToken() == IN; // determine if this is a for..in loop or not
730 pushBackToken(tok, varName);
733 b.add(parserLine, NEWSCOPE); // for-loops always create new scopes
734 b.add(parserLine, LITERAL, varName); // declare the new variable
735 b.add(parserLine, DECLARE);
737 b.add(parserLine, LOOP); // we actually only add this to ensure that BREAK works
738 b.add(parserLine, POP); // discard the first-iteration indicator
743 b.add(parserLine, PUSHKEYS); // push the keys as an array; check the length
744 b.add(parserLine, LITERAL, "length");
745 b.add(parserLine, GET);
748 b.add(parserLine, LITERAL, JS.N(1)); // decrement the length
749 b.add(parserLine, SUB);
750 b.add(parserLine, DUP);
751 b.add(parserLine, LITERAL, JS.ZERO); // see if we've exhausted all the elements
752 b.add(parserLine, LT);
753 b.add(parserLine, JF, JS.N(2));
754 b.add(parserLine, BREAK); // if we have, then BREAK
755 b.add(parserLine, GET_PRESERVE); // get the key out of the keys array
756 b.add(parserLine, LITERAL, varName);
757 b.add(parserLine, PUT); // write it to this[varName]
758 parseStatement(b, null); // do some stuff
759 b.add(parserLine, CONTINUE); // continue if we fall out the bottom
761 b.set(size - 1, JS.N(b.size - size + 1)); // BREAK to here
762 b.add(parserLine, OLDSCOPE); // restore the scope
765 if (hadVar) pushBackToken(VAR, null); // yeah, this actually matters
766 b.add(parserLine, NEWSCOPE); // grab a fresh scope
768 parseStatement(b, null); // initializer
769 JSFunction e2 = // we need to put the incrementor before the test
770 new JSFunction(sourceName, parserLine, null); // so we save the test here
771 if (peekToken() != SEMI)
774 e2.add(parserLine, b.LITERAL, Boolean.TRUE); // handle the for(foo;;foo) case
776 if (label != null) b.add(parserLine, LABEL, label);
777 b.add(parserLine, LOOP);
780 b.add(parserLine, JT, JS.ZERO); // if we're on the first iteration, jump over the incrementor
782 if (peekToken() != RP) { // do the increment thing
784 b.add(parserLine, POP);
786 b.set(size - 1, JS.N(b.size - size + 1));
789 b.paste(e2); // ok, *now* test if we're done yet
790 b.add(parserLine, JT, JS.N(2)); // break out if we don't meet the test
791 b.add(parserLine, BREAK);
792 parseStatement(b, null);
793 b.add(parserLine, CONTINUE); // if we fall out the bottom, CONTINUE
794 b.set(size2 - 1, JS.N(b.size - size2 + 1)); // end of the loop
796 b.add(parserLine, OLDSCOPE); // get our scope back
801 case NAME: { // either a label or an identifier; this is the one place we're not LL(1)
802 String possiblyTheLabel = string;
803 if (peekToken() == COLON) { // label
805 parseStatement(b, possiblyTheLabel);
807 } else { // expression
808 pushBackToken(NAME, possiblyTheLabel);
810 b.add(parserLine, POP);
811 if ((mostRecentlyReadToken != RC || peekToken() == SEMI) && peekToken() != -1 && mostRecentlyReadToken != SEMI) consume(SEMI);
816 case SEMI: return; // yep, the null statement is valid
818 case LC: { // blocks are statements too
820 b.add(parserLine, NEWSCOPE);
821 parseBlock(b, label);
822 b.add(parserLine, OLDSCOPE);
826 default: { // hope that it's an expression
829 b.add(parserLine, POP);
830 if ((mostRecentlyReadToken != RC || peekToken() == SEMI) && peekToken() != -1 && mostRecentlyReadToken != SEMI) consume(SEMI);
837 // ParserException //////////////////////////////////////////////////////////////////////
838 private IOException pe(String s) { return new IOException(sourceName + ":" + parserLine + " " + s); }