+ public static final Object NO_ARG = new Object();
+
+ class ByteCode extends Expr {
+
+ // This class interprets a small forthlike bytecode language
+ // we use to represent JavaScript. It's a stack machine.
+
+ // Each instruction is an opcode and a literal. Any operation
+ // that accesses the top of the stack and does not have a
+ // mandatory literal can be performed on a literal instead of
+ // the top of the stack.
+
+ // opcodes:
+ public static final byte arithmetic = -1; // -- arithmetic operators from parser
+ public static final byte LITERAL = -2; // < String | Number | null > -- push a literal onto the stack
+ public static final byte ARRAY = -3; // < size > -- create a new array of size <size>
+ public static final byte OBJECT = -4; // -- push an empty object onto the stack
+ public static final byte FUNCTION = -5; // < bytecode_block > -- push a new instance of a function with the given bytecode
+ public static final byte DECLARE = -6; // < name > -- declare <name> in the current scope
+ public static final byte THIS = -7; // -- push the topmost non-transparent scope onto the stack
+ public static final byte GET = -8; // -- get stack[0] from stack[1]
+ public static final byte PUT = -9; // -- put stack[1] to key stack[0] on stack[2]; leaves object on the stack
+ public static final byte THROW = -10; // -- throw topmost element
+ public static final byte RETURN = -11; // -- return the topmost value on the stack
+ public static final byte ASSERT = -12; // -- fail if topmost element is not true
+ public static final byte JT = -13; // < relative_address > -- pop the stack; if true, jump to <relative_address>
+ public static final byte JF = -21; // < relative_address > -- pop the stack; if false, jump to <relative_address>
+ public static final byte JMP = -22; // < relative_address > -- jump to <relative_address>
+ static public final byte POP = -14; // -- discard the top element on the stack
+
+ public static final byte CALL = -15; // < numargs > -- call stack[0] with the topmost <numargs> values as arguments
+ public static final byte TRY = -16; // < bytecode_block > -- run the block pointed to; returns with thrown exn on top of stack
+
+ public static final byte INSTANCEOF = -17; // -- ??
+ public static final byte TYPEOF = -18; // --
+
+ public static final byte FOR__IN = -19; // -- ??
+ public static final byte EXPR = -20; // -- transitional
+ public static final byte SWAP = -23; // -- transitional
+ public static final byte SCOPE = -30; // -- transitional
+
+ int[] op = new int[10];
+ Object[] arg = new Object[10];
+ int size = 0;
+
+ public ByteCode(int line) { super(line, "foo"); }
+ public ByteCode(int line, int op_, Object arg_) { this(line); add(op_, arg_); }
+
+ public int size() { return size; }
+ public void set(int pos, int op_, Object arg_) { op[pos] = op_; arg[pos] = arg_; }
+ public ByteCode add(int op_, Object arg_) {
+ if (size == op.length - 1) {
+ int[] op2 = new int[op.length * 2]; System.arraycopy(op, 0, op2, 0, op.length); op = op2;
+ Object[] arg2 = new Object[op.length * 2]; System.arraycopy(arg, 0, arg2, 0, arg.length); arg = arg2;
+ }
+ op[size] = op_;
+ arg[size] = arg_;
+ size++;
+ return this;
+ }
+
+ public Object eval(final JS.Scope s) throws ControlTransferException, JS.Exn {
+ return eval(s, new Parser.Thread());
+ }
+ public Object eval(JS.Scope s, Parser.Thread t) throws ControlTransferException {
+ for(int i=0; i<size; i++)
+ switch(op[i]) {
+ case arithmetic: break;
+ case LITERAL:
+ t.push(arg[i]);
+ break;
+ case OBJECT: t.push(new JS.Obj()); break;
+ case ARRAY: t.push(new JS.Array(toNumber(arg[i]).intValue())); break;
+ case DECLARE: s.declare(arg[i] == NO_ARG ? (String)t.pop() : (String)arg[i]); break;
+ case THIS: t.push(s); break; // FIXME: transparents
+ case ASSERT: if (!toBoolean(t.pop())) throw new EvaluatorException("assertion failed"); break;
+ case THROW: throw new JS.Exn(t.pop());
+ case JT: if (toBoolean(t.pop())) i += toNumber(arg[i]).intValue() - 1; break;
+ case JF: if (!toBoolean(t.pop())) i += toNumber(arg[i]).intValue() - 1; break;
+ case JMP: i += toNumber(arg[i]).intValue() - 1; break;
+ case POP: t.pop(); break;
+ case SWAP: t.swap(); break;
+
+ case PUT: {
+ Object val = arg[i] == NO_ARG ? t.pop() : arg[i];
+ Object key = t.pop();
+ ((JS)t.peek()).put(key, val);
+ t.push(val);
+ break;
+ }
+
+ case GET: {
+ Object v = arg[i] == NO_ARG ? t.pop() : arg[i];
+ Object o = t.pop();
+ t.push(doGet(o, v));
+ break;
+ }
+ case NOP: break;
+
+ case EXPR: t.push(((Expr)arg[i]).eval(s)); break;
+ case SCOPE: t.push(((Expr)arg[i]).eval(new JS.Scope(s))); break;
+
+ case CALL:
+ JS.Array arguments = new JS.Array();
+ int numArgs = toNumber(arg[i]).intValue();
+ arguments.setSize(numArgs);
+ for(int j=numArgs - 1; j >= 0; j--) arguments.setElementAt(t.pop(), j);
+ JS.Function f = (JS.Function)t.pop();
+ if (f == null) throw new JS.Exn(new EvaluatorException("attempted to call null"));
+ t.push(f.call(arguments));
+ break;
+
+ case FUNCTION: break;
+ case RETURN: break;
+ case TRY: break;
+ case INSTANCEOF: break;
+ case TYPEOF: break;
+ case FOR__IN: break;
+
+ case Lexer.BITNOT: t.push(new Long(~toLong(t.pop()))); break;
+ case Lexer.BANG: t.push(new Boolean(!toBoolean(t.pop()))); break;
+
+ case Lexer.INC: case Lexer.DEC: {
+ boolean isPrefix = toBoolean(arg[i]);
+ Object key = t.pop();
+ JS obj = (JS)t.pop();
+ Number num = toNumber(obj.get(key));
+ Number val = new Double(op[i] == Lexer.INC ? num.doubleValue() + 1.0 : num.doubleValue() - 1.0);
+ obj.put(key, val);
+ t.push(isPrefix ? val : num);
+ break;
+ }
+
+ default: {
+ Object right = t.pop();
+ Object left = t.pop();
+ switch(op[i]) {
+
+ case Lexer.BITOR: t.push(new Long(toLong(left) | toLong(right))); break;
+ case Lexer.BITXOR: t.push(new Long(toLong(left) ^ toLong(right))); break;
+ case Lexer.BITAND: t.push(new Long(toLong(left) & toLong(right))); break;
+
+ case Lexer.ADD: {
+ Object l = left;
+ Object r = right;
+ if (l instanceof String || r instanceof String) {
+ if (l == null) l = "null";
+ if (r == null) r = "null";
+ if (l instanceof Number && ((Number)l).doubleValue() == ((Number)l).longValue())
+ l = new Long(((Number)l).longValue());
+ if (r instanceof Number && ((Number)r).doubleValue() == ((Number)r).longValue())
+ r = new Long(((Number)r).longValue());
+ t.push(l.toString() + r.toString()); break;
+ }
+ t.push(new Double(toDouble(l) + toDouble(r))); break;
+ }
+
+ case Lexer.SUB: t.push(new Double(toDouble(left) - toDouble(right))); break;
+ case Lexer.MUL: t.push(new Double(toDouble(left) * toDouble(right))); break;
+ case Lexer.DIV: t.push(new Double(toDouble(left) / toDouble(right))); break;
+ case Lexer.MOD: t.push(new Double(toDouble(left) % toDouble(right))); break;
+
+ case Lexer.LSH: t.push(new Long(toLong(left) << toLong(right))); break;
+ case Lexer.RSH: t.push(new Long(toLong(left) >> toLong(right))); break;
+ case Lexer.URSH: t.push(new Long(toLong(left) >>> toLong(right))); break;
+
+ // FIXME: these need to work on strings
+ case Lexer.LT: t.push(toDouble(left) < toDouble(right) ? Boolean.TRUE : Boolean.FALSE); break;
+ case Lexer.LE: t.push(toDouble(left) <= toDouble(right) ? Boolean.TRUE : Boolean.FALSE); break;
+ case Lexer.GT: t.push(toDouble(left) > toDouble(right) ? Boolean.TRUE : Boolean.FALSE); break;
+ case Lexer.GE: t.push(toDouble(left) >= toDouble(right) ? Boolean.TRUE : Boolean.FALSE); break;
+
+ case Lexer.EQ:
+ case Lexer.NE: {
+ // FIXME: should use Javascript coercion-equality rules
+ Object l = left;
+ Object r = right;
+ boolean ret;
+ if (l == null) { Object tmp = r; r = l; l = tmp; }
+ if (l == null && r == null) ret = true;
+ else if (l instanceof Boolean) ret = new Boolean(toBoolean(r)).equals(l);
+ else if (l instanceof Number) ret = toNumber(r).doubleValue() == toNumber(l).doubleValue();
+ else if (l instanceof String) ret = r != null && l.equals(r.toString());
+ else ret = l.equals(r);
+ t.push(new Boolean(op[i] == Lexer.EQ ? ret : !ret)); break;
+ }
+
+ default: throw new Error("unknown opcode " + op[i]);
+ } }
+ }
+ if (t.size() != 1) {
+ throw new EvaluatorException("eval() terminated with " + t.size() + " elements on the stack; one expected");
+ }
+ return t.pop();
+ }
+
+ public Object doGet(final Object o, final Object v) {
+ if (o == null) throw new EvaluatorException("tried to get property \"" + v + "\" from the null value");
+ if (o instanceof String) {
+ if (v.equals("length")) return new Integer(((String)o).length());
+ else if (v.equals("substring")) return new JS.Function() {
+ public Object _call(JS.Array args) {
+ if (args.length() == 1) return ((String)o).substring(toNumber(args.elementAt(0)).intValue());
+ else if (args.length() == 2) return ((String)o).substring(toNumber(args.elementAt(0)).intValue(),
+ toNumber(args.elementAt(1)).intValue());
+ else throw new Error("String.substring() can only take one or two arguments");
+ }
+ };
+ else if (v.equals("toLowerCase")) return new JS.Function() {
+ public Object _call(JS.Array args) {
+ return ((String)o).toLowerCase();
+ } };
+ else if (v.equals("toUpperCase")) return new JS.Function() {
+ public Object _call(JS.Array args) {
+ return ((String)o).toString().toUpperCase();
+ } };
+ else if (v.equals("charAt")) return new JS.Function() {
+ public Object _call(JS.Array args) {
+ return ((String)o).charAt(toNumber(args.elementAt(0)).intValue()) + "";
+ } };
+ else if (v.equals("lastIndexOf")) return new JS.Function() {
+ public Object _call(JS.Array args) {
+ if (args.length() != 1) return null;
+ return new Integer(((String)o).lastIndexOf(args.elementAt(0).toString()));
+ } };
+ else if (v.equals("indexOf")) return new JS.Function() {
+ public Object _call(JS.Array args) {
+ if (args.length() != 1) return null;
+ return new Integer(((String)o).indexOf(args.elementAt(0).toString()));
+ } };
+ throw new Error("Not Implemented: properties on String objects");
+ } else if (o instanceof Boolean) {
+ throw new Error("Not Implemented: properties on Boolean objects");
+ } else if (o instanceof Number) {
+ Log.log(this, "Not Implemented: properties on Number objects");
+ return null;
+ //throw new Error("Not Implemented: properties on Number objects");
+ } else if (o instanceof JS) {
+ return ((JS)o).get(v);
+ }
+ return null;
+ }
+ }
+
+ class Thread {
+ public Object[] os = new Object[256];
+ int size = 0;
+ public void push(Object o) { os[size++] = o; }
+ public Object pop() { return os[--size]; }
+ public Object peek() { return os[size - 1]; }
+ public void swap() { Object temp = os[size - 1]; os[size - 1] = os[size - 2]; os[size - 2] = temp; }
+ public int size() { return size; }
+ }
+