1 // Copyright 2003 Adam Megacz, see the COPYING file for licensing [GPL]
10 * The public API for the JS engine. JS itself is actually a class
11 * implementing the absolute minimal amount of functionality for an
12 * Object which can be manipulated by JavaScript code. The static
13 * methods, fields, and inner classes of JS define the publicly
14 * visible API for the XWT JavaScript engine; code outside this
15 * package should never depend on anything not defined in this file.
17 public abstract class JS {
19 // Public Helper Methods //////////////////////////////////////////////////////////////////////
21 /** parse and compile a function */
22 public static Function parse(String sourceName, int firstLine, Reader sourceCode) throws IOException {
23 return new Function(sourceName, firstLine, sourceCode, null);
26 /** coerce an object to a Boolean */
27 public static boolean toBoolean(Object o) {
28 if (o == null) return false;
29 if (o instanceof Boolean) return ((Boolean)o).booleanValue();
30 if (o instanceof Long) return ((Long)o).longValue() != 0;
31 if (o instanceof Integer) return ((Integer)o).intValue() != 0;
32 if (o instanceof Number) {
33 double d = ((Number) o).doubleValue();
34 // NOTE: d == d is a test for NaN. It should be faster than Double.isNaN()
35 return d != 0.0 && d == d;
37 if (o instanceof String) return ((String)o).length() != 0;
41 /** coerce an object to a Long */
42 public static long toLong(Object o) { return toNumber(o).longValue(); }
44 /** coerce an object to an Int */
45 public static int toInt(Object o) { return toNumber(o).intValue(); }
47 /** coerce an object to a Double */
48 public static double toDouble(Object o) { return toNumber(o).doubleValue(); }
50 /** coerce an object to a Number */
51 public static Number toNumber(Object o) {
52 if (o == null) return new Long(0);
53 if (o instanceof Number) return ((Number)o);
55 // NOTE: There are about 3 pages of rules in ecma262 about string to number conversions
56 // We aren't even close to following all those rules. We probably never will be.
57 if (o instanceof String)
58 try { return new Double((String)o); } catch (NumberFormatException e) { return new Double(Double.NaN); }
59 if (o instanceof Boolean) return ((Boolean)o).booleanValue() ? new Long(1) : new Long(0);
60 if (o instanceof JS) return ((JS)o).coerceToNumber();
61 throw new Error("toNumber() got object of type " + o.getClass().getName() + " which we don't know how to handle");
64 /** coerce an object to a String */
65 public static String toString(Object o) {
66 if(o == null) return "null";
67 if(o instanceof String) return (String) o;
68 if(o instanceof Integer || o instanceof Long || o instanceof Boolean) return o.toString();
69 if(o instanceof JS) return ((JS)o).coerceToString();
70 if(o instanceof Double || o instanceof Float) {
71 double d = ((Number)o).doubleValue();
72 if((int)d == d) return Integer.toString((int)d);
78 // Instance Methods ////////////////////////////////////////////////////////////////////
80 public abstract Object get(Object key) throws JS.Exn;
81 public abstract Object put(Object key, Object val) throws JS.Exn;
82 public abstract Object[] keys();
83 public Object callMethod(Object method, Array args, boolean checkOnly) throws JS.Exn {
84 if (checkOnly) return Boolean.FALSE;
85 Object o = get(method);
86 if (o instanceof JS.Callable) return ((JS.Callable)o).call(args);
87 else if (o == null) throw new JS.Exn("Attempted to call non-existent method: " + method);
88 else throw new JS.Exn("Attempted to call a non-function: " +method);
91 public Number coerceToNumber() { throw new JS.Exn("tried to coerce a JavaScript object to a Number"); }
92 public String coerceToString() { throw new JS.Exn("tried to coerce a JavaScript object to a String"); }
93 public boolean coerceToBoolean() { throw new JS.Exn("tried to coerce a JavaScript object to a Boolean"); }
94 public String typeName() { return "object"; }
97 // Inner Classes /////////////////////////////////////////////////////////////////////////
99 /** A sensible implementation of the abstract methods in the JS class */
100 public static class Obj extends JS {
101 private Hash entries = null;
102 private boolean sealed = false;
103 public Obj() { this(false); }
104 public Obj(boolean sealed) { this.sealed = sealed; }
105 public void setSeal(boolean sealed) { this.sealed = sealed; } ///< a sealed object cannot have its properties modified
106 public Object put(Object key, Object val) { put2(key, null, val); return null; }
107 protected void put2(Object key, Object key2, Object val) {
109 if (entries == null) entries = new Hash();
110 entries.put(key, key2, val); }
111 public Object[] keys() { return entries == null ? new Object[0] : entries.keys(); }
112 public Object get(Object key) { return get(key, null); }
113 protected Object get(Object key, Object key2) {
114 if (entries == null) return null;
115 if(key2 == null && callMethod((String)key, null, true) == Boolean.TRUE)
116 return new Internal.CallableStub(this, key);
117 return entries.get(key, key2);
121 /** An exception which can be thrown and caught by JavaScript code */
122 public static class Exn extends RuntimeException {
123 private Object js = null;
124 public Exn(Object js) { this.js = js; }
125 public String toString() { return "JS.Exn: " + js; }
126 public String getMessage() { return toString(); }
127 public Object getObject() { return js; }
130 /** The publicly-visible face of JavaScript Array objects */
131 public static class Array extends ArrayImpl {
133 public Array(int size) { super(size); }
134 public void setSize(int i) { super.setSize(i); }
135 public int length() { return super.length(); }
136 public Object elementAt(int i) { return super.elementAt(i); }
137 public void addElement(Object o) { super.addElement(o); }
138 public void setElementAt(Object o, int i) { super.setElementAt(o, i); }
139 public Object get(Object key) { return super._get(key); }
140 public Object put(Object key, Object val) { super._put(key, val); return null; }
143 /** Any object which becomes part of the scope chain must support this interface */
144 public static class Scope extends ScopeImpl {
145 public Scope(Scope parentScope) { this(parentScope, false); }
146 public Scope(Scope parentScope, boolean sealed) { super(parentScope, sealed); }
147 public boolean isTransparent() { return super.isTransparent(); } //< transparent scopes are not returned by THIS
148 public boolean has(Object key) { return super.has(key); }
149 public Object get(Object key) { return super._get(key); }
150 public Object put(Object key, Object val) { super._put(key, val); return null; }
151 public void declare(String s) { super.declare(s); }
154 /** the result of a graft */
155 public static class Graft extends JS {
157 private Object replaced_key;
158 private Object replaced_val;
159 public Graft(JS graftee, Object key, Object val) {
160 if (graftee instanceof Array) throw new JS.Exn("can't graft onto Arrays (yet)");
161 if (graftee instanceof Callable) throw new JS.Exn("can't graft onto Callables (yet)");
162 if (graftee instanceof Scope) throw new JS.Exn("can't graft onto Scopes (yet)");
163 this.graftee = graftee;
167 public boolean equals(Object o) { return (this == o || graftee.equals(o)); }
168 public int hashCode() { return graftee.hashCode(); }
169 public Object get(Object key) { return replaced_key.equals(key) ? replaced_val : graftee.get(key); }
170 public Object put(Object key, Object val) { graftee.put(key, val); return null; }
171 public Object callMethod(Object method, Array args, boolean checkOnly) throws JS.Exn {
172 if (!replaced_key.equals(method)) return graftee.callMethod(method, args, checkOnly);
173 if (replaced_val instanceof Callable) return checkOnly ? Boolean.TRUE : ((Callable)replaced_val).call(args);
174 if (checkOnly) return Boolean.FALSE;
175 throw new JS.Exn("attempt to call non-function");
177 public Number coerceToNumber() { return graftee.coerceToNumber(); }
178 public String coerceToString() { return graftee.coerceToString(); }
179 public boolean coerceToBoolean() { return graftee.coerceToBoolean(); }
180 public String typeName() { return graftee.typeName(); }
181 public Object[] keys() {
182 Object[] ret = graftee.keys();
183 for(int i=0; i<ret.length; i++) if (replaced_key.equals(ret[i])) return ret;
184 Object[] ret2 = new Object[ret.length + 1];
185 System.arraycopy(ret, 0, ret2, 0, ret.length);
186 ret2[ret2.length - 1] = replaced_key;
191 /** anything that is callable with the () operator and wasn't compiled from JS code */
192 public static abstract class Callable extends JS.Obj {
193 public abstract Object call(JS.Array args) throws JS.Exn;
196 /** a scope that is populated with js objects and functions normally found in the global scope */
197 public static class GlobalScope extends GlobalScopeImpl {
198 public GlobalScope() { this(null); }
199 public GlobalScope(JS.Scope parent) { super(parent); }
202 public static class TailCall {
203 Function func = null;
204 JS.Array args = null;
205 public TailCall() { }
206 public TailCall set(Function func) { this.func = func; this.args = new JS.Array(); return this; }
207 public TailCall set(Function func, JS.Array args) { this.func = func; this.args = args; return this; }
210 /** encapsulates the state of a JavaScript "thread" (ie stack) */
211 public static class Context {
214 // Statics //////////////////////////////////////////////////////////////////////
217 * Return this from call/get/put in order to make the interpreter pause. The interpreter will expect a value
218 * (the return from the call or the get) to be pushed onto the stack when it is resumed.
220 public static Object pause = new Object();
222 private int getLine_() { return current().f == null ? -1 : (pc < 0 || pc >= f.size) ? -1 : f.line[pc]; }
223 public static int getLine() { return current().getLine_(); }
224 public static String getSourceName() { return current().f == null ? null : current().f.sourceName; }
226 /** fetches the currently-executing javascript function */
227 public static JS.Context current() { return (JS.Context)threadToContext.get(Thread.currentThread()); }
228 private static Hashtable threadToContext = new Hashtable();
231 // Instance members and methods //////////////////////////////////////////////////////////////////////
233 /** the currently-executing Function */
236 /** the currently-executing scope */
237 public Scope scope = null; // FIXME: do we really need this? the function should contain this info
239 /** the object stack */
240 Vec stack = new Vec();
242 /** the program counter */
245 public Context(Function function, Scope scope) {
246 if (scope == null) scope = new Scope(function.parentScope);
247 stack.push(new Function.CallMarker(this));
248 stack.push(new JS.Array());
253 public Object resume() { return resume(null); }
254 public Object resume(Object o) {
255 Thread t = Thread.currentThread();
256 Context old = (Context)threadToContext.get(t);
258 threadToContext.put(t, this);
260 return Function.eval(this);
262 if (old == null) threadToContext.remove(t);
263 else threadToContext.put(t, old);