handles.h revision 8defd9ff6930b4e24729971a61cf7469daf119be 
1// Copyright 2006-2008 the V8 project authors. All rights reserved.
2// Redistribution and use in source and binary forms, with or without
3// modification, are permitted provided that the following conditions are
4// met:
5//
6//     * Redistributions of source code must retain the above copyright
7//       notice, this list of conditions and the following disclaimer.
8//     * Redistributions in binary form must reproduce the above
9//       copyright notice, this list of conditions and the following
10//       disclaimer in the documentation and/or other materials provided
11//       with the distribution.
12//     * Neither the name of Google Inc. nor the names of its
13//       contributors may be used to endorse or promote products derived
14//       from this software without specific prior written permission.
15//
16// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
28#ifndef V8_HANDLES_H_
29#define V8_HANDLES_H_
30
31#include "apiutils.h"
32
33namespace v8 {
34namespace internal {
35
36// ----------------------------------------------------------------------------
37// A Handle provides a reference to an object that survives relocation by
38// the garbage collector.
39// Handles are only valid within a HandleScope.
40// When a handle is created for an object a cell is allocated in the heap.
41
42template<class T>
43class Handle {
44 public:
45  INLINE(explicit Handle(T** location)) { location_ = location; }
46  INLINE(explicit Handle(T* obj));
47
48  INLINE(Handle()) : location_(NULL) {}
49
50  // Constructor for handling automatic up casting.
51  // Ex. Handle<JSFunction> can be passed when Handle<Object> is expected.
52  template <class S> Handle(Handle<S> handle) {
53#ifdef DEBUG
54    T* a = NULL;
55    S* b = NULL;
56    a = b;  // Fake assignment to enforce type checks.
57    USE(a);
58#endif
59    location_ = reinterpret_cast<T**>(handle.location());
60  }
61
62  INLINE(T* operator ->() const) { return operator*(); }
63
64  // Check if this handle refers to the exact same object as the other handle.
65  bool is_identical_to(const Handle<T> other) const {
66    return operator*() == *other;
67  }
68
69  // Provides the C++ dereference operator.
70  INLINE(T* operator*() const);
71
72  // Returns the address to where the raw pointer is stored.
73  T** location() const {
74    ASSERT(location_ == NULL ||
75           reinterpret_cast<Address>(*location_) != kZapValue);
76    return location_;
77  }
78
79  template <class S> static Handle<T> cast(Handle<S> that) {
80    T::cast(*that);
81    return Handle<T>(reinterpret_cast<T**>(that.location()));
82  }
83
84  static Handle<T> null() { return Handle<T>(); }
85  bool is_null() { return location_ == NULL; }
86
87  // Closes the given scope, but lets this handle escape. See
88  // implementation in api.h.
89  inline Handle<T> EscapeFrom(v8::HandleScope* scope);
90
91 private:
92  T** location_;
93};
94
95
96// A stack-allocated class that governs a number of local handles.
97// After a handle scope has been created, all local handles will be
98// allocated within that handle scope until either the handle scope is
99// deleted or another handle scope is created.  If there is already a
100// handle scope and a new one is created, all allocations will take
101// place in the new handle scope until it is deleted.  After that,
102// new handles will again be allocated in the original handle scope.
103//
104// After the handle scope of a local handle has been deleted the
105// garbage collector will no longer track the object stored in the
106// handle and may deallocate it.  The behavior of accessing a handle
107// for which the handle scope has been deleted is undefined.
108class HandleScope {
109 public:
110  HandleScope() : previous_(current_) {
111    current_.extensions = 0;
112  }
113
114  ~HandleScope() {
115    Leave(&previous_);
116  }
117
118  // Counts the number of allocated handles.
119  static int NumberOfHandles();
120
121  // Creates a new handle with the given value.
122  template <typename T>
123  static inline T** CreateHandle(T* value) {
124    internal::Object** cur = current_.next;
125    if (cur == current_.limit) cur = Extend();
126    // Update the current next field, set the value in the created
127    // handle, and return the result.
128    ASSERT(cur < current_.limit);
129    current_.next = cur + 1;
130
131    T** result = reinterpret_cast<T**>(cur);
132    *result = value;
133    return result;
134  }
135
136  // Deallocates any extensions used by the current scope.
137  static void DeleteExtensions();
138
139  static Address current_extensions_address();
140  static Address current_next_address();
141  static Address current_limit_address();
142
143 private:
144  // Prevent heap allocation or illegal handle scopes.
145  HandleScope(const HandleScope&);
146  void operator=(const HandleScope&);
147  void* operator new(size_t size);
148  void operator delete(void* size_t);
149
150  static v8::ImplementationUtilities::HandleScopeData current_;
151  const v8::ImplementationUtilities::HandleScopeData previous_;
152
153  // Pushes a fresh handle scope to be used when allocating new handles.
154  static void Enter(
155      v8::ImplementationUtilities::HandleScopeData* previous) {
156    *previous = current_;
157    current_.extensions = 0;
158  }
159
160  // Re-establishes the previous scope state. Should be called only
161  // once, and only for the current scope.
162  static void Leave(
163      const v8::ImplementationUtilities::HandleScopeData* previous) {
164    if (current_.extensions > 0) {
165      DeleteExtensions();
166    }
167    current_ = *previous;
168#ifdef DEBUG
169    ZapRange(current_.next, current_.limit);
170#endif
171  }
172
173  // Extend the handle scope making room for more handles.
174  static internal::Object** Extend();
175
176  // Zaps the handles in the half-open interval [start, end).
177  static void ZapRange(internal::Object** start, internal::Object** end);
178
179  friend class v8::HandleScope;
180  friend class v8::ImplementationUtilities;
181};
182
183
184// ----------------------------------------------------------------------------
185// Handle operations.
186// They might invoke garbage collection. The result is an handle to
187// an object of expected type, or the handle is an error if running out
188// of space or encountering an internal error.
189
190void NormalizeProperties(Handle<JSObject> object,
191                         PropertyNormalizationMode mode,
192                         int expected_additional_properties);
193void NormalizeElements(Handle<JSObject> object);
194void TransformToFastProperties(Handle<JSObject> object,
195                               int unused_property_fields);
196
197// Flattens a string.
198void FlattenString(Handle<String> str);
199
200// Flattens a string and returns the underlying external or sequential
201// string.
202Handle<String> FlattenGetString(Handle<String> str);
203
204Handle<Object> SetProperty(Handle<JSObject> object,
205                           Handle<String> key,
206                           Handle<Object> value,
207                           PropertyAttributes attributes);
208
209Handle<Object> SetProperty(Handle<Object> object,
210                           Handle<Object> key,
211                           Handle<Object> value,
212                           PropertyAttributes attributes);
213
214Handle<Object> ForceSetProperty(Handle<JSObject> object,
215                                Handle<Object> key,
216                                Handle<Object> value,
217                                PropertyAttributes attributes);
218
219Handle<Object> SetNormalizedProperty(Handle<JSObject> object,
220                                     Handle<String> key,
221                                     Handle<Object> value,
222                                     PropertyDetails details);
223
224Handle<Object> ForceDeleteProperty(Handle<JSObject> object,
225                                   Handle<Object> key);
226
227Handle<Object> IgnoreAttributesAndSetLocalProperty(Handle<JSObject> object,
228                                                   Handle<String> key,
229                                                   Handle<Object> value,
230    PropertyAttributes attributes);
231
232Handle<Object> SetPropertyWithInterceptor(Handle<JSObject> object,
233                                          Handle<String> key,
234                                          Handle<Object> value,
235                                          PropertyAttributes attributes);
236
237Handle<Object> SetElement(Handle<JSObject> object,
238                          uint32_t index,
239                          Handle<Object> value);
240
241Handle<Object> GetProperty(Handle<JSObject> obj,
242                           const char* name);
243
244Handle<Object> GetProperty(Handle<Object> obj,
245                           Handle<Object> key);
246
247Handle<Object> GetElement(Handle<Object> obj,
248                          uint32_t index);
249
250Handle<Object> GetPropertyWithInterceptor(Handle<JSObject> receiver,
251                                          Handle<JSObject> holder,
252                                          Handle<String> name,
253                                          PropertyAttributes* attributes);
254
255Handle<Object> GetPrototype(Handle<Object> obj);
256
257Handle<Object> SetPrototype(Handle<JSObject> obj, Handle<Object> value);
258
259// Return the object's hidden properties object. If the object has no hidden
260// properties and create_if_needed is true, then a new hidden property object
261// will be allocated. Otherwise the Heap::undefined_value is returned.
262Handle<Object> GetHiddenProperties(Handle<JSObject> obj, bool create_if_needed);
263
264Handle<Object> DeleteElement(Handle<JSObject> obj, uint32_t index);
265Handle<Object> DeleteProperty(Handle<JSObject> obj, Handle<String> prop);
266
267Handle<Object> LookupSingleCharacterStringFromCode(uint32_t index);
268
269Handle<JSObject> Copy(Handle<JSObject> obj);
270
271Handle<Object> SetAccessor(Handle<JSObject> obj, Handle<AccessorInfo> info);
272
273Handle<FixedArray> AddKeysFromJSArray(Handle<FixedArray>,
274                                      Handle<JSArray> array);
275
276// Get the JS object corresponding to the given script; create it
277// if none exists.
278Handle<JSValue> GetScriptWrapper(Handle<Script> script);
279
280// Script line number computations.
281void InitScriptLineEnds(Handle<Script> script);
282// For string calculates an array of line end positions. If the string
283// does not end with a new line character, this character may optionally be
284// imagined.
285Handle<FixedArray> CalculateLineEnds(Handle<String> string,
286                                     bool with_imaginary_last_new_line);
287int GetScriptLineNumber(Handle<Script> script, int code_position);
288// The safe version does not make heap allocations but may work much slower.
289int GetScriptLineNumberSafe(Handle<Script> script, int code_position);
290
291// Computes the enumerable keys from interceptors. Used for debug mirrors and
292// by GetKeysInFixedArrayFor below.
293v8::Handle<v8::Array> GetKeysForNamedInterceptor(Handle<JSObject> receiver,
294                                                 Handle<JSObject> object);
295v8::Handle<v8::Array> GetKeysForIndexedInterceptor(Handle<JSObject> receiver,
296                                                   Handle<JSObject> object);
297
298enum KeyCollectionType { LOCAL_ONLY, INCLUDE_PROTOS };
299
300// Computes the enumerable keys for a JSObject. Used for implementing
301// "for (n in object) { }".
302Handle<FixedArray> GetKeysInFixedArrayFor(Handle<JSObject> object,
303                                          KeyCollectionType type);
304Handle<JSArray> GetKeysFor(Handle<JSObject> object);
305Handle<FixedArray> GetEnumPropertyKeys(Handle<JSObject> object,
306                                       bool cache_result);
307
308// Computes the union of keys and return the result.
309// Used for implementing "for (n in object) { }"
310Handle<FixedArray> UnionOfKeys(Handle<FixedArray> first,
311                               Handle<FixedArray> second);
312
313Handle<String> SubString(Handle<String> str,
314                         int start,
315                         int end,
316                         PretenureFlag pretenure = NOT_TENURED);
317
318
319// Sets the expected number of properties for the function's instances.
320void SetExpectedNofProperties(Handle<JSFunction> func, int nof);
321
322// Sets the prototype property for a function instance.
323void SetPrototypeProperty(Handle<JSFunction> func, Handle<JSObject> value);
324
325// Sets the expected number of properties based on estimate from compiler.
326void SetExpectedNofPropertiesFromEstimate(Handle<SharedFunctionInfo> shared,
327                                          int estimate);
328
329
330Handle<JSGlobalProxy> ReinitializeJSGlobalProxy(
331    Handle<JSFunction> constructor,
332    Handle<JSGlobalProxy> global);
333
334Handle<Object> SetPrototype(Handle<JSFunction> function,
335                            Handle<Object> prototype);
336
337
338// Does lazy compilation of the given function. Returns true on success and
339// false if the compilation resulted in a stack overflow.
340enum ClearExceptionFlag { KEEP_EXCEPTION, CLEAR_EXCEPTION };
341
342bool EnsureCompiled(Handle<SharedFunctionInfo> shared,
343                    ClearExceptionFlag flag);
344
345bool CompileLazyShared(Handle<SharedFunctionInfo> shared,
346                       ClearExceptionFlag flag);
347
348bool CompileLazy(Handle<JSFunction> function,
349                 Handle<Object> receiver,
350                 ClearExceptionFlag flag);
351
352bool CompileLazyInLoop(Handle<JSFunction> function,
353                       Handle<Object> receiver,
354                       ClearExceptionFlag flag);
355
356// Returns the lazy compilation stub for argc arguments.
357Handle<Code> ComputeLazyCompile(int argc);
358
359class NoHandleAllocation BASE_EMBEDDED {
360 public:
361#ifndef DEBUG
362  NoHandleAllocation() {}
363  ~NoHandleAllocation() {}
364#else
365  inline NoHandleAllocation();
366  inline ~NoHandleAllocation();
367 private:
368  int extensions_;
369#endif
370};
371
372
373// ----------------------------------------------------------------------------
374
375
376// Stack allocated wrapper call for optimizing adding multiple
377// properties to an object.
378class OptimizedObjectForAddingMultipleProperties BASE_EMBEDDED {
379 public:
380  OptimizedObjectForAddingMultipleProperties(Handle<JSObject> object,
381                                             int expected_property_count,
382                                             bool condition = true);
383  ~OptimizedObjectForAddingMultipleProperties();
384 private:
385  bool has_been_transformed_;  // Tells whether the object has been transformed.
386  int unused_property_fields_;  // Captures the unused number of field.
387  Handle<JSObject> object_;    // The object being optimized.
388};
389
390
391} }  // namespace v8::internal
392
393#endif  // V8_HANDLES_H_
394