src/api.h

   1 // Copyright 2012 the V8 project authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef V8_API_H_
   6 #define V8_API_H_
   7
   8 #include "src/v8.h"
   9
  10 #include "include/v8-testing.h"
  11 #include "src/contexts.h"
  12 #include "src/factory.h"
  13 #include "src/isolate.h"
  14 #include "src/list-inl.h"
  15
  16 namespace v8 {
  17
  18 // Constants used in the implementation of the API.  The most natural thing
  19 // would usually be to place these with the classes that use them, but
  20 // we want to keep them out of v8.h because it is an externally
  21 // visible file.
  22 class Consts {
  23  public:
  24   enum TemplateType {
  25     FUNCTION_TEMPLATE = 0,
  26     OBJECT_TEMPLATE = 1
  27   };
  28 };
  29
  30
  31 // Utilities for working with neander-objects, primitive
  32 // env-independent JSObjects used by the api.
  33 class NeanderObject {
  34  public:
  35   explicit NeanderObject(v8::internal::Isolate* isolate, int size);
  36   explicit inline NeanderObject(v8::internal::Handle<v8::internal::Object> obj);
  37   explicit inline NeanderObject(v8::internal::Object* obj);
  38   inline v8::internal::Object* get(int index);
  39   inline void set(int index, v8::internal::Object* value);
  40   inline v8::internal::Handle<v8::internal::JSObject> value() { return value_; }
  41   int size();
  42  private:
  43   v8::internal::Handle<v8::internal::JSObject> value_;
  44 };
  45
  46
  47 // Utilities for working with neander-arrays, a simple extensible
  48 // array abstraction built on neander-objects.
  49 class NeanderArray {
  50  public:
  51   explicit NeanderArray(v8::internal::Isolate* isolate);
  52   explicit inline NeanderArray(v8::internal::Handle<v8::internal::Object> obj);
  53   inline v8::internal::Handle<v8::internal::JSObject> value() {
  54     return obj_.value();
  55   }
  56
  57   void add(internal::Isolate* isolate,
  58            v8::internal::Handle<v8::internal::Object> value);
  59
  60   int length();
  61
  62   v8::internal::Object* get(int index);
  63   // Change the value at an index to undefined value. If the index is
  64   // out of bounds, the request is ignored. Returns the old value.
  65   void set(int index, v8::internal::Object* value);
  66  private:
  67   NeanderObject obj_;
  68 };
  69
  70
  71 NeanderObject::NeanderObject(v8::internal::Handle<v8::internal::Object> obj)
  72     : value_(v8::internal::Handle<v8::internal::JSObject>::cast(obj)) { }
  73
  74
  75 NeanderObject::NeanderObject(v8::internal::Object* obj)
  76     : value_(v8::internal::Handle<v8::internal::JSObject>(
  77         v8::internal::JSObject::cast(obj))) { }
  78
  79
  80 NeanderArray::NeanderArray(v8::internal::Handle<v8::internal::Object> obj)
  81     : obj_(obj) { }
  82
  83
  84 v8::internal::Object* NeanderObject::get(int offset) {
  85   DCHECK(value()->HasFastObjectElements());
  86   return v8::internal::FixedArray::cast(value()->elements())->get(offset);
  87 }
  88
  89
  90 void NeanderObject::set(int offset, v8::internal::Object* value) {
  91   DCHECK(value_->HasFastObjectElements());
  92   v8::internal::FixedArray::cast(value_->elements())->set(offset, value);
  93 }
  94
  95
  96 template <typename T> inline T ToCData(v8::internal::Object* obj) {
  97   STATIC_ASSERT(sizeof(T) == sizeof(v8::internal::Address));
  98   return reinterpret_cast<T>(
  99       reinterpret_cast<intptr_t>(
 100           v8::internal::Foreign::cast(obj)->foreign_address()));
 101 }
 102
 103
 104 template <typename T>
 105 inline v8::internal::Handle<v8::internal::Object> FromCData(
 106     v8::internal::Isolate* isolate, T obj) {
 107   STATIC_ASSERT(sizeof(T) == sizeof(v8::internal::Address));
 108   return isolate->factory()->NewForeign(
 109       reinterpret_cast<v8::internal::Address>(reinterpret_cast<intptr_t>(obj)));
 110 }
 111
 112
 113 class ApiFunction {
 114  public:
 115   explicit ApiFunction(v8::internal::Address addr) : addr_(addr) { }
 116   v8::internal::Address address() { return addr_; }
 117  private:
 118   v8::internal::Address addr_;
 119 };
 120
 121
 122
 123 class RegisteredExtension {
 124  public:
 125   explicit RegisteredExtension(Extension* extension);
 126   static void Register(RegisteredExtension* that);
 127   static void UnregisterAll();
 128   Extension* extension() { return extension_; }
 129   RegisteredExtension* next() { return next_; }
 130   static RegisteredExtension* first_extension() { return first_extension_; }
 131  private:
 132   Extension* extension_;
 133   RegisteredExtension* next_;
 134   static RegisteredExtension* first_extension_;
 135 };
 136
 137
 138 #define OPEN_HANDLE_LIST(V)                  \
 139   V(Template, TemplateInfo)                  \
 140   V(FunctionTemplate, FunctionTemplateInfo)  \
 141   V(ObjectTemplate, ObjectTemplateInfo)      \
 142   V(Signature, SignatureInfo)                \
 143   V(AccessorSignature, FunctionTemplateInfo) \
 144   V(TypeSwitch, TypeSwitchInfo)              \
 145   V(Data, Object)                            \
 146   V(RegExp, JSRegExp)                        \
 147   V(Object, JSObject)                        \
 148   V(Array, JSArray)                          \
 149   V(ArrayBuffer, JSArrayBuffer)              \
 150   V(ArrayBufferView, JSArrayBufferView)      \
 151   V(TypedArray, JSTypedArray)                \
 152   V(Uint8Array, JSTypedArray)                \
 153   V(Uint8ClampedArray, JSTypedArray)         \
 154   V(Int8Array, JSTypedArray)                 \
 155   V(Uint16Array, JSTypedArray)               \
 156   V(Int16Array, JSTypedArray)                \
 157   V(Uint32Array, JSTypedArray)               \
 158   V(Int32Array, JSTypedArray)                \
 159   V(Float32Array, JSTypedArray)              \
 160   V(Float64Array, JSTypedArray)              \
 161   V(DataView, JSDataView)                    \
 162   V(Name, Name)                              \
 163   V(String, String)                          \
 164   V(Symbol, Symbol)                          \
 165   V(Script, JSFunction)                      \
 166   V(UnboundScript, SharedFunctionInfo)       \
 167   V(Function, JSFunction)                    \
 168   V(Message, JSMessageObject)                \
 169   V(Context, Context)                        \
 170   V(External, Object)                        \
 171   V(StackTrace, JSArray)                     \
 172   V(StackFrame, JSObject)
 173
 174 class Utils {
 175  public:
 176   static inline bool ApiCheck(bool condition,
 177                               const char* location,
 178                               const char* message) {
 179     if (!condition) Utils::ReportApiFailure(location, message);
 180     return condition;
 181   }
 182
 183   static Local<FunctionTemplate> ToFunctionTemplate(NeanderObject obj);
 184   static Local<ObjectTemplate> ToObjectTemplate(NeanderObject obj);
 185
 186   static inline Local<Context> ToLocal(
 187       v8::internal::Handle<v8::internal::Context> obj);
 188   static inline Local<Value> ToLocal(
 189       v8::internal::Handle<v8::internal::Object> obj);
 190   static inline Local<Function> ToLocal(
 191       v8::internal::Handle<v8::internal::JSFunction> obj);
 192   static inline Local<Name> ToLocal(
 193       v8::internal::Handle<v8::internal::Name> obj);
 194   static inline Local<String> ToLocal(
 195       v8::internal::Handle<v8::internal::String> obj);
 196   static inline Local<Symbol> ToLocal(
 197       v8::internal::Handle<v8::internal::Symbol> obj);
 198   static inline Local<RegExp> ToLocal(
 199       v8::internal::Handle<v8::internal::JSRegExp> obj);
 200   static inline Local<Object> ToLocal(
 201       v8::internal::Handle<v8::internal::JSObject> obj);
 202   static inline Local<Array> ToLocal(
 203       v8::internal::Handle<v8::internal::JSArray> obj);
 204   static inline Local<ArrayBuffer> ToLocal(
 205       v8::internal::Handle<v8::internal::JSArrayBuffer> obj);
 206   static inline Local<ArrayBufferView> ToLocal(
 207       v8::internal::Handle<v8::internal::JSArrayBufferView> obj);
 208   static inline Local<DataView> ToLocal(
 209       v8::internal::Handle<v8::internal::JSDataView> obj);
 210
 211   static inline Local<TypedArray> ToLocal(
 212       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 213   static inline Local<Uint8Array> ToLocalUint8Array(
 214       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 215   static inline Local<Uint8ClampedArray> ToLocalUint8ClampedArray(
 216       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 217   static inline Local<Int8Array> ToLocalInt8Array(
 218       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 219   static inline Local<Uint16Array> ToLocalUint16Array(
 220       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 221   static inline Local<Int16Array> ToLocalInt16Array(
 222       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 223   static inline Local<Uint32Array> ToLocalUint32Array(
 224       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 225   static inline Local<Int32Array> ToLocalInt32Array(
 226       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 227   static inline Local<Float32Array> ToLocalFloat32Array(
 228       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 229   static inline Local<Float64Array> ToLocalFloat64Array(
 230       v8::internal::Handle<v8::internal::JSTypedArray> obj);
 231
 232   static inline Local<Message> MessageToLocal(
 233       v8::internal::Handle<v8::internal::Object> obj);
 234   static inline Local<Promise> PromiseToLocal(
 235       v8::internal::Handle<v8::internal::JSObject> obj);
 236   static inline Local<StackTrace> StackTraceToLocal(
 237       v8::internal::Handle<v8::internal::JSArray> obj);
 238   static inline Local<StackFrame> StackFrameToLocal(
 239       v8::internal::Handle<v8::internal::JSObject> obj);
 240   static inline Local<Number> NumberToLocal(
 241       v8::internal::Handle<v8::internal::Object> obj);
 242   static inline Local<Integer> IntegerToLocal(
 243       v8::internal::Handle<v8::internal::Object> obj);
 244   static inline Local<Uint32> Uint32ToLocal(
 245       v8::internal::Handle<v8::internal::Object> obj);
 246   static inline Local<FunctionTemplate> ToLocal(
 247       v8::internal::Handle<v8::internal::FunctionTemplateInfo> obj);
 248   static inline Local<ObjectTemplate> ToLocal(
 249       v8::internal::Handle<v8::internal::ObjectTemplateInfo> obj);
 250   static inline Local<Signature> ToLocal(
 251       v8::internal::Handle<v8::internal::SignatureInfo> obj);
 252   static inline Local<AccessorSignature> AccessorSignatureToLocal(
 253       v8::internal::Handle<v8::internal::FunctionTemplateInfo> obj);
 254   static inline Local<TypeSwitch> ToLocal(
 255       v8::internal::Handle<v8::internal::TypeSwitchInfo> obj);
 256   static inline Local<External> ExternalToLocal(
 257       v8::internal::Handle<v8::internal::JSObject> obj);
 258
 259 #define DECLARE_OPEN_HANDLE(From, To) \
 260   static inline v8::internal::Handle<v8::internal::To> \
 261       OpenHandle(const From* that, bool allow_empty_handle = false);
 262
 263 OPEN_HANDLE_LIST(DECLARE_OPEN_HANDLE)
 264
 265 #undef DECLARE_OPEN_HANDLE
 266
 267   template<class From, class To>
 268   static inline Local<To> Convert(v8::internal::Handle<From> obj) {
 269     DCHECK(obj.is_null() || !obj->IsTheHole());
 270     return Local<To>(reinterpret_cast<To*>(obj.location()));
 271   }
 272
 273   template <class T>
 274   static inline v8::internal::Handle<v8::internal::Object> OpenPersistent(
 275       const v8::Persistent<T>& persistent) {
 276     return v8::internal::Handle<v8::internal::Object>(
 277         reinterpret_cast<v8::internal::Object**>(persistent.val_));
 278   }
 279
 280   template <class T>
 281   static inline v8::internal::Handle<v8::internal::Object> OpenPersistent(
 282       v8::Persistent<T>* persistent) {
 283     return OpenPersistent(*persistent);
 284   }
 285
 286   template <class From, class To>
 287   static inline v8::internal::Handle<To> OpenHandle(v8::Local<From> handle) {
 288     return OpenHandle(*handle);
 289   }
 290
 291  private:
 292   static void ReportApiFailure(const char* location, const char* message);
 293 };
 294
 295
 296 template <class T>
 297 v8::internal::Handle<T> v8::internal::Handle<T>::EscapeFrom(
 298     v8::EscapableHandleScope* scope) {
 299   v8::internal::Handle<T> handle;
 300   if (!is_null()) {
 301     handle = *this;
 302   }
 303   return Utils::OpenHandle(*scope->Escape(Utils::ToLocal(handle)), true);
 304 }
 305
 306
 307 template <class T>
 308 inline T* ToApi(v8::internal::Handle<v8::internal::Object> obj) {
 309   return reinterpret_cast<T*>(obj.location());
 310 }
 311
 312 template <class T>
 313 inline v8::Local<T> ToApiHandle(
 314     v8::internal::Handle<v8::internal::Object> obj) {
 315   return Utils::Convert<v8::internal::Object, T>(obj);
 316 }
 317
 318
 319 // Implementations of ToLocal
 320
 321 #define MAKE_TO_LOCAL(Name, From, To)                                       \
 322   Local<v8::To> Utils::Name(v8::internal::Handle<v8::internal::From> obj) { \
 323     return Convert<v8::internal::From, v8::To>(obj);  \
 324   }
 325
 326
 327 #define MAKE_TO_LOCAL_TYPED_ARRAY(Type, typeName, TYPE, ctype, size)        \
 328   Local<v8::Type##Array> Utils::ToLocal##Type##Array(                       \
 329       v8::internal::Handle<v8::internal::JSTypedArray> obj) {               \
 330     DCHECK(obj->type() == kExternal##Type##Array);                          \
 331     return Convert<v8::internal::JSTypedArray, v8::Type##Array>(obj);       \
 332   }
 333
 334
 335 MAKE_TO_LOCAL(ToLocal, Context, Context)
 336 MAKE_TO_LOCAL(ToLocal, Object, Value)
 337 MAKE_TO_LOCAL(ToLocal, JSFunction, Function)
 338 MAKE_TO_LOCAL(ToLocal, Name, Name)
 339 MAKE_TO_LOCAL(ToLocal, String, String)
 340 MAKE_TO_LOCAL(ToLocal, Symbol, Symbol)
 341 MAKE_TO_LOCAL(ToLocal, JSRegExp, RegExp)
 342 MAKE_TO_LOCAL(ToLocal, JSObject, Object)
 343 MAKE_TO_LOCAL(ToLocal, JSArray, Array)
 344 MAKE_TO_LOCAL(ToLocal, JSArrayBuffer, ArrayBuffer)
 345 MAKE_TO_LOCAL(ToLocal, JSArrayBufferView, ArrayBufferView)
 346 MAKE_TO_LOCAL(ToLocal, JSDataView, DataView)
 347 MAKE_TO_LOCAL(ToLocal, JSTypedArray, TypedArray)
 348
 349 TYPED_ARRAYS(MAKE_TO_LOCAL_TYPED_ARRAY)
 350
 351 MAKE_TO_LOCAL(ToLocal, FunctionTemplateInfo, FunctionTemplate)
 352 MAKE_TO_LOCAL(ToLocal, ObjectTemplateInfo, ObjectTemplate)
 353 MAKE_TO_LOCAL(ToLocal, SignatureInfo, Signature)
 354 MAKE_TO_LOCAL(AccessorSignatureToLocal, FunctionTemplateInfo, AccessorSignature)
 355 MAKE_TO_LOCAL(ToLocal, TypeSwitchInfo, TypeSwitch)
 356 MAKE_TO_LOCAL(MessageToLocal, Object, Message)
 357 MAKE_TO_LOCAL(PromiseToLocal, JSObject, Promise)
 358 MAKE_TO_LOCAL(StackTraceToLocal, JSArray, StackTrace)
 359 MAKE_TO_LOCAL(StackFrameToLocal, JSObject, StackFrame)
 360 MAKE_TO_LOCAL(NumberToLocal, Object, Number)
 361 MAKE_TO_LOCAL(IntegerToLocal, Object, Integer)
 362 MAKE_TO_LOCAL(Uint32ToLocal, Object, Uint32)
 363 MAKE_TO_LOCAL(ExternalToLocal, JSObject, External)
 364
 365 #undef MAKE_TO_LOCAL_TYPED_ARRAY
 366 #undef MAKE_TO_LOCAL
 367
 368
 369 // Implementations of OpenHandle
 370
 371 #define MAKE_OPEN_HANDLE(From, To)                                          \
 372   v8::internal::Handle<v8::internal::To> Utils::OpenHandle(                 \
 373     const v8::From* that, bool allow_empty_handle) {                        \
 374     EXTRA_CHECK(allow_empty_handle || that != NULL);                        \
 375     EXTRA_CHECK(that == NULL ||                                             \
 376         (*reinterpret_cast<v8::internal::Object* const*>(that))->Is##To()); \
 377     return v8::internal::Handle<v8::internal::To>(                          \
 378         reinterpret_cast<v8::internal::To**>(const_cast<v8::From*>(that))); \
 379   }
 380
 381 OPEN_HANDLE_LIST(MAKE_OPEN_HANDLE)
 382
 383 #undef MAKE_OPEN_HANDLE
 384 #undef OPEN_HANDLE_LIST
 385
 386
 387 namespace internal {
 388
 389 // Tracks string usage to help make better decisions when
 390 // externalizing strings.
 391 //
 392 // Implementation note: internally this class only tracks fresh
 393 // strings and keeps a single use counter for them.
 394 class StringTracker {
 395  public:
 396   // Records that the given string's characters were copied to some
 397   // external buffer. If this happens often we should honor
 398   // externalization requests for the string.
 399   void RecordWrite(Handle<String> string) {
 400     Address address = reinterpret_cast<Address>(*string);
 401     Address top = isolate_->heap()->NewSpaceTop();
 402     if (IsFreshString(address, top)) {
 403       IncrementUseCount(top);
 404     }
 405   }
 406
 407   // Estimates freshness and use frequency of the given string based
 408   // on how close it is to the new space top and the recorded usage
 409   // history.
 410   inline bool IsFreshUnusedString(Handle<String> string) {
 411     Address address = reinterpret_cast<Address>(*string);
 412     Address top = isolate_->heap()->NewSpaceTop();
 413     return IsFreshString(address, top) && IsUseCountLow(top);
 414   }
 415
 416  private:
 417   StringTracker() : use_count_(0), last_top_(NULL), isolate_(NULL) { }
 418
 419   static inline bool IsFreshString(Address string, Address top) {
 420     return top - kFreshnessLimit <= string && string <= top;
 421   }
 422
 423   inline bool IsUseCountLow(Address top) {
 424     if (last_top_ != top) return true;
 425     return use_count_ < kUseLimit;
 426   }
 427
 428   inline void IncrementUseCount(Address top) {
 429     if (last_top_ != top) {
 430       use_count_ = 0;
 431       last_top_ = top;
 432     }
 433     ++use_count_;
 434   }
 435
 436   // Single use counter shared by all fresh strings.
 437   int use_count_;
 438
 439   // Last new space top when the use count above was valid.
 440   Address last_top_;
 441
 442   Isolate* isolate_;
 443
 444   // How close to the new space top a fresh string has to be.
 445   static const int kFreshnessLimit = 1024;
 446
 447   // The number of uses required to consider a string useful.
 448   static const int kUseLimit = 32;
 449
 450   friend class Isolate;
 451
 452   DISALLOW_COPY_AND_ASSIGN(StringTracker);
 453 };
 454
 455
 456 class DeferredHandles {
 457  public:
 458   ~DeferredHandles();
 459
 460  private:
 461   DeferredHandles(Object** first_block_limit, Isolate* isolate)
 462       : next_(NULL),
 463         previous_(NULL),
 464         first_block_limit_(first_block_limit),
 465         isolate_(isolate) {
 466     isolate->LinkDeferredHandles(this);
 467   }
 468
 469   void Iterate(ObjectVisitor* v);
 470
 471   List<Object**> blocks_;
 472   DeferredHandles* next_;
 473   DeferredHandles* previous_;
 474   Object** first_block_limit_;
 475   Isolate* isolate_;
 476
 477   friend class HandleScopeImplementer;
 478   friend class Isolate;
 479 };
 480
 481
 482 // This class is here in order to be able to declare it a friend of
 483 // HandleScope.  Moving these methods to be members of HandleScope would be
 484 // neat in some ways, but it would expose internal implementation details in
 485 // our public header file, which is undesirable.
 486 //
 487 // An isolate has a single instance of this class to hold the current thread's
 488 // data. In multithreaded V8 programs this data is copied in and out of storage
 489 // so that the currently executing thread always has its own copy of this
 490 // data.
 491 class HandleScopeImplementer {
 492  public:
 493   explicit HandleScopeImplementer(Isolate* isolate)
 494       : isolate_(isolate),
 495         blocks_(0),
 496         entered_contexts_(0),
 497         saved_contexts_(0),
 498         spare_(NULL),
 499         call_depth_(0),
 500         last_handle_before_deferred_block_(NULL) { }
 501
 502   ~HandleScopeImplementer() {
 503     DeleteArray(spare_);
 504   }
 505
 506   // Threading support for handle data.
 507   static int ArchiveSpacePerThread();
 508   char* RestoreThread(char* from);
 509   char* ArchiveThread(char* to);
 510   void FreeThreadResources();
 511
 512   // Garbage collection support.
 513   void Iterate(v8::internal::ObjectVisitor* v);
 514   static char* Iterate(v8::internal::ObjectVisitor* v, char* data);
 515
 516
 517   inline internal::Object** GetSpareOrNewBlock();
 518   inline void DeleteExtensions(internal::Object** prev_limit);
 519
 520   inline void IncrementCallDepth() {call_depth_++;}
 521   inline void DecrementCallDepth() {call_depth_--;}
 522   inline bool CallDepthIsZero() { return call_depth_ == 0; }
 523
 524   inline void EnterContext(Handle<Context> context);
 525   inline void LeaveContext();
 526   inline bool LastEnteredContextWas(Handle<Context> context);
 527
 528   // Returns the last entered context or an empty handle if no
 529   // contexts have been entered.
 530   inline Handle<Context> LastEnteredContext();
 531
 532   inline void SaveContext(Context* context);
 533   inline Context* RestoreContext();
 534   inline bool HasSavedContexts();
 535
 536   inline List<internal::Object**>* blocks() { return &blocks_; }
 537   Isolate* isolate() const { return isolate_; }
 538
 539   void ReturnBlock(Object** block) {
 540     DCHECK(block != NULL);
 541     if (spare_ != NULL) DeleteArray(spare_);
 542     spare_ = block;
 543   }
 544
 545  private:
 546   void ResetAfterArchive() {
 547     blocks_.Initialize(0);
 548     entered_contexts_.Initialize(0);
 549     saved_contexts_.Initialize(0);
 550     spare_ = NULL;
 551     last_handle_before_deferred_block_ = NULL;
 552     call_depth_ = 0;
 553   }
 554
 555   void Free() {
 556     DCHECK(blocks_.length() == 0);
 557     DCHECK(entered_contexts_.length() == 0);
 558     DCHECK(saved_contexts_.length() == 0);
 559     blocks_.Free();
 560     entered_contexts_.Free();
 561     saved_contexts_.Free();
 562     if (spare_ != NULL) {
 563       DeleteArray(spare_);
 564       spare_ = NULL;
 565     }
 566     DCHECK(call_depth_ == 0);
 567   }
 568
 569   void BeginDeferredScope();
 570   DeferredHandles* Detach(Object** prev_limit);
 571
 572   Isolate* isolate_;
 573   List<internal::Object**> blocks_;
 574   // Used as a stack to keep track of entered contexts.
 575   List<Context*> entered_contexts_;
 576   // Used as a stack to keep track of saved contexts.
 577   List<Context*> saved_contexts_;
 578   Object** spare_;
 579   int call_depth_;
 580   Object** last_handle_before_deferred_block_;
 581   // This is only used for threading support.
 582   HandleScopeData handle_scope_data_;
 583
 584   void IterateThis(ObjectVisitor* v);
 585   char* RestoreThreadHelper(char* from);
 586   char* ArchiveThreadHelper(char* to);
 587
 588   friend class DeferredHandles;
 589   friend class DeferredHandleScope;
 590
 591   DISALLOW_COPY_AND_ASSIGN(HandleScopeImplementer);
 592 };
 593
 594
 595 const int kHandleBlockSize = v8::internal::KB - 2;  // fit in one page
 596
 597
 598 void HandleScopeImplementer::SaveContext(Context* context) {
 599   saved_contexts_.Add(context);
 600 }
 601
 602
 603 Context* HandleScopeImplementer::RestoreContext() {
 604   return saved_contexts_.RemoveLast();
 605 }
 606
 607
 608 bool HandleScopeImplementer::HasSavedContexts() {
 609   return !saved_contexts_.is_empty();
 610 }
 611
 612
 613 void HandleScopeImplementer::EnterContext(Handle<Context> context) {
 614   entered_contexts_.Add(*context);
 615 }
 616
 617
 618 void HandleScopeImplementer::LeaveContext() {
 619   entered_contexts_.RemoveLast();
 620 }
 621
 622
 623 bool HandleScopeImplementer::LastEnteredContextWas(Handle<Context> context) {
 624   return !entered_contexts_.is_empty() && entered_contexts_.last() == *context;
 625 }
 626
 627
 628 Handle<Context> HandleScopeImplementer::LastEnteredContext() {
 629   if (entered_contexts_.is_empty()) return Handle<Context>::null();
 630   return Handle<Context>(entered_contexts_.last());
 631 }
 632
 633
 634 // If there's a spare block, use it for growing the current scope.
 635 internal::Object** HandleScopeImplementer::GetSpareOrNewBlock() {
 636   internal::Object** block = (spare_ != NULL) ?
 637       spare_ :
 638       NewArray<internal::Object*>(kHandleBlockSize);
 639   spare_ = NULL;
 640   return block;
 641 }
 642
 643
 644 void HandleScopeImplementer::DeleteExtensions(internal::Object** prev_limit) {
 645   while (!blocks_.is_empty()) {
 646     internal::Object** block_start = blocks_.last();
 647     internal::Object** block_limit = block_start + kHandleBlockSize;
 648 #ifdef DEBUG
 649     // SealHandleScope may make the prev_limit to point inside the block.
 650     if (block_start <= prev_limit && prev_limit <= block_limit) {
 651 #ifdef ENABLE_HANDLE_ZAPPING
 652       internal::HandleScope::ZapRange(prev_limit, block_limit);
 653 #endif
 654       break;
 655     }
 656 #else
 657     if (prev_limit == block_limit) break;
 658 #endif
 659
 660     blocks_.RemoveLast();
 661 #ifdef ENABLE_HANDLE_ZAPPING
 662     internal::HandleScope::ZapRange(block_start, block_limit);
 663 #endif
 664     if (spare_ != NULL) {
 665       DeleteArray(spare_);
 666     }
 667     spare_ = block_start;
 668   }
 669   DCHECK((blocks_.is_empty() && prev_limit == NULL) ||
 670          (!blocks_.is_empty() && prev_limit != NULL));
 671 }
 672
 673
 674 // Interceptor functions called from generated inline caches to notify
 675 // CPU profiler that external callbacks are invoked.
 676 void InvokeAccessorGetterCallback(
 677     v8::Local<v8::Name> property,
 678     const v8::PropertyCallbackInfo<v8::Value>& info,
 679     v8::AccessorNameGetterCallback getter);
 680
 681 void InvokeFunctionCallback(const v8::FunctionCallbackInfo<v8::Value>& info,
 682                             v8::FunctionCallback callback);
 683
 684 class Testing {
 685  public:
 686   static v8::Testing::StressType stress_type() { return stress_type_; }
 687   static void set_stress_type(v8::Testing::StressType stress_type) {
 688     stress_type_ = stress_type;
 689   }
 690
 691  private:
 692   static v8::Testing::StressType stress_type_;
 693 };
 694
 695 } }  // namespace v8::internal
 696
 697 #endif  // V8_API_H_