src/api.h

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