src/api.h

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