src/api.h

   1 // Copyright 2012 the V8 project authors. All rights reserved.
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   4 // met:
   5 //
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   7 //       notice, this list of conditions and the following disclaimer.
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   9 //       copyright notice, this list of conditions and the following
  10 //       disclaimer in the documentation and/or other materials provided
  11 //       with the distribution.
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  14 //       from this software without specific prior written permission.
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  26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  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 // Implementations of ToLocal
 298
 299 #define MAKE_TO_LOCAL(Name, From, To)                                       \
 300   Local<v8::To> Utils::Name(v8::internal::Handle<v8::internal::From> obj) { \
 301     ASSERT(obj.is_null() || !obj->IsTheHole());                             \
 302     return Local<To>(reinterpret_cast<To*>(obj.location()));                \
 303   }
 304
 305
 306 #define MAKE_TO_LOCAL_TYPED_ARRAY(TypedArray, typeConst)                    \
 307   Local<v8::TypedArray> Utils::ToLocal##TypedArray(                         \
 308       v8::internal::Handle<v8::internal::JSTypedArray> obj) {               \
 309     ASSERT(obj.is_null() || !obj->IsTheHole());                             \
 310     ASSERT(obj->type() == typeConst);                                       \
 311     return Local<v8::TypedArray>(                                           \
 312         reinterpret_cast<v8::TypedArray*>(obj.location()));                 \
 313   }
 314
 315
 316 MAKE_TO_LOCAL(ToLocal, Context, Context)
 317 MAKE_TO_LOCAL(ToLocal, Object, Value)
 318 MAKE_TO_LOCAL(ToLocal, JSFunction, Function)
 319 MAKE_TO_LOCAL(ToLocal, String, String)
 320 MAKE_TO_LOCAL(ToLocal, Symbol, Symbol)
 321 MAKE_TO_LOCAL(ToLocal, JSRegExp, RegExp)
 322 MAKE_TO_LOCAL(ToLocal, JSObject, Object)
 323 MAKE_TO_LOCAL(ToLocal, JSArray, Array)
 324 MAKE_TO_LOCAL(ToLocal, JSArrayBuffer, ArrayBuffer)
 325 MAKE_TO_LOCAL(ToLocal, JSTypedArray, TypedArray)
 326
 327 MAKE_TO_LOCAL_TYPED_ARRAY(Uint8Array, kExternalUnsignedByteArray)
 328 MAKE_TO_LOCAL_TYPED_ARRAY(Uint8ClampedArray, kExternalPixelArray)
 329 MAKE_TO_LOCAL_TYPED_ARRAY(Int8Array, kExternalByteArray)
 330 MAKE_TO_LOCAL_TYPED_ARRAY(Uint16Array, kExternalUnsignedShortArray)
 331 MAKE_TO_LOCAL_TYPED_ARRAY(Int16Array, kExternalShortArray)
 332 MAKE_TO_LOCAL_TYPED_ARRAY(Uint32Array, kExternalUnsignedIntArray)
 333 MAKE_TO_LOCAL_TYPED_ARRAY(Int32Array, kExternalIntArray)
 334 MAKE_TO_LOCAL_TYPED_ARRAY(Float32Array, kExternalFloatArray)
 335 MAKE_TO_LOCAL_TYPED_ARRAY(Float64Array, kExternalDoubleArray)
 336
 337 MAKE_TO_LOCAL(ToLocal, FunctionTemplateInfo, FunctionTemplate)
 338 MAKE_TO_LOCAL(ToLocal, ObjectTemplateInfo, ObjectTemplate)
 339 MAKE_TO_LOCAL(ToLocal, SignatureInfo, Signature)
 340 MAKE_TO_LOCAL(AccessorSignatureToLocal, FunctionTemplateInfo, AccessorSignature)
 341 MAKE_TO_LOCAL(ToLocal, TypeSwitchInfo, TypeSwitch)
 342 MAKE_TO_LOCAL(MessageToLocal, Object, Message)
 343 MAKE_TO_LOCAL(StackTraceToLocal, JSArray, StackTrace)
 344 MAKE_TO_LOCAL(StackFrameToLocal, JSObject, StackFrame)
 345 MAKE_TO_LOCAL(NumberToLocal, Object, Number)
 346 MAKE_TO_LOCAL(IntegerToLocal, Object, Integer)
 347 MAKE_TO_LOCAL(Uint32ToLocal, Object, Uint32)
 348 MAKE_TO_LOCAL(ExternalToLocal, JSObject, External)
 349 MAKE_TO_LOCAL(ToLocal, DeclaredAccessorDescriptor, DeclaredAccessorDescriptor)
 350
 351 #undef MAKE_TO_LOCAL_TYPED_ARRAY
 352 #undef MAKE_TO_LOCAL
 353
 354
 355 // Implementations of OpenHandle
 356
 357 #define MAKE_OPEN_HANDLE(From, To)                                          \
 358   v8::internal::Handle<v8::internal::To> Utils::OpenHandle(                 \
 359     const v8::From* that, bool allow_empty_handle) {                        \
 360     EXTRA_CHECK(allow_empty_handle || that != NULL);                        \
 361     EXTRA_CHECK(that == NULL ||                                             \
 362         !(*reinterpret_cast<v8::internal::To**>(                            \
 363             const_cast<v8::From*>(that)))->IsFailure());                    \
 364     return v8::internal::Handle<v8::internal::To>(                          \
 365         reinterpret_cast<v8::internal::To**>(const_cast<v8::From*>(that))); \
 366   }
 367
 368 OPEN_HANDLE_LIST(MAKE_OPEN_HANDLE)
 369
 370 #undef MAKE_OPEN_HANDLE
 371 #undef OPEN_HANDLE_LIST
 372
 373
 374 namespace internal {
 375
 376 // Tracks string usage to help make better decisions when
 377 // externalizing strings.
 378 //
 379 // Implementation note: internally this class only tracks fresh
 380 // strings and keeps a single use counter for them.
 381 class StringTracker {
 382  public:
 383   // Records that the given string's characters were copied to some
 384   // external buffer. If this happens often we should honor
 385   // externalization requests for the string.
 386   void RecordWrite(Handle<String> string) {
 387     Address address = reinterpret_cast<Address>(*string);
 388     Address top = isolate_->heap()->NewSpaceTop();
 389     if (IsFreshString(address, top)) {
 390       IncrementUseCount(top);
 391     }
 392   }
 393
 394   // Estimates freshness and use frequency of the given string based
 395   // on how close it is to the new space top and the recorded usage
 396   // history.
 397   inline bool IsFreshUnusedString(Handle<String> string) {
 398     Address address = reinterpret_cast<Address>(*string);
 399     Address top = isolate_->heap()->NewSpaceTop();
 400     return IsFreshString(address, top) && IsUseCountLow(top);
 401   }
 402
 403  private:
 404   StringTracker() : use_count_(0), last_top_(NULL), isolate_(NULL) { }
 405
 406   static inline bool IsFreshString(Address string, Address top) {
 407     return top - kFreshnessLimit <= string && string <= top;
 408   }
 409
 410   inline bool IsUseCountLow(Address top) {
 411     if (last_top_ != top) return true;
 412     return use_count_ < kUseLimit;
 413   }
 414
 415   inline void IncrementUseCount(Address top) {
 416     if (last_top_ != top) {
 417       use_count_ = 0;
 418       last_top_ = top;
 419     }
 420     ++use_count_;
 421   }
 422
 423   // Single use counter shared by all fresh strings.
 424   int use_count_;
 425
 426   // Last new space top when the use count above was valid.
 427   Address last_top_;
 428
 429   Isolate* isolate_;
 430
 431   // How close to the new space top a fresh string has to be.
 432   static const int kFreshnessLimit = 1024;
 433
 434   // The number of uses required to consider a string useful.
 435   static const int kUseLimit = 32;
 436
 437   friend class Isolate;
 438
 439   DISALLOW_COPY_AND_ASSIGN(StringTracker);
 440 };
 441
 442
 443 class DeferredHandles {
 444  public:
 445   ~DeferredHandles();
 446
 447  private:
 448   DeferredHandles(Object** first_block_limit, Isolate* isolate)
 449       : next_(NULL),
 450         previous_(NULL),
 451         first_block_limit_(first_block_limit),
 452         isolate_(isolate) {
 453     isolate->LinkDeferredHandles(this);
 454   }
 455
 456   void Iterate(ObjectVisitor* v);
 457
 458   List<Object**> blocks_;
 459   DeferredHandles* next_;
 460   DeferredHandles* previous_;
 461   Object** first_block_limit_;
 462   Isolate* isolate_;
 463
 464   friend class HandleScopeImplementer;
 465   friend class Isolate;
 466 };
 467
 468
 469 // This class is here in order to be able to declare it a friend of
 470 // HandleScope.  Moving these methods to be members of HandleScope would be
 471 // neat in some ways, but it would expose internal implementation details in
 472 // our public header file, which is undesirable.
 473 //
 474 // An isolate has a single instance of this class to hold the current thread's
 475 // data. In multithreaded V8 programs this data is copied in and out of storage
 476 // so that the currently executing thread always has its own copy of this
 477 // data.
 478 class HandleScopeImplementer {
 479  public:
 480   explicit HandleScopeImplementer(Isolate* isolate)
 481       : isolate_(isolate),
 482         blocks_(0),
 483         entered_contexts_(0),
 484         saved_contexts_(0),
 485         spare_(NULL),
 486         call_depth_(0),
 487         last_handle_before_deferred_block_(NULL) { }
 488
 489   ~HandleScopeImplementer() {
 490     DeleteArray(spare_);
 491   }
 492
 493   // Threading support for handle data.
 494   static int ArchiveSpacePerThread();
 495   char* RestoreThread(char* from);
 496   char* ArchiveThread(char* to);
 497   void FreeThreadResources();
 498
 499   // Garbage collection support.
 500   void Iterate(v8::internal::ObjectVisitor* v);
 501   static char* Iterate(v8::internal::ObjectVisitor* v, char* data);
 502
 503
 504   inline internal::Object** GetSpareOrNewBlock();
 505   inline void DeleteExtensions(internal::Object** prev_limit);
 506
 507   inline void IncrementCallDepth() {call_depth_++;}
 508   inline void DecrementCallDepth() {call_depth_--;}
 509   inline bool CallDepthIsZero() { return call_depth_ == 0; }
 510
 511   inline void EnterContext(Handle<Object> context);
 512   inline bool LeaveLastContext();
 513
 514   // Returns the last entered context or an empty handle if no
 515   // contexts have been entered.
 516   inline Handle<Object> LastEnteredContext();
 517
 518   inline void SaveContext(Context* context);
 519   inline Context* RestoreContext();
 520   inline bool HasSavedContexts();
 521
 522   inline List<internal::Object**>* blocks() { return &blocks_; }
 523   Isolate* isolate() const { return isolate_; }
 524
 525   void ReturnBlock(Object** block) {
 526     ASSERT(block != NULL);
 527     if (spare_ != NULL) DeleteArray(spare_);
 528     spare_ = block;
 529   }
 530
 531  private:
 532   void ResetAfterArchive() {
 533     blocks_.Initialize(0);
 534     entered_contexts_.Initialize(0);
 535     saved_contexts_.Initialize(0);
 536     spare_ = NULL;
 537     last_handle_before_deferred_block_ = NULL;
 538     call_depth_ = 0;
 539   }
 540
 541   void Free() {
 542     ASSERT(blocks_.length() == 0);
 543     ASSERT(entered_contexts_.length() == 0);
 544     ASSERT(saved_contexts_.length() == 0);
 545     blocks_.Free();
 546     entered_contexts_.Free();
 547     saved_contexts_.Free();
 548     if (spare_ != NULL) {
 549       DeleteArray(spare_);
 550       spare_ = NULL;
 551     }
 552     ASSERT(call_depth_ == 0);
 553   }
 554
 555   void BeginDeferredScope();
 556   DeferredHandles* Detach(Object** prev_limit);
 557
 558   Isolate* isolate_;
 559   List<internal::Object**> blocks_;
 560   // Used as a stack to keep track of entered contexts.
 561   List<Handle<Object> > entered_contexts_;
 562   // Used as a stack to keep track of saved contexts.
 563   List<Context*> saved_contexts_;
 564   Object** spare_;
 565   int call_depth_;
 566   Object** last_handle_before_deferred_block_;
 567   // This is only used for threading support.
 568   v8::ImplementationUtilities::HandleScopeData handle_scope_data_;
 569
 570   void IterateThis(ObjectVisitor* v);
 571   char* RestoreThreadHelper(char* from);
 572   char* ArchiveThreadHelper(char* to);
 573
 574   friend class DeferredHandles;
 575   friend class DeferredHandleScope;
 576
 577   DISALLOW_COPY_AND_ASSIGN(HandleScopeImplementer);
 578 };
 579
 580
 581 const int kHandleBlockSize = v8::internal::KB - 2;  // fit in one page
 582
 583
 584 void HandleScopeImplementer::SaveContext(Context* context) {
 585   saved_contexts_.Add(context);
 586 }
 587
 588
 589 Context* HandleScopeImplementer::RestoreContext() {
 590   return saved_contexts_.RemoveLast();
 591 }
 592
 593
 594 bool HandleScopeImplementer::HasSavedContexts() {
 595   return !saved_contexts_.is_empty();
 596 }
 597
 598
 599 void HandleScopeImplementer::EnterContext(Handle<Object> context) {
 600   entered_contexts_.Add(context);
 601 }
 602
 603
 604 bool HandleScopeImplementer::LeaveLastContext() {
 605   if (entered_contexts_.is_empty()) return false;
 606   entered_contexts_.RemoveLast();
 607   return true;
 608 }
 609
 610
 611 Handle<Object> HandleScopeImplementer::LastEnteredContext() {
 612   if (entered_contexts_.is_empty()) return Handle<Object>::null();
 613   return entered_contexts_.last();
 614 }
 615
 616
 617 // If there's a spare block, use it for growing the current scope.
 618 internal::Object** HandleScopeImplementer::GetSpareOrNewBlock() {
 619   internal::Object** block = (spare_ != NULL) ?
 620       spare_ :
 621       NewArray<internal::Object*>(kHandleBlockSize);
 622   spare_ = NULL;
 623   return block;
 624 }
 625
 626
 627 void HandleScopeImplementer::DeleteExtensions(internal::Object** prev_limit) {
 628   while (!blocks_.is_empty()) {
 629     internal::Object** block_start = blocks_.last();
 630     internal::Object** block_limit = block_start + kHandleBlockSize;
 631 #ifdef DEBUG
 632     // NoHandleAllocation may make the prev_limit to point inside the block.
 633     if (block_start <= prev_limit && prev_limit <= block_limit) break;
 634 #else
 635     if (prev_limit == block_limit) break;
 636 #endif
 637
 638     blocks_.RemoveLast();
 639 #ifdef ENABLE_EXTRA_CHECKS
 640     internal::HandleScope::ZapRange(block_start, block_limit);
 641 #endif
 642     if (spare_ != NULL) {
 643       DeleteArray(spare_);
 644     }
 645     spare_ = block_start;
 646   }
 647   ASSERT((blocks_.is_empty() && prev_limit == NULL) ||
 648          (!blocks_.is_empty() && prev_limit != NULL));
 649 }
 650
 651
 652 class Testing {
 653  public:
 654   static v8::Testing::StressType stress_type() { return stress_type_; }
 655   static void set_stress_type(v8::Testing::StressType stress_type) {
 656     stress_type_ = stress_type;
 657   }
 658
 659  private:
 660   static v8::Testing::StressType stress_type_;
 661 };
 662
 663 } }  // namespace v8::internal
 664
 665 #endif  // V8_API_H_