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