text: // Copyright 2011 the V8 project authors. All rights reserved.
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  //       notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  //       copyright notice, this list of conditions and the following
  //       disclaimer in the documentation and/or other materials provided
  //       with the distribution.
  //     * Neither the name of Google Inc. nor the names of its
  //       contributors may be used to endorse or promote products derived
  //       from this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  #ifndef V8_API_H_
  #define V8_API_H_
  
  #include "apiutils.h"
  #include "factory.h"
  
  #include "../include/v8-testing.h"
  
  namespace v8 {
  
  // Constants used in the implementation of the API.  The most natural thing
  // would usually be to place these with the classes that use them, but
  // we want to keep them out of v8.h because it is an externally
  // visible file.
  class Consts {
   public:
    enum TemplateType {
      FUNCTION_TEMPLATE = 0,
      OBJECT_TEMPLATE = 1
    };
  };
  
  
  // Utilities for working with neander-objects, primitive
  // env-independent JSObjects used by the api.
  class NeanderObject {
   public:
    explicit NeanderObject(int size);
    explicit inline NeanderObject(v8::internal::Handle<v8::internal::Object> obj);
    explicit inline NeanderObject(v8::internal::Object* obj);
    inline v8::internal::Object* get(int index);
    inline void set(int index, v8::internal::Object* value);
    inline v8::internal::Handle<v8::internal::JSObject> value() { return value_; }
    int size();
   private:
    v8::internal::Handle<v8::internal::JSObject> value_;
  };
  
  
  // Utilities for working with neander-arrays, a simple extensible
  // array abstraction built on neander-objects.
  class NeanderArray {
   public:
    NeanderArray();
    explicit inline NeanderArray(v8::internal::Handle<v8::internal::Object> obj);
    inline v8::internal::Handle<v8::internal::JSObject> value() {
      return obj_.value();
    }
  
    void add(v8::internal::Handle<v8::internal::Object> value);
  
    int length();
  
    v8::internal::Object* get(int index);
    // Change the value at an index to undefined value. If the index is
    // out of bounds, the request is ignored. Returns the old value.
    void set(int index, v8::internal::Object* value);
   private:
    NeanderObject obj_;
  };
  
  
  NeanderObject::NeanderObject(v8::internal::Handle<v8::internal::Object> obj)
      : value_(v8::internal::Handle<v8::internal::JSObject>::cast(obj)) { }
  
  
  NeanderObject::NeanderObject(v8::internal::Object* obj)
      : value_(v8::internal::Handle<v8::internal::JSObject>(
          v8::internal::JSObject::cast(obj))) { }
  
  
  NeanderArray::NeanderArray(v8::internal::Handle<v8::internal::Object> obj)
      : obj_(obj) { }
  
  
  v8::internal::Object* NeanderObject::get(int offset) {
    ASSERT(value()->HasFastElements());
    return v8::internal::FixedArray::cast(value()->elements())->get(offset);
  }
  
  
  void NeanderObject::set(int offset, v8::internal::Object* value) {
    ASSERT(value_->HasFastElements());
    v8::internal::FixedArray::cast(value_->elements())->set(offset, value);
  }
  
  
  template <typename T> inline T ToCData(v8::internal::Object* obj) {
    STATIC_ASSERT(sizeof(T) == sizeof(v8::internal::Address));
    return reinterpret_cast<T>(
        reinterpret_cast<intptr_t>(
            v8::internal::Foreign::cast(obj)->foreign_address()));
  }
  
  
  template <typename T>
  inline v8::internal::Handle<v8::internal::Object> FromCData(T obj) {
    STATIC_ASSERT(sizeof(T) == sizeof(v8::internal::Address));
    return FACTORY->NewForeign(
        reinterpret_cast<v8::internal::Address>(reinterpret_cast<intptr_t>(obj)));
  }
  
  
  class ApiFunction {
   public:
    explicit ApiFunction(v8::internal::Address addr) : addr_(addr) { }
    v8::internal::Address address() { return addr_; }
   private:
    v8::internal::Address addr_;
  };
  
  
  
  class RegisteredExtension {
   public:
    explicit RegisteredExtension(Extension* extension);
    static void Register(RegisteredExtension* that);
    Extension* extension() { return extension_; }
    RegisteredExtension* next() { return next_; }
    RegisteredExtension* next_auto() { return next_auto_; }
    static RegisteredExtension* first_extension() { return first_extension_; }
   private:
    Extension* extension_;
    RegisteredExtension* next_;
    RegisteredExtension* next_auto_;
    static RegisteredExtension* first_extension_;
  };
  
  
  class Utils {
   public:
    static bool ReportApiFailure(const char* location, const char* message);
  
    static Local<FunctionTemplate> ToFunctionTemplate(NeanderObject obj);
    static Local<ObjectTemplate> ToObjectTemplate(NeanderObject obj);
  
    static inline Local<Context> ToLocal(
        v8::internal::Handle<v8::internal::Context> obj);
    static inline Local<Value> ToLocal(
        v8::internal::Handle<v8::internal::Object> obj);
    static inline Local<Function> ToLocal(
        v8::internal::Handle<v8::internal::JSFunction> obj);
    static inline Local<String> ToLocal(
        v8::internal::Handle<v8::internal::String> obj);
    static inline Local<RegExp> ToLocal(
        v8::internal::Handle<v8::internal::JSRegExp> obj);
    static inline Local<Object> ToLocal(
        v8::internal::Handle<v8::internal::JSObject> obj);
    static inline Local<Array> ToLocal(
        v8::internal::Handle<v8::internal::JSArray> obj);
    static inline Local<External> ToLocal(
        v8::internal::Handle<v8::internal::Foreign> obj);
    static inline Local<Message> MessageToLocal(
        v8::internal::Handle<v8::internal::Object> obj);
    static inline Local<StackTrace> StackTraceToLocal(
        v8::internal::Handle<v8::internal::JSArray> obj);
    static inline Local<StackFrame> StackFrameToLocal(
        v8::internal::Handle<v8::internal::JSObject> obj);
    static inline Local<Number> NumberToLocal(
        v8::internal::Handle<v8::internal::Object> obj);
    static inline Local<Integer> IntegerToLocal(
        v8::internal::Handle<v8::internal::Object> obj);
    static inline Local<Uint32> Uint32ToLocal(
        v8::internal::Handle<v8::internal::Object> obj);
    static inline Local<FunctionTemplate> ToLocal(
        v8::internal::Handle<v8::internal::FunctionTemplateInfo> obj);
    static inline Local<ObjectTemplate> ToLocal(
        v8::internal::Handle<v8::internal::ObjectTemplateInfo> obj);
    static inline Local<Signature> ToLocal(
        v8::internal::Handle<v8::internal::SignatureInfo> obj);
    static inline Local<TypeSwitch> ToLocal(
        v8::internal::Handle<v8::internal::TypeSwitchInfo> obj);
  
    static inline v8::internal::Handle<v8::internal::TemplateInfo>
        OpenHandle(const Template* that);
    static inline v8::internal::Handle<v8::internal::FunctionTemplateInfo>
        OpenHandle(const FunctionTemplate* that);
    static inline v8::internal::Handle<v8::internal::ObjectTemplateInfo>
        OpenHandle(const ObjectTemplate* that);
    static inline v8::internal::Handle<v8::internal::Object>
        OpenHandle(const Data* data);
    static inline v8::internal::Handle<v8::internal::JSRegExp>
        OpenHandle(const RegExp* data);
    static inline v8::internal::Handle<v8::internal::JSObject>
        OpenHandle(const v8::Object* data);
    static inline v8::internal::Handle<v8::internal::JSArray>
        OpenHandle(const v8::Array* data);
    static inline v8::internal::Handle<v8::internal::String>
        OpenHandle(const String* data);
    static inline v8::internal::Handle<v8::internal::Object>
        OpenHandle(const Script* data);
    static inline v8::internal::Handle<v8::internal::JSFunction>
        OpenHandle(const Function* data);
    static inline v8::internal::Handle<v8::internal::JSObject>
        OpenHandle(const Message* message);
    static inline v8::internal::Handle<v8::internal::JSArray>
        OpenHandle(const StackTrace* stack_trace);
    static inline v8::internal::Handle<v8::internal::JSObject>
        OpenHandle(const StackFrame* stack_frame);
    static inline v8::internal::Handle<v8::internal::Context>
        OpenHandle(const v8::Context* context);
    static inline v8::internal::Handle<v8::internal::SignatureInfo>
        OpenHandle(const v8::Signature* sig);
    static inline v8::internal::Handle<v8::internal::TypeSwitchInfo>
        OpenHandle(const v8::TypeSwitch* that);
    static inline v8::internal::Handle<v8::internal::Foreign>
        OpenHandle(const v8::External* that);
  };
  
  
  template <class T>
  inline T* ToApi(v8::internal::Handle<v8::internal::Object> obj) {
    return reinterpret_cast<T*>(obj.location());
  }
  
  
  template <class T>
  v8::internal::Handle<T> v8::internal::Handle<T>::EscapeFrom(
      v8::HandleScope* scope) {
    v8::internal::Handle<T> handle;
    if (!is_null()) {
      handle = *this;
    }
    return Utils::OpenHandle(*scope->Close(Utils::ToLocal(handle)));
  }
  
  
  // Implementations of ToLocal
  
  #define MAKE_TO_LOCAL(Name, From, To)                                       \
    Local<v8::To> Utils::Name(v8::internal::Handle<v8::internal::From> obj) { \
      ASSERT(obj.is_null() || !obj->IsTheHole());                             \
      return Local<To>(reinterpret_cast<To*>(obj.location()));                \
    }
  
  MAKE_TO_LOCAL(ToLocal, Context, Context)
  MAKE_TO_LOCAL(ToLocal, Object, Value)
  MAKE_TO_LOCAL(ToLocal, JSFunction, Function)
  MAKE_TO_LOCAL(ToLocal, String, String)
  MAKE_TO_LOCAL(ToLocal, JSRegExp, RegExp)
  MAKE_TO_LOCAL(ToLocal, JSObject, Object)
  MAKE_TO_LOCAL(ToLocal, JSArray, Array)
  MAKE_TO_LOCAL(ToLocal, Foreign, External)
  MAKE_TO_LOCAL(ToLocal, FunctionTemplateInfo, FunctionTemplate)
  MAKE_TO_LOCAL(ToLocal, ObjectTemplateInfo, ObjectTemplate)
  MAKE_TO_LOCAL(ToLocal, SignatureInfo, Signature)
  MAKE_TO_LOCAL(ToLocal, TypeSwitchInfo, TypeSwitch)
  MAKE_TO_LOCAL(MessageToLocal, Object, Message)
  MAKE_TO_LOCAL(StackTraceToLocal, JSArray, StackTrace)
  MAKE_TO_LOCAL(StackFrameToLocal, JSObject, StackFrame)
  MAKE_TO_LOCAL(NumberToLocal, Object, Number)
  MAKE_TO_LOCAL(IntegerToLocal, Object, Integer)
  MAKE_TO_LOCAL(Uint32ToLocal, Object, Uint32)
  
  #undef MAKE_TO_LOCAL
  
  
  // Implementations of OpenHandle
  
  #define MAKE_OPEN_HANDLE(From, To) \
    v8::internal::Handle<v8::internal::To> Utils::OpenHandle(\
      const v8::From* that) { \
      return v8::internal::Handle<v8::internal::To>( \
          reinterpret_cast<v8::internal::To**>(const_cast<v8::From*>(that))); \
    }
  
  MAKE_OPEN_HANDLE(Template, TemplateInfo)
  MAKE_OPEN_HANDLE(FunctionTemplate, FunctionTemplateInfo)
  MAKE_OPEN_HANDLE(ObjectTemplate, ObjectTemplateInfo)
  MAKE_OPEN_HANDLE(Signature, SignatureInfo)
  MAKE_OPEN_HANDLE(TypeSwitch, TypeSwitchInfo)
  MAKE_OPEN_HANDLE(Data, Object)
  MAKE_OPEN_HANDLE(RegExp, JSRegExp)
  MAKE_OPEN_HANDLE(Object, JSObject)
  MAKE_OPEN_HANDLE(Array, JSArray)
  MAKE_OPEN_HANDLE(String, String)
  MAKE_OPEN_HANDLE(Script, Object)
  MAKE_OPEN_HANDLE(Function, JSFunction)
  MAKE_OPEN_HANDLE(Message, JSObject)
  MAKE_OPEN_HANDLE(Context, Context)
  MAKE_OPEN_HANDLE(External, Foreign)
  MAKE_OPEN_HANDLE(StackTrace, JSArray)
  MAKE_OPEN_HANDLE(StackFrame, JSObject)
  
  #undef MAKE_OPEN_HANDLE
  
  
  namespace internal {
  
  // Tracks string usage to help make better decisions when
  // externalizing strings.
  //
  // Implementation note: internally this class only tracks fresh
  // strings and keeps a single use counter for them.
  class StringTracker {
   public:
    // Records that the given string's characters were copied to some
    // external buffer. If this happens often we should honor
    // externalization requests for the string.
    void RecordWrite(Handle<String> string) {
      Address address = reinterpret_cast<Address>(*string);
      Address top = isolate_->heap()->NewSpaceTop();
      if (IsFreshString(address, top)) {
        IncrementUseCount(top);
      }
    }
  
    // Estimates freshness and use frequency of the given string based
    // on how close it is to the new space top and the recorded usage
    // history.
    inline bool IsFreshUnusedString(Handle<String> string) {
      Address address = reinterpret_cast<Address>(*string);
      Address top = isolate_->heap()->NewSpaceTop();
      return IsFreshString(address, top) && IsUseCountLow(top);
    }
  
   private:
    StringTracker() : use_count_(0), last_top_(NULL), isolate_(NULL) { }
  
    static inline bool IsFreshString(Address string, Address top) {
      return top - kFreshnessLimit <= string && string <= top;
    }
  
    inline bool IsUseCountLow(Address top) {
      if (last_top_ != top) return true;
      return use_count_ < kUseLimit;
    }
  
    inline void IncrementUseCount(Address top) {
      if (last_top_ != top) {
        use_count_ = 0;
        last_top_ = top;
      }
      ++use_count_;
    }
  
    // Single use counter shared by all fresh strings.
    int use_count_;
  
    // Last new space top when the use count above was valid.
    Address last_top_;
  
    Isolate* isolate_;
  
    // How close to the new space top a fresh string has to be.
    static const int kFreshnessLimit = 1024;
  
    // The number of uses required to consider a string useful.
    static const int kUseLimit = 32;
  
    friend class Isolate;
  
    DISALLOW_COPY_AND_ASSIGN(StringTracker);
  };
  
  
  // This class is here in order to be able to declare it a friend of
  // HandleScope.  Moving these methods to be members of HandleScope would be
  // neat in some ways, but it would expose internal implementation details in
  // our public header file, which is undesirable.
  //
  // An isolate has a single instance of this class to hold the current thread's
  // data. In multithreaded V8 programs this data is copied in and out of storage
  // so that the currently executing thread always has its own copy of this
  // data.
  class HandleScopeImplementer {
   public:
    explicit HandleScopeImplementer(Isolate* isolate)
        : isolate_(isolate),
          blocks_(0),
          entered_contexts_(0),
          saved_contexts_(0),
          spare_(NULL),
          call_depth_(0) { }
  
    ~HandleScopeImplementer() {
      DeleteArray(spare_);
    }
  
    // Threading support for handle data.
    static int ArchiveSpacePerThread();
    char* RestoreThread(char* from);
    char* ArchiveThread(char* to);
    void FreeThreadResources();
  
    // Garbage collection support.
    void Iterate(v8::internal::ObjectVisitor* v);
    static char* Iterate(v8::internal::ObjectVisitor* v, char* data);
  
  
    inline internal::Object** GetSpareOrNewBlock();
    inline void DeleteExtensions(internal::Object** prev_limit);
  
    inline void IncrementCallDepth() {call_depth_++;}
    inline void DecrementCallDepth() {call_depth_--;}
    inline bool CallDepthIsZero() { return call_depth_ == 0; }
  
    inline void EnterContext(Handle<Object> context);
    inline bool LeaveLastContext();
  
    // Returns the last entered context or an empty handle if no
    // contexts have been entered.
    inline Handle<Object> LastEnteredContext();
  
    inline void SaveContext(Context* context);
    inline Context* RestoreContext();
    inline bool HasSavedContexts();
  
    inline List<internal::Object**>* blocks() { return &blocks_; }
  
   private:
    void ResetAfterArchive() {
      blocks_.Initialize(0);
      entered_contexts_.Initialize(0);
      saved_contexts_.Initialize(0);
      spare_ = NULL;
      call_depth_ = 0;
    }
  
    void Free() {
      ASSERT(blocks_.length() == 0);
      ASSERT(entered_contexts_.length() == 0);
      ASSERT(saved_contexts_.length() == 0);
      blocks_.Free();
      entered_contexts_.Free();
      saved_contexts_.Free();
      if (spare_ != NULL) {
        DeleteArray(spare_);
        spare_ = NULL;
      }
      ASSERT(call_depth_ == 0);
    }
  
    Isolate* isolate_;
    List<internal::Object**> blocks_;
    // Used as a stack to keep track of entered contexts.
    List<Handle<Object> > entered_contexts_;
    // Used as a stack to keep track of saved contexts.
    List<Context*> saved_contexts_;
    Object** spare_;
    int call_depth_;
    // This is only used for threading support.
    v8::ImplementationUtilities::HandleScopeData handle_scope_data_;
  
    void IterateThis(ObjectVisitor* v);
    char* RestoreThreadHelper(char* from);
    char* ArchiveThreadHelper(char* to);
  
    DISALLOW_COPY_AND_ASSIGN(HandleScopeImplementer);
  };
  
  
  const int kHandleBlockSize = v8::internal::KB - 2;  // fit in one page
  
  
  void HandleScopeImplementer::SaveContext(Context* context) {
    saved_contexts_.Add(context);
  }
  
  
  Context* HandleScopeImplementer::RestoreContext() {
    return saved_contexts_.RemoveLast();
  }
  
  
  bool HandleScopeImplementer::HasSavedContexts() {
    return !saved_contexts_.is_empty();
  }
  
  
  void HandleScopeImplementer::EnterContext(Handle<Object> context) {
    entered_contexts_.Add(context);
  }
  
  
  bool HandleScopeImplementer::LeaveLastContext() {
    if (entered_contexts_.is_empty()) return false;
    entered_contexts_.RemoveLast();
    return true;
  }
  
  
  Handle<Object> HandleScopeImplementer::LastEnteredContext() {
    if (entered_contexts_.is_empty()) return Handle<Object>::null();
    return entered_contexts_.last();
  }
  
  
  // If there's a spare block, use it for growing the current scope.
  internal::Object** HandleScopeImplementer::GetSpareOrNewBlock() {
    internal::Object** block = (spare_ != NULL) ?
        spare_ :
        NewArray<internal::Object*>(kHandleBlockSize);
    spare_ = NULL;
    return block;
  }
  
  
  void HandleScopeImplementer::DeleteExtensions(internal::Object** prev_limit) {
    while (!blocks_.is_empty()) {
      internal::Object** block_start = blocks_.last();
      internal::Object** block_limit = block_start + kHandleBlockSize;
  #ifdef DEBUG
      // NoHandleAllocation may make the prev_limit to point inside the block.
      if (block_start <= prev_limit && prev_limit <= block_limit) break;
  #else
      if (prev_limit == block_limit) break;
  #endif
  
      blocks_.RemoveLast();
  #ifdef DEBUG
      v8::ImplementationUtilities::ZapHandleRange(block_start, block_limit);
  #endif
      if (spare_ != NULL) {
        DeleteArray(spare_);
      }
      spare_ = block_start;
    }
    ASSERT((blocks_.is_empty() && prev_limit == NULL) ||
           (!blocks_.is_empty() && prev_limit != NULL));
  }
  
  
  class Testing {
   public:
    static v8::Testing::StressType stress_type() { return stress_type_; }
    static void set_stress_type(v8::Testing::StressType stress_type) {
      stress_type_ = stress_type;
    }
  
   private:
    static v8::Testing::StressType stress_type_;
  };
  
  } }  // namespace v8::internal
  
  #endif  // V8_API_H_
  