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v8::Context Class Reference

#include <v8-context.h>

Inheritance diagram for v8::Context:
Collaboration diagram for v8::Context:


class  BackupIncumbentScope
class  DeepFreezeDelegate
class  Scope

Public Types

enum  EmbedderDataFields { kDebugIdIndex = 0 }
using AbortScriptExecutionCallback = void(*)(Isolate *isolate, Local< Context > context)

Public Member Functions

Local< ObjectGlobal ()
void DetachGlobal ()
void SetSecurityToken (Local< Value > token)
void UseDefaultSecurityToken ()
Local< ValueGetSecurityToken ()
void Enter ()
void Exit ()
Maybe< void > DeepFreeze (DeepFreezeDelegate *delegate=nullptr)
IsolateGetIsolate ()
MicrotaskQueueGetMicrotaskQueue ()
void SetMicrotaskQueue (MicrotaskQueue *queue)
uint32_t GetNumberOfEmbedderDataFields ()
Local< ValueGetEmbedderData (int index)
Local< ObjectGetExtrasBindingObject ()
void SetEmbedderData (int index, Local< Value > value)
void * GetAlignedPointerFromEmbedderData (int index)
void SetAlignedPointerInEmbedderData (int index, void *value)
void AllowCodeGenerationFromStrings (bool allow)
bool IsCodeGenerationFromStringsAllowed () const
void SetErrorMessageForCodeGenerationFromStrings (Local< String > message)
void SetErrorMessageForWasmCodeGeneration (Local< String > message)
template<class T >
MaybeLocal< T > GetDataFromSnapshotOnce (size_t index)
void SetAbortScriptExecution (AbortScriptExecutionCallback callback)
Local< ValueGetContinuationPreservedEmbedderData () const
void SetContinuationPreservedEmbedderData (Local< Value > context)
void SetPromiseHooks (Local< Function > init_hook, Local< Function > before_hook, Local< Function > after_hook, Local< Function > resolve_hook)
bool HasTemplateLiteralObject (Local< Value > object)
- Public Member Functions inherited from v8::Data
bool IsValue () const
bool IsModule () const
bool IsFixedArray () const
bool IsPrivate () const
bool IsObjectTemplate () const
bool IsFunctionTemplate () const
bool IsContext () const

Static Public Member Functions

static Local< ContextNew (Isolate *isolate, ExtensionConfiguration *extensions=nullptr, MaybeLocal< ObjectTemplate > global_template=MaybeLocal< ObjectTemplate >(), MaybeLocal< Value > global_object=MaybeLocal< Value >(), DeserializeInternalFieldsCallback internal_fields_deserializer=DeserializeInternalFieldsCallback(), MicrotaskQueue *microtask_queue=nullptr)
static MaybeLocal< ContextFromSnapshot (Isolate *isolate, size_t context_snapshot_index, DeserializeInternalFieldsCallback embedder_fields_deserializer=DeserializeInternalFieldsCallback(), ExtensionConfiguration *extensions=nullptr, MaybeLocal< Value > global_object=MaybeLocal< Value >(), MicrotaskQueue *microtask_queue=nullptr)
static MaybeLocal< ObjectNewRemoteContext (Isolate *isolate, Local< ObjectTemplate > global_template, MaybeLocal< Value > global_object=MaybeLocal< Value >())
static ContextCast (Data *data)


class Value
class Script
class Object
class Function

Detailed Description

A sandboxed execution context with its own set of built-in objects and functions.


Member Typedef Documentation

◆ AbortScriptExecutionCallback

using v8::Context::AbortScriptExecutionCallback = void (*)(Isolate* isolate, Local<Context> context)

If callback is set, abort any attempt to execute JavaScript in this context, call the specified callback, and throw an exception. To unset abort, pass nullptr as callback.

Member Enumeration Documentation

◆ EmbedderDataFields

The field at kDebugIdIndex used to be reserved for the inspector. It now serves no purpose.


Member Function Documentation

◆ AllowCodeGenerationFromStrings()

void v8::Context::AllowCodeGenerationFromStrings ( bool  allow)

Control whether code generation from strings is allowed. Calling this method with false will disable 'eval' and the 'Function' constructor for code running in this context. If 'eval' or the 'Function' constructor are used an exception will be thrown.

If code generation from strings is not allowed the V8::AllowCodeGenerationFromStrings callback will be invoked if set before blocking the call to 'eval' or the 'Function' constructor. If that callback returns true, the call will be allowed, otherwise an exception will be thrown. If no callback is set an exception will be thrown.

◆ Cast()

Context * v8::Context::Cast ( v8::Data data)

◆ DeepFreeze()

Maybe< void > v8::Context::DeepFreeze ( DeepFreezeDelegate delegate = nullptr)

Attempts to recursively freeze all objects reachable from this context. Some objects (generators, iterators, non-const closures) can not be frozen and will cause this method to throw an error. An optional delegate can be provided to help freeze embedder-specific objects.

Freezing occurs in two steps:

  1. "Marking" where we iterate through all objects reachable by this context, accumulating a list of objects that need to be frozen and looking for objects that can't be frozen. This step is separated because it is more efficient when we can assume there is no garbage collection.
  2. "Freezing" where we go through the list of objects and freezing them. This effectively requires copying them so it may trigger garbage collection.

◆ DetachGlobal()

void v8::Context::DetachGlobal ( )

Detaches the global object from its context before the global object can be reused to create a new context.

◆ Enter()

void v8::Context::Enter ( )

Enter this context. After entering a context, all code compiled and run is compiled and run in this context. If another context is already entered, this old context is saved so it can be restored when the new context is exited.

◆ Exit()

void v8::Context::Exit ( )

Exit this context. Exiting the current context restores the context that was in place when entering the current context.

◆ FromSnapshot()

static MaybeLocal< Context > v8::Context::FromSnapshot ( Isolate isolate,
size_t  context_snapshot_index,
DeserializeInternalFieldsCallback  embedder_fields_deserializer = DeserializeInternalFieldsCallback(),
ExtensionConfiguration extensions = nullptr,
MaybeLocal< Value global_object = MaybeLocalValue >(),
MicrotaskQueue microtask_queue = nullptr 

Create a new context from a (non-default) context snapshot. There is no way to provide a global object template since we do not create a new global object from template, but we can reuse a global object.

isolateSee v8::Context::New.
context_snapshot_indexThe index of the context snapshot to deserialize from. Use v8::Context::New for the default snapshot.
embedder_fields_deserializerOptional callback to deserialize internal fields. It should match the SerializeInternalFieldCallback used to serialize.
extensionsSee v8::Context::New.
global_objectSee v8::Context::New.

◆ GetAlignedPointerFromEmbedderData()

void * v8::Context::GetAlignedPointerFromEmbedderData ( int  index)

Gets a 2-byte-aligned native pointer from the embedder data with the given index, which must have been set by a previous call to SetAlignedPointerInEmbedderData with the same index. Note that index 0 currently has a special meaning for Chrome's debugger.

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◆ GetContinuationPreservedEmbedderData()

Local< Value > v8::Context::GetContinuationPreservedEmbedderData ( ) const

Returns the value that was set or restored by SetContinuationPreservedEmbedderData(), if any.

◆ GetDataFromSnapshotOnce()

template<class T >
MaybeLocal< T > v8::Context::GetDataFromSnapshotOnce ( size_t  index)

Return data that was previously attached to the context snapshot via SnapshotCreator, and removes the reference to it. Repeated call with the same index returns an empty MaybeLocal.

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◆ GetEmbedderData()

Local< Value > v8::Context::GetEmbedderData ( int  index)

Gets the embedder data with the given index, which must have been set by a previous call to SetEmbedderData with the same index.

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◆ GetExtrasBindingObject()

Local< Object > v8::Context::GetExtrasBindingObject ( )

Gets the binding object used by V8 extras. Extra natives get a reference to this object and can use it to "export" functionality by adding properties. Extra natives can also "import" functionality by accessing properties added by the embedder using the V8 API.

◆ GetIsolate()

Isolate * v8::Context::GetIsolate ( )

Returns the isolate associated with a current context.

◆ GetMicrotaskQueue()

MicrotaskQueue * v8::Context::GetMicrotaskQueue ( )

Returns the microtask queue associated with a current context.

◆ GetNumberOfEmbedderDataFields()

uint32_t v8::Context::GetNumberOfEmbedderDataFields ( )

Return the number of fields allocated for embedder data.

◆ GetSecurityToken()

Local< Value > v8::Context::GetSecurityToken ( )

Returns the security token of this context.

◆ Global()

Local< Object > v8::Context::Global ( )

Returns the global proxy object.

Global proxy object is a thin wrapper whose prototype points to actual context's global object with the properties like Object, etc. This is done that way for security reasons (for more details see https://wiki.mozilla.org/Gecko:SplitWindow).

Please note that changes to global proxy object prototype most probably would break VM—v8 expects only global object as a prototype of global proxy object.

◆ HasTemplateLiteralObject()

bool v8::Context::HasTemplateLiteralObject ( Local< Value object)

◆ IsCodeGenerationFromStringsAllowed()

bool v8::Context::IsCodeGenerationFromStringsAllowed ( ) const

Returns true if code generation from strings is allowed for the context. For more details see AllowCodeGenerationFromStrings(bool) documentation.

◆ New()

static Local< Context > v8::Context::New ( Isolate isolate,
ExtensionConfiguration extensions = nullptr,
MaybeLocal< ObjectTemplate global_template = MaybeLocalObjectTemplate >(),
MaybeLocal< Value global_object = MaybeLocalValue >(),
DeserializeInternalFieldsCallback  internal_fields_deserializer = DeserializeInternalFieldsCallback(),
MicrotaskQueue microtask_queue = nullptr 

Creates a new context and returns a handle to the newly allocated context.

isolateThe isolate in which to create the context.
extensionsAn optional extension configuration containing the extensions to be installed in the newly created context.
global_templateAn optional object template from which the global object for the newly created context will be created.
global_objectAn optional global object to be reused for the newly created context. This global object must have been created by a previous call to Context::New with the same global template. The state of the global object will be completely reset and only object identify will remain.

◆ NewRemoteContext()

static MaybeLocal< Object > v8::Context::NewRemoteContext ( Isolate isolate,
Local< ObjectTemplate global_template,
MaybeLocal< Value global_object = MaybeLocalValue >() 

Returns an global object that isn't backed by an actual context.

The global template needs to have access checks with handlers installed. If an existing global object is passed in, the global object is detached from its context.

Note that this is different from a detached context where all accesses to the global proxy will fail. Instead, the access check handlers are invoked.

It is also not possible to detach an object returned by this method. Instead, the access check handlers need to return nothing to achieve the same effect.

It is possible, however, to create a new context from the global object returned by this method.

◆ SetAbortScriptExecution()

void v8::Context::SetAbortScriptExecution ( AbortScriptExecutionCallback  callback)

◆ SetAlignedPointerInEmbedderData()

void v8::Context::SetAlignedPointerInEmbedderData ( int  index,
void *  value 

Sets a 2-byte-aligned native pointer in the embedder data with the given index, growing the data as needed. Note that index 0 currently has a special meaning for Chrome's debugger.

◆ SetContinuationPreservedEmbedderData()

void v8::Context::SetContinuationPreservedEmbedderData ( Local< Value context)

Sets a value that will be stored on continuations and reset while the continuation runs.

◆ SetEmbedderData()

void v8::Context::SetEmbedderData ( int  index,
Local< Value value 

Sets the embedder data with the given index, growing the data as needed. Note that index 0 currently has a special meaning for Chrome's debugger.

◆ SetErrorMessageForCodeGenerationFromStrings()

void v8::Context::SetErrorMessageForCodeGenerationFromStrings ( Local< String message)

Sets the error description for the exception that is thrown when code generation from strings is not allowed and 'eval' or the 'Function' constructor are called.

◆ SetErrorMessageForWasmCodeGeneration()

void v8::Context::SetErrorMessageForWasmCodeGeneration ( Local< String message)

Sets the error description for the exception that is thrown when wasm code generation is not allowed.

◆ SetMicrotaskQueue()

void v8::Context::SetMicrotaskQueue ( MicrotaskQueue queue)

Sets the microtask queue associated with the current context.

◆ SetPromiseHooks()

void v8::Context::SetPromiseHooks ( Local< Function init_hook,
Local< Function before_hook,
Local< Function after_hook,
Local< Function resolve_hook 

Set or clear hooks to be invoked for promise lifecycle operations. To clear a hook, set it to an empty v8::Function. Each function will receive the observed promise as the first argument. If a chaining operation is used on a promise, the init will additionally receive the parent promise as the second argument.

◆ SetSecurityToken()

void v8::Context::SetSecurityToken ( Local< Value token)

Sets the security token for the context. To access an object in another context, the security tokens must match.

◆ UseDefaultSecurityToken()

void v8::Context::UseDefaultSecurityToken ( )

Restores the security token to the default value.

Friends And Related Function Documentation

◆ Function

friend class Function

◆ Object

friend class Object

◆ Script

friend class Script

◆ Value

friend class Value

The documentation for this class was generated from the following file: