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// Copyright 2021 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef INCLUDE_V8_FUNCTION_CALLBACK_H_
#define INCLUDE_V8_FUNCTION_CALLBACK_H_
#include <cstdint>
#include <limits>
#include "v8-local-handle.h" // NOLINT(build/include_directory)
#include "v8-primitive.h" // NOLINT(build/include_directory)
#include "v8config.h" // NOLINT(build/include_directory)
namespace v8 {
template <typename T>
class BasicTracedReference;
template <typename T>
class Global;
class Object;
class Value;
namespace internal {
class FunctionCallbackArguments;
class PropertyCallbackArguments;
class Builtins;
} // namespace internal
namespace debug {
class ConsoleCallArguments;
} // namespace debug
template <typename T>
class ReturnValue {
public:
template <class S>
V8_INLINE ReturnValue(const ReturnValue<S>& that) : value_(that.value_) {
static_assert(std::is_base_of<T, S>::value, "type check");
}
// Local setters
template <typename S>
V8_INLINE void Set(const Global<S>& handle);
template <typename S>
V8_INLINE void SetNonEmpty(const Global<S>& handle);
template <typename S>
V8_INLINE void Set(const BasicTracedReference<S>& handle);
template <typename S>
V8_INLINE void SetNonEmpty(const BasicTracedReference<S>& handle);
template <typename S>
V8_INLINE void Set(const Local<S> handle);
template <typename S>
V8_INLINE void SetNonEmpty(const Local<S> handle);
// Fast primitive setters
V8_INLINE void Set(bool value);
V8_INLINE void Set(double i);
V8_INLINE void Set(int32_t i);
V8_INLINE void Set(uint32_t i);
V8_INLINE void Set(uint16_t);
// Fast JS primitive setters
V8_INLINE void SetNull();
V8_INLINE void SetUndefined();
V8_INLINE void SetEmptyString();
// Convenience getter for Isolate
V8_INLINE Isolate* GetIsolate() const;
// Pointer setter: Uncompilable to prevent inadvertent misuse.
template <typename S>
V8_INLINE void Set(S* whatever);
// Getter. Creates a new Local<> so it comes with a certain performance
// hit. If the ReturnValue was not yet set, this will return the undefined
// value.
V8_INLINE Local<Value> Get() const;
private:
template <class F>
friend class ReturnValue;
template <class F>
friend class FunctionCallbackInfo;
template <class F>
friend class PropertyCallbackInfo;
template <class F, class G, class H>
friend class PersistentValueMapBase;
V8_INLINE void SetInternal(internal::Address value);
// Setting the hole value has different meanings depending on the usage:
// - for function template callbacks it means that the callback returns
// the undefined value,
// - for property getter callbacks is means that the callback returns
// the undefined value (for property setter callbacks the value returned
// is ignored),
// - for interceptor callbacks it means that the request was not handled.
V8_INLINE void SetTheHole();
V8_INLINE explicit ReturnValue(internal::Address* slot);
// See FunctionCallbackInfo.
static constexpr int kIsolateValueIndex = -2;
internal::Address* value_;
};
/**
* The argument information given to function call callbacks. This
* class provides access to information about the context of the call,
* including the receiver, the number and values of arguments, and
* the holder of the function.
*/
template <typename T>
class FunctionCallbackInfo {
public:
/** The number of available arguments. */
V8_INLINE int Length() const;
/**
* Accessor for the available arguments. Returns `undefined` if the index
* is out of bounds.
*/
V8_INLINE Local<Value> operator[](int i) const;
/** Returns the receiver. This corresponds to the "this" value. */
V8_INLINE Local<Object> This() const;
/**
* If the callback was created without a Signature, this is the same
* value as This(). If there is a signature, and the signature didn't match
* This() but one of its hidden prototypes, this will be the respective
* hidden prototype.
*
* Note that this is not the prototype of This() on which the accessor
* referencing this callback was found (which in V8 internally is often
* referred to as holder [sic]).
*/
V8_INLINE Local<Object> Holder() const;
/** For construct calls, this returns the "new.target" value. */
V8_INLINE Local<Value> NewTarget() const;
/** Indicates whether this is a regular call or a construct call. */
V8_INLINE bool IsConstructCall() const;
/** The data argument specified when creating the callback. */
V8_INLINE Local<Value> Data() const;
/** The current Isolate. */
V8_INLINE Isolate* GetIsolate() const;
/** The ReturnValue for the call. */
V8_INLINE ReturnValue<T> GetReturnValue() const;
private:
friend class internal::FunctionCallbackArguments;
friend class internal::CustomArguments<FunctionCallbackInfo>;
friend class debug::ConsoleCallArguments;
static constexpr int kHolderIndex = 0;
static constexpr int kIsolateIndex = 1;
static constexpr int kUnusedIndex = 2;
static constexpr int kReturnValueIndex = 3;
static constexpr int kDataIndex = 4;
static constexpr int kNewTargetIndex = 5;
static constexpr int kArgsLength = 6;
static constexpr int kArgsLengthWithReceiver = kArgsLength + 1;
// Codegen constants:
static constexpr int kSize = 3 * internal::kApiSystemPointerSize;
static constexpr int kImplicitArgsOffset = 0;
static constexpr int kValuesOffset =
kImplicitArgsOffset + internal::kApiSystemPointerSize;
static constexpr int kLengthOffset =
kValuesOffset + internal::kApiSystemPointerSize;
static constexpr int kThisValuesIndex = -1;
static_assert(ReturnValue<Value>::kIsolateValueIndex ==
kIsolateIndex - kReturnValueIndex);
V8_INLINE FunctionCallbackInfo(internal::Address* implicit_args,
internal::Address* values, int length);
internal::Address* implicit_args_;
internal::Address* values_;
int length_;
};
/**
* The information passed to a property callback about the context
* of the property access.
*/
template <typename T>
class PropertyCallbackInfo {
public:
/**
* \return The isolate of the property access.
*/
V8_INLINE Isolate* GetIsolate() const;
/**
* \return The data set in the configuration, i.e., in
* `NamedPropertyHandlerConfiguration` or
* `IndexedPropertyHandlerConfiguration.`
*/
V8_INLINE Local<Value> Data() const;
/**
* \return The receiver. In many cases, this is the object on which the
* property access was intercepted. When using
* `Reflect.get`, `Function.prototype.call`, or similar functions, it is the
* object passed in as receiver or thisArg.
*
* \code
* void GetterCallback(Local<Name> name,
* const v8::PropertyCallbackInfo<v8::Value>& info) {
* auto context = info.GetIsolate()->GetCurrentContext();
*
* v8::Local<v8::Value> a_this =
* info.This()
* ->GetRealNamedProperty(context, v8_str("a"))
* .ToLocalChecked();
* v8::Local<v8::Value> a_holder =
* info.Holder()
* ->GetRealNamedProperty(context, v8_str("a"))
* .ToLocalChecked();
*
* CHECK(v8_str("r")->Equals(context, a_this).FromJust());
* CHECK(v8_str("obj")->Equals(context, a_holder).FromJust());
*
* info.GetReturnValue().Set(name);
* }
*
* v8::Local<v8::FunctionTemplate> templ =
* v8::FunctionTemplate::New(isolate);
* templ->InstanceTemplate()->SetHandler(
* v8::NamedPropertyHandlerConfiguration(GetterCallback));
* LocalContext env;
* env->Global()
* ->Set(env.local(), v8_str("obj"), templ->GetFunction(env.local())
* .ToLocalChecked()
* ->NewInstance(env.local())
* .ToLocalChecked())
* .FromJust();
*
* CompileRun("obj.a = 'obj'; var r = {a: 'r'}; Reflect.get(obj, 'x', r)");
* \endcode
*/
V8_INLINE Local<Object> This() const;
/**
* \return The object in the prototype chain of the receiver that has the
* interceptor. Suppose you have `x` and its prototype is `y`, and `y`
* has an interceptor. Then `info.This()` is `x` and `info.Holder()` is `y`.
* The Holder() could be a hidden object (the global object, rather
* than the global proxy).
*
* \note For security reasons, do not pass the object back into the runtime.
*/
V8_INLINE Local<Object> Holder() const;
/**
* \return The return value of the callback.
* Can be changed by calling Set().
* \code
* info.GetReturnValue().Set(...)
* \endcode
*
*/
V8_INLINE ReturnValue<T> GetReturnValue() const;
/**
* \return True if the intercepted function should throw if an error occurs.
* Usually, `true` corresponds to `'use strict'`.
*
* \note Always `false` when intercepting `Reflect.set()`
* independent of the language mode.
*/
V8_INLINE bool ShouldThrowOnError() const;
private:
friend class MacroAssembler;
friend class internal::PropertyCallbackArguments;
friend class internal::CustomArguments<PropertyCallbackInfo>;
static constexpr int kShouldThrowOnErrorIndex = 0;
static constexpr int kHolderIndex = 1;
static constexpr int kIsolateIndex = 2;
static constexpr int kUnusedIndex = 3;
static constexpr int kReturnValueIndex = 4;
static constexpr int kDataIndex = 5;
static constexpr int kThisIndex = 6;
static constexpr int kArgsLength = 7;
static constexpr int kSize = 1 * internal::kApiSystemPointerSize;
V8_INLINE explicit PropertyCallbackInfo(internal::Address* args)
: args_(args) {}
internal::Address* args_;
};
using FunctionCallback = void (*)(const FunctionCallbackInfo<Value>& info);
// --- Implementation ---
template <typename T>
ReturnValue<T>::ReturnValue(internal::Address* slot) : value_(slot) {}
template <typename T>
void ReturnValue<T>::SetInternal(internal::Address value) {
#if V8_STATIC_ROOTS_BOOL
using I = internal::Internals;
// Ensure that the upper 32-bits are not modified. Compiler should be
// able to optimize this to a store of a lower 32-bits of the value.
// This is fine since the callback can return only JavaScript values which
// are either Smis or heap objects allocated in the main cage.
*value_ = I::DecompressTaggedField(*value_, I::CompressTagged(value));
#else
*value_ = value;
#endif // V8_STATIC_ROOTS_BOOL
}
template <typename T>
template <typename S>
void ReturnValue<T>::Set(const Global<S>& handle) {
static_assert(std::is_base_of<T, S>::value, "type check");
if (V8_UNLIKELY(handle.IsEmpty())) {
SetTheHole();
} else {
SetInternal(handle.ptr());
}
}
template <typename T>
template <typename S>
void ReturnValue<T>::SetNonEmpty(const Global<S>& handle) {
static_assert(std::is_base_of<T, S>::value, "type check");
#ifdef V8_ENABLE_CHECKS
internal::VerifyHandleIsNonEmpty(handle.IsEmpty());
#endif // V8_ENABLE_CHECKS
SetInternal(handle.ptr());
}
template <typename T>
template <typename S>
void ReturnValue<T>::Set(const BasicTracedReference<S>& handle) {
static_assert(std::is_base_of<T, S>::value, "type check");
if (V8_UNLIKELY(handle.IsEmpty())) {
SetTheHole();
} else {
SetInternal(handle.ptr());
}
}
template <typename T>
template <typename S>
void ReturnValue<T>::SetNonEmpty(const BasicTracedReference<S>& handle) {
static_assert(std::is_base_of<T, S>::value, "type check");
#ifdef V8_ENABLE_CHECKS
internal::VerifyHandleIsNonEmpty(handle.IsEmpty());
#endif // V8_ENABLE_CHECKS
SetInternal(handle.ptr());
}
template <typename T>
template <typename S>
void ReturnValue<T>::Set(const Local<S> handle) {
static_assert(std::is_void<T>::value || std::is_base_of<T, S>::value,
"type check");
if (V8_UNLIKELY(handle.IsEmpty())) {
SetTheHole();
} else {
SetInternal(handle.ptr());
}
}
template <typename T>
template <typename S>
void ReturnValue<T>::SetNonEmpty(const Local<S> handle) {
static_assert(std::is_void<T>::value || std::is_base_of<T, S>::value,
"type check");
#ifdef V8_ENABLE_CHECKS
internal::VerifyHandleIsNonEmpty(handle.IsEmpty());
#endif // V8_ENABLE_CHECKS
SetInternal(handle.ptr());
}
template <typename T>
void ReturnValue<T>::Set(double i) {
static_assert(std::is_base_of<T, Number>::value, "type check");
SetNonEmpty(Number::New(GetIsolate(), i));
}
template <typename T>
void ReturnValue<T>::Set(int32_t i) {
static_assert(std::is_base_of<T, Integer>::value, "type check");
using I = internal::Internals;
if (V8_LIKELY(I::IsValidSmi(i))) {
SetInternal(I::IntToSmi(i));
return;
}
SetNonEmpty(Integer::New(GetIsolate(), i));
}
template <typename T>
void ReturnValue<T>::Set(uint32_t i) {
static_assert(std::is_base_of<T, Integer>::value, "type check");
// Can't simply use INT32_MAX here for whatever reason.
bool fits_into_int32_t = (i & (1U << 31)) == 0;
if (V8_LIKELY(fits_into_int32_t)) {
Set(static_cast<int32_t>(i));
return;
}
SetNonEmpty(Integer::NewFromUnsigned(GetIsolate(), i));
}
template <typename T>
void ReturnValue<T>::Set(uint16_t i) {
static_assert(std::is_base_of<T, Integer>::value, "type check");
using I = internal::Internals;
static_assert(I::IsValidSmi(std::numeric_limits<uint16_t>::min()));
static_assert(I::IsValidSmi(std::numeric_limits<uint16_t>::max()));
SetInternal(I::IntToSmi(i));
}
template <typename T>
void ReturnValue<T>::Set(bool value) {
static_assert(std::is_base_of<T, Boolean>::value, "type check");
using I = internal::Internals;
#if V8_STATIC_ROOTS_BOOL
#ifdef V8_ENABLE_CHECKS
internal::PerformCastCheck(
internal::ValueHelper::SlotAsValue<Value, true>(value_));
#endif // V8_ENABLE_CHECKS
SetInternal(value ? I::StaticReadOnlyRoot::kTrueValue
: I::StaticReadOnlyRoot::kFalseValue);
#else
int root_index;
if (value) {
root_index = I::kTrueValueRootIndex;
} else {
root_index = I::kFalseValueRootIndex;
}
*value_ = I::GetRoot(GetIsolate(), root_index);
#endif // V8_STATIC_ROOTS_BOOL
}
template <typename T>
void ReturnValue<T>::SetTheHole() {
using I = internal::Internals;
#if V8_STATIC_ROOTS_BOOL
SetInternal(I::StaticReadOnlyRoot::kTheHoleValue);
#else
*value_ = I::GetRoot(GetIsolate(), I::kTheHoleValueRootIndex);
#endif // V8_STATIC_ROOTS_BOOL
}
template <typename T>
void ReturnValue<T>::SetNull() {
static_assert(std::is_base_of<T, Primitive>::value, "type check");
using I = internal::Internals;
#if V8_STATIC_ROOTS_BOOL
#ifdef V8_ENABLE_CHECKS
internal::PerformCastCheck(
internal::ValueHelper::SlotAsValue<Value, true>(value_));
#endif // V8_ENABLE_CHECKS
SetInternal(I::StaticReadOnlyRoot::kNullValue);
#else
*value_ = I::GetRoot(GetIsolate(), I::kNullValueRootIndex);
#endif // V8_STATIC_ROOTS_BOOL
}
template <typename T>
void ReturnValue<T>::SetUndefined() {
static_assert(std::is_base_of<T, Primitive>::value, "type check");
using I = internal::Internals;
#if V8_STATIC_ROOTS_BOOL
#ifdef V8_ENABLE_CHECKS
internal::PerformCastCheck(
internal::ValueHelper::SlotAsValue<Value, true>(value_));
#endif // V8_ENABLE_CHECKS
SetInternal(I::StaticReadOnlyRoot::kUndefinedValue);
#else
*value_ = I::GetRoot(GetIsolate(), I::kUndefinedValueRootIndex);
#endif // V8_STATIC_ROOTS_BOOL
}
template <typename T>
void ReturnValue<T>::SetEmptyString() {
static_assert(std::is_base_of<T, String>::value, "type check");
using I = internal::Internals;
#if V8_STATIC_ROOTS_BOOL
#ifdef V8_ENABLE_CHECKS
internal::PerformCastCheck(
internal::ValueHelper::SlotAsValue<Value, true>(value_));
#endif // V8_ENABLE_CHECKS
SetInternal(I::StaticReadOnlyRoot::kEmptyString);
#else
*value_ = I::GetRoot(GetIsolate(), I::kEmptyStringRootIndex);
#endif // V8_STATIC_ROOTS_BOOL
}
template <typename T>
Isolate* ReturnValue<T>::GetIsolate() const {
return *reinterpret_cast<Isolate**>(&value_[kIsolateValueIndex]);
}
template <typename T>
Local<Value> ReturnValue<T>::Get() const {
using I = internal::Internals;
#if V8_STATIC_ROOTS_BOOL
if (I::is_identical(*value_, I::StaticReadOnlyRoot::kTheHoleValue)) {
#else
if (*value_ == I::GetRoot(GetIsolate(), I::kTheHoleValueRootIndex)) {
#endif // V8_STATIC_ROOTS_BOOL
return Undefined(GetIsolate());
}
return Local<Value>::New(GetIsolate(),
internal::ValueHelper::SlotAsValue<Value>(value_));
}
template <typename T>
template <typename S>
void ReturnValue<T>::Set(S* whatever) {
static_assert(sizeof(S) < 0, "incompilable to prevent inadvertent misuse");
}
template <typename T>
FunctionCallbackInfo<T>::FunctionCallbackInfo(internal::Address* implicit_args,
internal::Address* values,
int length)
: implicit_args_(implicit_args), values_(values), length_(length) {}
template <typename T>
Local<Value> FunctionCallbackInfo<T>::operator[](int i) const {
// values_ points to the first argument (not the receiver).
if (i < 0 || length_ <= i) return Undefined(GetIsolate());
return Local<Value>::FromSlot(values_ + i);
}
template <typename T>
Local<Object> FunctionCallbackInfo<T>::This() const {
// values_ points to the first argument (not the receiver).
return Local<Object>::FromSlot(values_ + kThisValuesIndex);
}
template <typename T>
Local<Object> FunctionCallbackInfo<T>::Holder() const {
return Local<Object>::FromSlot(&implicit_args_[kHolderIndex]);
}
template <typename T>
Local<Value> FunctionCallbackInfo<T>::NewTarget() const {
return Local<Value>::FromSlot(&implicit_args_[kNewTargetIndex]);
}
template <typename T>
Local<Value> FunctionCallbackInfo<T>::Data() const {
return Local<Value>::FromSlot(&implicit_args_[kDataIndex]);
}
template <typename T>
Isolate* FunctionCallbackInfo<T>::GetIsolate() const {
return *reinterpret_cast<Isolate**>(&implicit_args_[kIsolateIndex]);
}
template <typename T>
ReturnValue<T> FunctionCallbackInfo<T>::GetReturnValue() const {
return ReturnValue<T>(&implicit_args_[kReturnValueIndex]);
}
template <typename T>
bool FunctionCallbackInfo<T>::IsConstructCall() const {
return !NewTarget()->IsUndefined();
}
template <typename T>
int FunctionCallbackInfo<T>::Length() const {
return length_;
}
template <typename T>
Isolate* PropertyCallbackInfo<T>::GetIsolate() const {
return *reinterpret_cast<Isolate**>(&args_[kIsolateIndex]);
}
template <typename T>
Local<Value> PropertyCallbackInfo<T>::Data() const {
return Local<Value>::FromSlot(&args_[kDataIndex]);
}
template <typename T>
Local<Object> PropertyCallbackInfo<T>::This() const {
return Local<Object>::FromSlot(&args_[kThisIndex]);
}
template <typename T>
Local<Object> PropertyCallbackInfo<T>::Holder() const {
return Local<Object>::FromSlot(&args_[kHolderIndex]);
}
template <typename T>
ReturnValue<T> PropertyCallbackInfo<T>::GetReturnValue() const {
return ReturnValue<T>(&args_[kReturnValueIndex]);
}
template <typename T>
bool PropertyCallbackInfo<T>::ShouldThrowOnError() const {
using I = internal::Internals;
if (args_[kShouldThrowOnErrorIndex] !=
I::IntToSmi(I::kInferShouldThrowMode)) {
return args_[kShouldThrowOnErrorIndex] != I::IntToSmi(I::kDontThrow);
}
return v8::internal::ShouldThrowOnError(
reinterpret_cast<v8::internal::Isolate*>(GetIsolate()));
}
} // namespace v8
#endif // INCLUDE_V8_FUNCTION_CALLBACK_H_