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gecko-dev/js/public/Class.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sts=4 et sw=4 tw=99:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* JSClass definition and its component types, plus related interfaces. */
#ifndef js_Class_h
#define js_Class_h
#include "jstypes.h"
#include "js/CallArgs.h"
#include "js/Id.h"
#include "js/TypeDecls.h"
/*
* A JSClass acts as a vtable for JS objects that allows JSAPI clients to
* control various aspects of the behavior of an object like property lookup.
* js::Class is an engine-private extension that allows more control over
* object behavior and, e.g., allows custom slow layout.
*/
struct JSAtomState;
struct JSFreeOp;
struct JSFunctionSpec;
namespace js {
struct Class;
class FreeOp;
class Shape;
// This is equal to JSFunction::class_. Use it in places where you don't want
// to #include jsfun.h.
extern JS_FRIEND_DATA(const js::Class* const) FunctionClassPtr;
} // namespace js
namespace JS {
/**
* The answer to a successful query as to whether an object is an Array per
* ES6's internal |IsArray| operation (as exposed by |Array.isArray|).
*/
enum class IsArrayAnswer
{
Array,
NotArray,
RevokedProxy
};
/**
* ES6 7.2.2.
*
* Returns false on failure, otherwise returns true and sets |*isArray|
* indicating whether the object passes ECMAScript's IsArray test. This is the
* same test performed by |Array.isArray|.
*
* This is NOT the same as asking whether |obj| is an Array or a wrapper around
* one. If |obj| is a proxy created by |Proxy.revocable()| and has been
* revoked, or if |obj| is a proxy whose target (at any number of hops) is a
* revoked proxy, this method throws a TypeError and returns false.
*/
extern JS_PUBLIC_API(bool)
IsArray(JSContext* cx, HandleObject obj, bool* isArray);
/**
* Identical to IsArray above, but the nature of the object (if successfully
* determined) is communicated via |*answer|. In particular this method
* returns true and sets |*answer = IsArrayAnswer::RevokedProxy| when called on
* a revoked proxy.
*
* Most users will want the overload above, not this one.
*/
extern JS_PUBLIC_API(bool)
IsArray(JSContext* cx, HandleObject obj, IsArrayAnswer* answer);
/**
* Per ES6, the [[DefineOwnProperty]] internal method has three different
* possible outcomes:
*
* - It can throw an exception (which we indicate by returning false).
*
* - It can return true, indicating unvarnished success.
*
* - It can return false, indicating "strict failure". The property could
* not be defined. It's an error, but no exception was thrown.
*
* It's not just [[DefineOwnProperty]]: all the mutating internal methods have
* the same three outcomes. (The other affected internal methods are [[Set]],
* [[Delete]], [[SetPrototypeOf]], and [[PreventExtensions]].)
*
* If you think this design is awful, you're not alone. But as it's the
* standard, we must represent these boolean "success" values somehow.
* ObjectOpSuccess is the class for this. It's like a bool, but when it's false
* it also stores an error code.
*
* Typical usage:
*
* ObjectOpResult result;
* if (!DefineProperty(cx, obj, id, ..., result))
* return false;
* if (!result)
* return result.reportError(cx, obj, id);
*
* Users don't have to call `result.report()`; another possible ending is:
*
* argv.rval().setBoolean(bool(result));
* return true;
*/
class ObjectOpResult
{
private:
/**
* code_ is either one of the special codes OkCode or Uninitialized, or
* an error code. For now the error codes are private to the JS engine;
* they're defined in js/src/js.msg.
*
* code_ is uintptr_t (rather than uint32_t) for the convenience of the
* JITs, which would otherwise have to deal with either padding or stack
* alignment on 64-bit platforms.
*/
uintptr_t code_;
public:
enum SpecialCodes : uintptr_t {
OkCode = 0,
Uninitialized = uintptr_t(-1)
};
ObjectOpResult() : code_(Uninitialized) {}
/* Return true if succeed() was called. */
bool ok() const {
MOZ_ASSERT(code_ != Uninitialized);
return code_ == OkCode;
}
explicit operator bool() const { return ok(); }
/* Set this ObjectOpResult to true and return true. */
bool succeed() {
code_ = OkCode;
return true;
}
/*
* Set this ObjectOpResult to false with an error code.
*
* Always returns true, as a convenience. Typical usage will be:
*
* if (funny condition)
* return result.fail(JSMSG_CANT_DO_THE_THINGS);
*
* The true return value indicates that no exception is pending, and it
* would be OK to ignore the failure and continue.
*/
bool fail(uint32_t msg) {
MOZ_ASSERT(msg != OkCode);
code_ = msg;
return true;
}
JS_PUBLIC_API(bool) failCantRedefineProp();
JS_PUBLIC_API(bool) failReadOnly();
JS_PUBLIC_API(bool) failGetterOnly();
JS_PUBLIC_API(bool) failCantDelete();
JS_PUBLIC_API(bool) failCantSetInterposed();
JS_PUBLIC_API(bool) failCantDefineWindowElement();
JS_PUBLIC_API(bool) failCantDeleteWindowElement();
JS_PUBLIC_API(bool) failCantDeleteWindowNamedProperty();
JS_PUBLIC_API(bool) failCantPreventExtensions();
JS_PUBLIC_API(bool) failCantSetProto();
JS_PUBLIC_API(bool) failNoNamedSetter();
JS_PUBLIC_API(bool) failNoIndexedSetter();
uint32_t failureCode() const {
MOZ_ASSERT(!ok());
return uint32_t(code_);
}
/*
* Report an error or warning if necessary; return true to proceed and
* false if an error was reported. Call this when failure should cause
* a warning if extraWarnings are enabled.
*
* The precise rules are like this:
*
* - If ok(), then we succeeded. Do nothing and return true.
* - Otherwise, if |strict| is true, or if cx has both extraWarnings and
* werrorOption enabled, throw a TypeError and return false.
* - Otherwise, if cx has extraWarnings enabled, emit a warning and
* return true.
* - Otherwise, do nothing and return true.
*/
bool checkStrictErrorOrWarning(JSContext* cx, HandleObject obj, HandleId id, bool strict) {
if (ok())
return true;
return reportStrictErrorOrWarning(cx, obj, id, strict);
}
/*
* The same as checkStrictErrorOrWarning(cx, id, strict), except the
* operation is not associated with a particular property id. This is
* used for [[PreventExtensions]] and [[SetPrototypeOf]]. failureCode()
* must not be an error that has "{0}" in the error message.
*/
bool checkStrictErrorOrWarning(JSContext* cx, HandleObject obj, bool strict) {
return ok() || reportStrictErrorOrWarning(cx, obj, strict);
}
/* Throw a TypeError. Call this only if !ok(). */
bool reportError(JSContext* cx, HandleObject obj, HandleId id) {
return reportStrictErrorOrWarning(cx, obj, id, true);
}
/*
* The same as reportError(cx, obj, id), except the operation is not
* associated with a particular property id.
*/
bool reportError(JSContext* cx, HandleObject obj) {
return reportStrictErrorOrWarning(cx, obj, true);
}
/* Helper function for checkStrictErrorOrWarning's slow path. */
JS_PUBLIC_API(bool) reportStrictErrorOrWarning(JSContext* cx, HandleObject obj, HandleId id, bool strict);
JS_PUBLIC_API(bool) reportStrictErrorOrWarning(JSContext* cx, HandleObject obj, bool strict);
/*
* Convenience method. Return true if ok() or if strict is false; otherwise
* throw a TypeError and return false.
*/
bool checkStrict(JSContext* cx, HandleObject obj, HandleId id) {
return checkStrictErrorOrWarning(cx, obj, id, true);
}
/*
* Convenience method. The same as checkStrict(cx, id), except the
* operation is not associated with a particular property id.
*/
bool checkStrict(JSContext* cx, HandleObject obj) {
return checkStrictErrorOrWarning(cx, obj, true);
}
};
class PropertyResult
{
union {
js::Shape* shape_;
uintptr_t bits_;
};
static const uintptr_t NotFound = 0;
static const uintptr_t NonNativeProperty = 1;
static const uintptr_t DenseOrTypedArrayElement = 1;
public:
PropertyResult() : bits_(NotFound) {}
explicit PropertyResult(js::Shape* propertyShape)
: shape_(propertyShape)
{
MOZ_ASSERT(!isFound() || isNativeProperty());
}
explicit operator bool() const {
return isFound();
}
bool isFound() const {
return bits_ != NotFound;
}
bool isNonNativeProperty() const {
return bits_ == NonNativeProperty;
}
bool isDenseOrTypedArrayElement() const {
return bits_ == DenseOrTypedArrayElement;
}
bool isNativeProperty() const {
return isFound() && !isNonNativeProperty();
}
js::Shape* maybeShape() const {
MOZ_ASSERT(!isNonNativeProperty());
return isFound() ? shape_ : nullptr;
}
js::Shape* shape() const {
MOZ_ASSERT(isNativeProperty());
return shape_;
}
void setNotFound() {
bits_ = NotFound;
}
void setNativeProperty(js::Shape* propertyShape) {
shape_ = propertyShape;
MOZ_ASSERT(isNativeProperty());
}
void setNonNativeProperty() {
bits_ = NonNativeProperty;
}
void setDenseOrTypedArrayElement() {
bits_ = DenseOrTypedArrayElement;
}
void trace(JSTracer* trc);
};
} // namespace JS
namespace js {
template <class Wrapper>
class WrappedPtrOperations<JS::PropertyResult, Wrapper>
{
const JS::PropertyResult& value() const { return static_cast<const Wrapper*>(this)->get(); }
public:
bool isFound() const { return value().isFound(); }
explicit operator bool() const { return bool(value()); }
js::Shape* maybeShape() const { return value().maybeShape(); }
js::Shape* shape() const { return value().shape(); }
bool isNativeProperty() const { return value().isNativeProperty(); }
bool isNonNativeProperty() const { return value().isNonNativeProperty(); }
bool isDenseOrTypedArrayElement() const { return value().isDenseOrTypedArrayElement(); }
js::Shape* asTaggedShape() const { return value().asTaggedShape(); }
};
template <class Wrapper>
class MutableWrappedPtrOperations<JS::PropertyResult, Wrapper>
: public WrappedPtrOperations<JS::PropertyResult, Wrapper>
{
JS::PropertyResult& value() { return static_cast<Wrapper*>(this)->get(); }
public:
void setNotFound() {
value().setNotFound();
}
void setNativeProperty(js::Shape* shape) {
value().setNativeProperty(shape);
}
void setNonNativeProperty() {
value().setNonNativeProperty();
}
void setDenseOrTypedArrayElement() {
value().setDenseOrTypedArrayElement();
}
};
} // namespace js
// JSClass operation signatures.
/**
* Get a property named by id in obj. Note the jsid id type -- id may
* be a string (Unicode property identifier) or an int (element index). The
* *vp out parameter, on success, is the new property value after the action.
*/
typedef bool
(* JSGetterOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id,
JS::MutableHandleValue vp);
/** Add a property named by id to obj. */
typedef bool
(* JSAddPropertyOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id, JS::HandleValue v);
/**
* Set a property named by id in obj, treating the assignment as strict
* mode code if strict is true. Note the jsid id type -- id may be a string
* (Unicode property identifier) or an int (element index).
*/
typedef bool
(* JSSetterOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id,
JS::HandleValue v, JS::ObjectOpResult& result);
/**
* Delete a property named by id in obj.
*
* If an error occurred, return false as per normal JSAPI error practice.
*
* If no error occurred, but the deletion attempt wasn't allowed (perhaps
* because the property was non-configurable), call result.fail() and
* return true. This will cause |delete obj[id]| to evaluate to false in
* non-strict mode code, and to throw a TypeError in strict mode code.
*
* If no error occurred and the deletion wasn't disallowed (this is *not* the
* same as saying that a deletion actually occurred -- deleting a non-existent
* property, or an inherited property, is allowed -- it's just pointless),
* call result.succeed() and return true.
*/
typedef bool
(* JSDeletePropertyOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id,
JS::ObjectOpResult& result);
/**
* The type of ObjectOps::enumerate. This callback overrides a portion of
* SpiderMonkey's default [[Enumerate]] internal method. When an ordinary object
* is enumerated, that object and each object on its prototype chain is tested
* for an enumerate op, and those ops are called in order. The properties each
* op adds to the 'properties' vector are added to the set of values the for-in
* loop will iterate over. All of this is nonstandard.
*
* An object is "enumerated" when it's the target of a for-in loop or
* JS_Enumerate(). The callback's job is to populate 'properties' with the
* object's property keys. If `enumerableOnly` is true, the callback should only
* add enumerable properties.
*/
typedef bool
(* JSNewEnumerateOp)(JSContext* cx, JS::HandleObject obj, JS::AutoIdVector& properties,
bool enumerableOnly);
/**
* The old-style JSClass.enumerate op should define all lazy properties not
* yet reflected in obj.
*/
typedef bool
(* JSEnumerateOp)(JSContext* cx, JS::HandleObject obj);
/**
* The type of ObjectOps::funToString. This callback allows an object to
* provide a custom string to use when Function.prototype.toString is invoked on
* that object. A null return value means OOM.
*/
typedef JSString*
(* JSFunToStringOp)(JSContext* cx, JS::HandleObject obj, bool isToSource);
/**
* Resolve a lazy property named by id in obj by defining it directly in obj.
* Lazy properties are those reflected from some peer native property space
* (e.g., the DOM attributes for a given node reflected as obj) on demand.
*
* JS looks for a property in an object, and if not found, tries to resolve
* the given id. *resolvedp should be set to true iff the property was defined
* on |obj|.
*/
typedef bool
(* JSResolveOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id,
bool* resolvedp);
/**
* A class with a resolve hook can optionally have a mayResolve hook. This hook
* must have no side effects and must return true for a given id if the resolve
* hook may resolve this id. This is useful when we're doing a "pure" lookup: if
* mayResolve returns false, we know we don't have to call the effectful resolve
* hook.
*
* maybeObj, if non-null, is the object on which we're doing the lookup. This
* can be nullptr: during JIT compilation we sometimes know the Class but not
* the object.
*/
typedef bool
(* JSMayResolveOp)(const JSAtomState& names, jsid id, JSObject* maybeObj);
/**
* Finalize obj, which the garbage collector has determined to be unreachable
* from other live objects or from GC roots. Obviously, finalizers must never
* store a reference to obj.
*/
typedef void
(* JSFinalizeOp)(JSFreeOp* fop, JSObject* obj);
/**
* Check whether v is an instance of obj. Return false on error or exception,
* true on success with true in *bp if v is an instance of obj, false in
* *bp otherwise.
*/
typedef bool
(* JSHasInstanceOp)(JSContext* cx, JS::HandleObject obj, JS::MutableHandleValue vp,
bool* bp);
/**
* Function type for trace operation of the class called to enumerate all
* traceable things reachable from obj's private data structure. For each such
* thing, a trace implementation must call JS::TraceEdge on the thing's
* location.
*
* JSTraceOp implementation can assume that no other threads mutates object
* state. It must not change state of the object or corresponding native
* structures. The only exception for this rule is the case when the embedding
* needs a tight integration with GC. In that case the embedding can check if
* the traversal is a part of the marking phase through calling
* JS_IsGCMarkingTracer and apply a special code like emptying caches or
* marking its native structures.
*/
typedef void
(* JSTraceOp)(JSTracer* trc, JSObject* obj);
typedef JSObject*
(* JSWeakmapKeyDelegateOp)(JSObject* obj);
typedef size_t
(* JSObjectMovedOp)(JSObject* obj, JSObject* old);
/* js::Class operation signatures. */
namespace js {
typedef bool
(* LookupPropertyOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id,
JS::MutableHandleObject objp, JS::MutableHandle<JS::PropertyResult> propp);
typedef bool
(* DefinePropertyOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id,
JS::Handle<JS::PropertyDescriptor> desc,
JS::ObjectOpResult& result);
typedef bool
(* HasPropertyOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id, bool* foundp);
typedef bool
(* GetPropertyOp)(JSContext* cx, JS::HandleObject obj, JS::HandleValue receiver, JS::HandleId id,
JS::MutableHandleValue vp);
typedef bool
(* SetPropertyOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id, JS::HandleValue v,
JS::HandleValue receiver, JS::ObjectOpResult& result);
typedef bool
(* GetOwnPropertyOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id,
JS::MutableHandle<JS::PropertyDescriptor> desc);
typedef bool
(* DeletePropertyOp)(JSContext* cx, JS::HandleObject obj, JS::HandleId id,
JS::ObjectOpResult& result);
class JS_FRIEND_API(ElementAdder)
{
public:
enum GetBehavior {
// Check if the element exists before performing the Get and preserve
// holes.
CheckHasElemPreserveHoles,
// Perform a Get operation, like obj[index] in JS.
GetElement
};
private:
// Only one of these is used.
JS::RootedObject resObj_;
JS::Value* vp_;
uint32_t index_;
#ifdef DEBUG
uint32_t length_;
#endif
GetBehavior getBehavior_;
public:
ElementAdder(JSContext* cx, JSObject* obj, uint32_t length, GetBehavior behavior)
: resObj_(cx, obj), vp_(nullptr), index_(0),
#ifdef DEBUG
length_(length),
#endif
getBehavior_(behavior)
{}
ElementAdder(JSContext* cx, JS::Value* vp, uint32_t length, GetBehavior behavior)
: resObj_(cx), vp_(vp), index_(0),
#ifdef DEBUG
length_(length),
#endif
getBehavior_(behavior)
{}
GetBehavior getBehavior() const { return getBehavior_; }
bool append(JSContext* cx, JS::HandleValue v);
void appendHole();
};
typedef bool
(* GetElementsOp)(JSContext* cx, JS::HandleObject obj, uint32_t begin, uint32_t end,
ElementAdder* adder);
typedef void
(* FinalizeOp)(FreeOp* fop, JSObject* obj);
// The special treatment of |finalize| and |trace| is necessary because if we
// assign either of those hooks to a local variable and then call it -- as is
// done with the other hooks -- the GC hazard analysis gets confused.
#define JS_CLASS_MEMBERS(ClassOpsType, FreeOpType) \
const char* name; \
uint32_t flags; \
const ClassOpsType* cOps; \
\
JSAddPropertyOp getAddProperty() const { return cOps ? cOps->addProperty : nullptr; } \
JSDeletePropertyOp getDelProperty() const { return cOps ? cOps->delProperty : nullptr; } \
JSEnumerateOp getEnumerate() const { return cOps ? cOps->enumerate : nullptr; } \
JSNewEnumerateOp getNewEnumerate()const { return cOps ? cOps->newEnumerate: nullptr; } \
JSResolveOp getResolve() const { return cOps ? cOps->resolve : nullptr; } \
JSMayResolveOp getMayResolve() const { return cOps ? cOps->mayResolve : nullptr; } \
JSNative getCall() const { return cOps ? cOps->call : nullptr; } \
JSHasInstanceOp getHasInstance() const { return cOps ? cOps->hasInstance : nullptr; } \
JSNative getConstruct() const { return cOps ? cOps->construct : nullptr; } \
\
bool hasFinalize() const { return cOps && cOps->finalize; } \
bool hasTrace() const { return cOps && cOps->trace; } \
\
bool isTrace(JSTraceOp trace) const { return cOps && cOps->trace == trace; } \
\
void doFinalize(FreeOpType* fop, JSObject* obj) const { \
MOZ_ASSERT(cOps && cOps->finalize); \
cOps->finalize(fop, obj); \
} \
void doTrace(JSTracer* trc, JSObject* obj) const { \
MOZ_ASSERT(cOps && cOps->trace); \
cOps->trace(trc, obj); \
}
// XXX: MOZ_NONHEAP_CLASS allows objects to be created statically or on the
// stack. We actually want to ban stack objects too, but that's currently not
// possible. So we define JS_STATIC_CLASS to make the intention clearer.
#define JS_STATIC_CLASS MOZ_NONHEAP_CLASS
struct JS_STATIC_CLASS ClassOps
{
/* Function pointer members (may be null). */
JSAddPropertyOp addProperty;
JSDeletePropertyOp delProperty;
JSEnumerateOp enumerate;
JSNewEnumerateOp newEnumerate;
JSResolveOp resolve;
JSMayResolveOp mayResolve;
FinalizeOp finalize;
JSNative call;
JSHasInstanceOp hasInstance;
JSNative construct;
JSTraceOp trace;
};
/** Callback for the creation of constructor and prototype objects. */
typedef JSObject* (*ClassObjectCreationOp)(JSContext* cx, JSProtoKey key);
/** Callback for custom post-processing after class initialization via ClassSpec. */
typedef bool (*FinishClassInitOp)(JSContext* cx, JS::HandleObject ctor,
JS::HandleObject proto);
const size_t JSCLASS_CACHED_PROTO_WIDTH = 6;
struct JS_STATIC_CLASS ClassSpec
{
ClassObjectCreationOp createConstructor;
ClassObjectCreationOp createPrototype;
const JSFunctionSpec* constructorFunctions;
const JSPropertySpec* constructorProperties;
const JSFunctionSpec* prototypeFunctions;
const JSPropertySpec* prototypeProperties;
FinishClassInitOp finishInit;
uintptr_t flags;
static const size_t ProtoKeyWidth = JSCLASS_CACHED_PROTO_WIDTH;
static const uintptr_t ProtoKeyMask = (1 << ProtoKeyWidth) - 1;
static const uintptr_t DontDefineConstructor = 1 << ProtoKeyWidth;
bool defined() const { return !!createConstructor; }
// The ProtoKey this class inherits from.
JSProtoKey inheritanceProtoKey() const {
MOZ_ASSERT(defined());
static_assert(JSProto_Null == 0, "zeroed key must be null");
// Default: Inherit from Object.
if (!(flags & ProtoKeyMask))
return JSProto_Object;
return JSProtoKey(flags & ProtoKeyMask);
}
bool shouldDefineConstructor() const {
MOZ_ASSERT(defined());
return !(flags & DontDefineConstructor);
}
};
struct JS_STATIC_CLASS ClassExtension
{
/**
* If an object is used as a key in a weakmap, it may be desirable for the
* garbage collector to keep that object around longer than it otherwise
* would. A common case is when the key is a wrapper around an object in
* another compartment, and we want to avoid collecting the wrapper (and
* removing the weakmap entry) as long as the wrapped object is alive. In
* that case, the wrapped object is returned by the wrapper's
* weakmapKeyDelegateOp hook. As long as the wrapper is used as a weakmap
* key, it will not be collected (and remain in the weakmap) until the
* wrapped object is collected.
*/
JSWeakmapKeyDelegateOp weakmapKeyDelegateOp;
/**
* Optional hook called when an object is moved by generational or
* compacting GC.
*
* There may exist weak pointers to an object that are not traced through
* when the normal trace APIs are used, for example objects in the wrapper
* cache. This hook allows these pointers to be updated.
*
* Note that this hook can be called before JS_NewObject() returns if a GC
* is triggered during construction of the object. This can happen for
* global objects for example.
*
* The function should return the difference between nursery bytes used and
* tenured bytes used, which may be nonzero e.g. if some nursery-allocated
* data beyond the actual GC thing is moved into malloced memory.
*
* This is used to compute the nursery promotion rate.
*/
JSObjectMovedOp objectMovedOp;
};
#define JS_NULL_CLASS_SPEC nullptr
#define JS_NULL_CLASS_EXT nullptr
struct JS_STATIC_CLASS ObjectOps
{
LookupPropertyOp lookupProperty;
DefinePropertyOp defineProperty;
HasPropertyOp hasProperty;
GetPropertyOp getProperty;
SetPropertyOp setProperty;
GetOwnPropertyOp getOwnPropertyDescriptor;
DeletePropertyOp deleteProperty;
GetElementsOp getElements;
JSFunToStringOp funToString;
};
#define JS_NULL_OBJECT_OPS nullptr
} // namespace js
// Classes, objects, and properties.
typedef void (*JSClassInternal)();
struct JS_STATIC_CLASS JSClassOps
{
/* Function pointer members (may be null). */
JSAddPropertyOp addProperty;
JSDeletePropertyOp delProperty;
JSEnumerateOp enumerate;
JSNewEnumerateOp newEnumerate;
JSResolveOp resolve;
JSMayResolveOp mayResolve;
JSFinalizeOp finalize;
JSNative call;
JSHasInstanceOp hasInstance;
JSNative construct;
JSTraceOp trace;
};
#define JS_NULL_CLASS_OPS nullptr
struct JSClass {
JS_CLASS_MEMBERS(JSClassOps, JSFreeOp);
void* reserved[3];
};
// Objects have private slot.
static const uint32_t JSCLASS_HAS_PRIVATE = 1 << 0;
// Class's initialization code will call `SetNewObjectMetadata` itself.
static const uint32_t JSCLASS_DELAY_METADATA_BUILDER = 1 << 1;
// Class is an XPCWrappedNative. WeakMaps use this to override the wrapper
// disposal mechanism.
static const uint32_t JSCLASS_IS_WRAPPED_NATIVE = 1 << 2;
// Private is `nsISupports*`.
static const uint32_t JSCLASS_PRIVATE_IS_NSISUPPORTS = 1 << 3;
// Objects are DOM.
static const uint32_t JSCLASS_IS_DOMJSCLASS = 1 << 4;
// If wrapped by an xray wrapper, the builtin class's constructor won't be
// unwrapped and invoked. Instead, the constructor is resolved in the caller's
// compartment and invoked with a wrapped newTarget. The constructor has to
// detect and handle this situation. See PromiseConstructor for details.
static const uint32_t JSCLASS_HAS_XRAYED_CONSTRUCTOR = 1 << 5;
// Objects of this class act like the value undefined, in some contexts.
static const uint32_t JSCLASS_EMULATES_UNDEFINED = 1 << 6;
// Reserved for embeddings.
static const uint32_t JSCLASS_USERBIT1 = 1 << 7;
// To reserve slots fetched and stored via JS_Get/SetReservedSlot, bitwise-or
// JSCLASS_HAS_RESERVED_SLOTS(n) into the initializer for JSClass.flags, where n
// is a constant in [1, 255]. Reserved slots are indexed from 0 to n-1.
// Room for 8 flags below ...
static const uintptr_t JSCLASS_RESERVED_SLOTS_SHIFT = 8;
// ... and 16 above this field.
static const uint32_t JSCLASS_RESERVED_SLOTS_WIDTH = 8;
static const uint32_t JSCLASS_RESERVED_SLOTS_MASK = JS_BITMASK(JSCLASS_RESERVED_SLOTS_WIDTH);
#define JSCLASS_HAS_RESERVED_SLOTS(n) (((n) & JSCLASS_RESERVED_SLOTS_MASK) \
<< JSCLASS_RESERVED_SLOTS_SHIFT)
#define JSCLASS_RESERVED_SLOTS(clasp) (((clasp)->flags \
>> JSCLASS_RESERVED_SLOTS_SHIFT) \
& JSCLASS_RESERVED_SLOTS_MASK)
#define JSCLASS_HIGH_FLAGS_SHIFT (JSCLASS_RESERVED_SLOTS_SHIFT + \
JSCLASS_RESERVED_SLOTS_WIDTH)
static const uint32_t JSCLASS_IS_ANONYMOUS = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 0);
static const uint32_t JSCLASS_IS_GLOBAL = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 1);
static const uint32_t JSCLASS_INTERNAL_FLAG2 = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 2);
static const uint32_t JSCLASS_INTERNAL_FLAG3 = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 3);
static const uint32_t JSCLASS_IS_PROXY = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 4);
static const uint32_t JSCLASS_SKIP_NURSERY_FINALIZE = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 5);
// Reserved for embeddings.
static const uint32_t JSCLASS_USERBIT2 = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 6);
static const uint32_t JSCLASS_USERBIT3 = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 7);
static const uint32_t JSCLASS_BACKGROUND_FINALIZE = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 8);
static const uint32_t JSCLASS_FOREGROUND_FINALIZE = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 9);
// Bits 26 through 31 are reserved for the CACHED_PROTO_KEY mechanism, see
// below.
// ECMA-262 requires that most constructors used internally create objects
// with "the original Foo.prototype value" as their [[Prototype]] (__proto__)
// member initial value. The "original ... value" verbiage is there because
// in ECMA-262, global properties naming class objects are read/write and
// deleteable, for the most part.
//
// Implementing this efficiently requires that global objects have classes
// with the following flags. Failure to use JSCLASS_GLOBAL_FLAGS was
// previously allowed, but is now an ES5 violation and thus unsupported.
//
// JSCLASS_GLOBAL_APPLICATION_SLOTS is the number of slots reserved at
// the beginning of every global object's slots for use by the
// application.
static const uint32_t JSCLASS_GLOBAL_APPLICATION_SLOTS = 5;
static const uint32_t JSCLASS_GLOBAL_SLOT_COUNT =
JSCLASS_GLOBAL_APPLICATION_SLOTS + JSProto_LIMIT * 2 + 37;
#define JSCLASS_GLOBAL_FLAGS_WITH_SLOTS(n) \
(JSCLASS_IS_GLOBAL | JSCLASS_HAS_RESERVED_SLOTS(JSCLASS_GLOBAL_SLOT_COUNT + (n)))
#define JSCLASS_GLOBAL_FLAGS \
JSCLASS_GLOBAL_FLAGS_WITH_SLOTS(0)
#define JSCLASS_HAS_GLOBAL_FLAG_AND_SLOTS(clasp) \
(((clasp)->flags & JSCLASS_IS_GLOBAL) \
&& JSCLASS_RESERVED_SLOTS(clasp) >= JSCLASS_GLOBAL_SLOT_COUNT)
// Fast access to the original value of each standard class's prototype.
static const uint32_t JSCLASS_CACHED_PROTO_SHIFT = JSCLASS_HIGH_FLAGS_SHIFT + 10;
static const uint32_t JSCLASS_CACHED_PROTO_MASK = JS_BITMASK(js::JSCLASS_CACHED_PROTO_WIDTH);
#define JSCLASS_HAS_CACHED_PROTO(key) (uint32_t(key) << JSCLASS_CACHED_PROTO_SHIFT)
#define JSCLASS_CACHED_PROTO_KEY(clasp) ((JSProtoKey) \
(((clasp)->flags \
>> JSCLASS_CACHED_PROTO_SHIFT) \
& JSCLASS_CACHED_PROTO_MASK))
// Initializer for unused members of statically initialized JSClass structs.
#define JSCLASS_NO_INTERNAL_MEMBERS {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}
#define JSCLASS_NO_OPTIONAL_MEMBERS 0,0,0,0,0,JSCLASS_NO_INTERNAL_MEMBERS
namespace js {
struct JS_STATIC_CLASS Class
{
JS_CLASS_MEMBERS(js::ClassOps, FreeOp);
const ClassSpec* spec;
const ClassExtension* ext;
const ObjectOps* oOps;
/*
* Objects of this class aren't native objects. They don't have Shapes that
* describe their properties and layout. Classes using this flag must
* provide their own property behavior, either by being proxy classes (do
* this) or by overriding all the ObjectOps except getElements
* (don't do this).
*/
static const uint32_t NON_NATIVE = JSCLASS_INTERNAL_FLAG2;
bool isNative() const {
return !(flags & NON_NATIVE);
}
bool hasPrivate() const {
return !!(flags & JSCLASS_HAS_PRIVATE);
}
bool emulatesUndefined() const {
return flags & JSCLASS_EMULATES_UNDEFINED;
}
bool isJSFunction() const {
return this == js::FunctionClassPtr;
}
bool nonProxyCallable() const {
MOZ_ASSERT(!isProxy());
return isJSFunction() || getCall();
}
bool isProxy() const {
return flags & JSCLASS_IS_PROXY;
}
bool isDOMClass() const {
return flags & JSCLASS_IS_DOMJSCLASS;
}
bool shouldDelayMetadataBuilder() const {
return flags & JSCLASS_DELAY_METADATA_BUILDER;
}
bool isWrappedNative() const {
return flags & JSCLASS_IS_WRAPPED_NATIVE;
}
static size_t offsetOfFlags() { return offsetof(Class, flags); }
bool specDefined() const { return spec ? spec->defined() : false; }
JSProtoKey specInheritanceProtoKey()
const { return spec ? spec->inheritanceProtoKey() : JSProto_Null; }
bool specShouldDefineConstructor()
const { return spec ? spec->shouldDefineConstructor() : true; }
ClassObjectCreationOp specCreateConstructorHook()
const { return spec ? spec->createConstructor : nullptr; }
ClassObjectCreationOp specCreatePrototypeHook()
const { return spec ? spec->createPrototype : nullptr; }
const JSFunctionSpec* specConstructorFunctions()
const { return spec ? spec->constructorFunctions : nullptr; }
const JSPropertySpec* specConstructorProperties()
const { return spec ? spec->constructorProperties : nullptr; }
const JSFunctionSpec* specPrototypeFunctions()
const { return spec ? spec->prototypeFunctions : nullptr; }
const JSPropertySpec* specPrototypeProperties()
const { return spec ? spec->prototypeProperties : nullptr; }
FinishClassInitOp specFinishInitHook()
const { return spec ? spec->finishInit : nullptr; }
JSWeakmapKeyDelegateOp extWeakmapKeyDelegateOp()
const { return ext ? ext->weakmapKeyDelegateOp : nullptr; }
JSObjectMovedOp extObjectMovedOp()
const { return ext ? ext->objectMovedOp : nullptr; }
LookupPropertyOp getOpsLookupProperty() const { return oOps ? oOps->lookupProperty : nullptr; }
DefinePropertyOp getOpsDefineProperty() const { return oOps ? oOps->defineProperty : nullptr; }
HasPropertyOp getOpsHasProperty() const { return oOps ? oOps->hasProperty : nullptr; }
GetPropertyOp getOpsGetProperty() const { return oOps ? oOps->getProperty : nullptr; }
SetPropertyOp getOpsSetProperty() const { return oOps ? oOps->setProperty : nullptr; }
GetOwnPropertyOp getOpsGetOwnPropertyDescriptor()
const { return oOps ? oOps->getOwnPropertyDescriptor
: nullptr; }
DeletePropertyOp getOpsDeleteProperty() const { return oOps ? oOps->deleteProperty : nullptr; }
GetElementsOp getOpsGetElements() const { return oOps ? oOps->getElements : nullptr; }
JSFunToStringOp getOpsFunToString() const { return oOps ? oOps->funToString : nullptr; }
};
static_assert(offsetof(JSClassOps, addProperty) == offsetof(ClassOps, addProperty),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClassOps, delProperty) == offsetof(ClassOps, delProperty),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClassOps, enumerate) == offsetof(ClassOps, enumerate),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClassOps, newEnumerate) == offsetof(ClassOps, newEnumerate),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClassOps, resolve) == offsetof(ClassOps, resolve),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClassOps, mayResolve) == offsetof(ClassOps, mayResolve),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClassOps, finalize) == offsetof(ClassOps, finalize),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClassOps, call) == offsetof(ClassOps, call),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClassOps, construct) == offsetof(ClassOps, construct),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClassOps, hasInstance) == offsetof(ClassOps, hasInstance),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClassOps, trace) == offsetof(ClassOps, trace),
"ClassOps and JSClassOps must be consistent");
static_assert(sizeof(JSClassOps) == sizeof(ClassOps),
"ClassOps and JSClassOps must be consistent");
static_assert(offsetof(JSClass, name) == offsetof(Class, name),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, flags) == offsetof(Class, flags),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, cOps) == offsetof(Class, cOps),
"Class and JSClass must be consistent");
static_assert(sizeof(JSClass) == sizeof(Class),
"Class and JSClass must be consistent");
static MOZ_ALWAYS_INLINE const JSClass*
Jsvalify(const Class* c)
{
return (const JSClass*)c;
}
static MOZ_ALWAYS_INLINE const Class*
Valueify(const JSClass* c)
{
return (const Class*)c;
}
/**
* Enumeration describing possible values of the [[Class]] internal property
* value of objects.
*/
enum class ESClass {
Object,
Array,
Number,
String,
Boolean,
RegExp,
ArrayBuffer,
SharedArrayBuffer,
Date,
Set,
Map,
Promise,
MapIterator,
SetIterator,
Arguments,
Error,
/** None of the above. */
Other
};
/* Fills |vp| with the unboxed value for boxed types, or undefined otherwise. */
bool
Unbox(JSContext* cx, JS::HandleObject obj, JS::MutableHandleValue vp);
#ifdef DEBUG
JS_FRIEND_API(bool)
HasObjectMovedOp(JSObject* obj);
#endif
} /* namespace js */
#endif /* js_Class_h */
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