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Diffstat (limited to 'js/public/Class.h')
| -rw-r--r-- | js/public/Class.h | 938 |
1 files changed, 938 insertions, 0 deletions
diff --git a/js/public/Class.h b/js/public/Class.h new file mode 100644 index 0000000000..e0a9f60eec --- /dev/null +++ b/js/public/Class.h @@ -0,0 +1,938 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- + * vim: set ts=8 sts=2 et sw=2 tw=80: + * 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 "mozilla/Attributes.h" + +#include "jstypes.h" + +#include "js/CallArgs.h" +#include "js/HeapAPI.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. + * It contains some engine-private extensions that allows more control over + * object behavior and, e.g., allows custom slow layout. + */ + +struct JSAtomState; +struct JSFunctionSpec; + +namespace js { + +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 JSClass* const FunctionClassPtr; + +} // namespace js + +namespace JS { + +/** + * 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(result.ok()); + * 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 JS friend API and are defined in + * js/public/friend/ErrorNumbers.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(); + JS_PUBLIC_API bool failNotDataDescriptor(); + + // Careful: This case has special handling in Object.defineProperty. + JS_PUBLIC_API bool failCantDefineWindowNonConfigurable(); + + uint32_t failureCode() const { + MOZ_ASSERT(!ok()); + return uint32_t(code_); + } + + /* + * Report an error if necessary; return true to proceed and + * false if an error was reported. + * + * The precise rules are like this: + * + * - If ok(), then we succeeded. Do nothing and return true. + * - Otherwise, if |strict| is true, throw a TypeError and return false. + * - Otherwise, do nothing and return true. + */ + bool checkStrictModeError(JSContext* cx, HandleObject obj, HandleId id, + bool strict) { + if (ok() || !strict) { + return true; + } + return reportError(cx, obj, id); + } + + /* + * The same as checkStrictModeError(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 checkStrictModeError(JSContext* cx, HandleObject obj, bool strict) { + if (ok() || !strict) { + return true; + } + return reportError(cx, obj); + } + + /* Throw a TypeError. Call this only if !ok(). */ + bool reportError(JSContext* cx, HandleObject obj, HandleId id); + + /* + * The same as reportError(cx, obj, id), except the operation is not + * associated with a particular property id. + */ + bool reportError(JSContext* cx, HandleObject obj); + + // Convenience method. Return true if ok(); otherwise throw a TypeError + // and return false. + bool checkStrict(JSContext* cx, HandleObject obj, HandleId id) { + return checkStrictModeError(cx, obj, id, true); + } + + // Convenience method. The same as checkStrict(cx, obj, id), except the + // operation is not associated with a particular property id. + bool checkStrict(JSContext* cx, HandleObject obj) { + return checkStrictModeError(cx, obj, true); + } +}; + +class PropertyResult { + enum class Kind : uint8_t { + NotFound, + NativeProperty, + NonNativeProperty, + DenseElement, + TypedArrayElement, + }; + union { + // Set if kind is NativeProperty. + js::Shape* shape_; + // Set if kind is DenseElement. + uint32_t denseIndex_; + // Set if kind is TypedArrayElement. + size_t typedArrayIndex_; + }; + Kind kind_ = Kind::NotFound; + + public: + PropertyResult() = default; + + explicit operator bool() const { return isFound(); } + + bool isFound() const { return kind_ != Kind::NotFound; } + bool isNonNativeProperty() const { return kind_ == Kind::NonNativeProperty; } + bool isDenseElement() const { return kind_ == Kind::DenseElement; } + bool isTypedArrayElement() const { return kind_ == Kind::TypedArrayElement; } + bool isNativeProperty() const { return kind_ == Kind::NativeProperty; } + + js::Shape* shape() const { + MOZ_ASSERT(isNativeProperty()); + return shape_; + } + + uint32_t denseElementIndex() const { + MOZ_ASSERT(isDenseElement()); + return denseIndex_; + } + + size_t typedArrayElementIndex() const { + MOZ_ASSERT(isTypedArrayElement()); + return typedArrayIndex_; + } + + void setNotFound() { kind_ = Kind::NotFound; } + + void setNativeProperty(js::Shape* propertyShape) { + kind_ = Kind::NativeProperty; + shape_ = propertyShape; + } + + void setNonNativeProperty() { kind_ = Kind::NonNativeProperty; } + + void setDenseElement(uint32_t index) { + kind_ = Kind::DenseElement; + denseIndex_ = index; + } + + void setTypedArrayElement(size_t index) { + kind_ = Kind::TypedArrayElement; + typedArrayIndex_ = index; + } + + 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* shape() const { return value().shape(); } + uint32_t denseElementIndex() const { return value().denseElementIndex(); } + size_t typedArrayElementIndex() const { + return value().typedArrayElementIndex(); + } + bool isNativeProperty() const { return value().isNativeProperty(); } + bool isNonNativeProperty() const { return value().isNonNativeProperty(); } + bool isDenseElement() const { return value().isDenseElement(); } + bool isTypedArrayElement() const { return value().isTypedArrayElement(); } +}; + +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 setDenseElement(uint32_t index) { value().setDenseElement(index); } + void setTypedArrayElement(size_t index) { + value().setTypedArrayElement(index); + } +}; + +} // 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::MutableHandleIdVector 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 size_t (*JSObjectMovedOp)(JSObject* obj, JSObject* old); + +namespace js { + +/* Internal / friend API operation signatures. */ + +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); + +/** 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 = 7; + +struct MOZ_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 MOZ_STATIC_CLASS ClassExtension { + /** + * 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; +}; + +struct MOZ_STATIC_CLASS ObjectOps { + LookupPropertyOp lookupProperty; + DefinePropertyOp defineProperty; + HasPropertyOp hasProperty; + GetPropertyOp getProperty; + SetPropertyOp setProperty; + GetOwnPropertyOp getOwnPropertyDescriptor; + DeletePropertyOp deleteProperty; + GetElementsOp getElements; + JSFunToStringOp funToString; +}; + +} // namespace js + +static constexpr const js::ClassSpec* JS_NULL_CLASS_SPEC = nullptr; +static constexpr const js::ClassExtension* JS_NULL_CLASS_EXT = nullptr; + +static constexpr const js::ObjectOps* JS_NULL_OBJECT_OPS = nullptr; + +// Classes, objects, and properties. + +// 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); + +static constexpr uint32_t JSCLASS_HAS_RESERVED_SLOTS(uint32_t n) { + return (n & JSCLASS_RESERVED_SLOTS_MASK) << JSCLASS_RESERVED_SLOTS_SHIFT; +} + +static constexpr uint32_t JSCLASS_HIGH_FLAGS_SHIFT = + JSCLASS_RESERVED_SLOTS_SHIFT + JSCLASS_RESERVED_SLOTS_WIDTH; + +static const uint32_t JSCLASS_INTERNAL_FLAG1 = + 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_IS_PROXY = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 3); +static const uint32_t JSCLASS_SKIP_NURSERY_FINALIZE = + 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 4); + +// Reserved for embeddings. +static const uint32_t JSCLASS_USERBIT2 = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 5); +static const uint32_t JSCLASS_USERBIT3 = 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 6); + +static const uint32_t JSCLASS_BACKGROUND_FINALIZE = + 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 7); +static const uint32_t JSCLASS_FOREGROUND_FINALIZE = + 1 << (JSCLASS_HIGH_FLAGS_SHIFT + 8); + +// Bits 25 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 + 28; + +static constexpr uint32_t JSCLASS_GLOBAL_FLAGS_WITH_SLOTS(uint32_t n) { + return JSCLASS_IS_GLOBAL | + JSCLASS_HAS_RESERVED_SLOTS(JSCLASS_GLOBAL_SLOT_COUNT + n); +} + +static constexpr uint32_t JSCLASS_GLOBAL_FLAGS = + JSCLASS_GLOBAL_FLAGS_WITH_SLOTS(0); + +// Fast access to the original value of each standard class's prototype. +static const uint32_t JSCLASS_CACHED_PROTO_SHIFT = JSCLASS_HIGH_FLAGS_SHIFT + 9; +static const uint32_t JSCLASS_CACHED_PROTO_MASK = + js::BitMask(js::JSCLASS_CACHED_PROTO_WIDTH); + +static_assert(JSProto_LIMIT <= (JSCLASS_CACHED_PROTO_MASK + 1), + "JSProtoKey must not exceed the maximum cacheable proto-mask"); + +static constexpr uint32_t JSCLASS_HAS_CACHED_PROTO(JSProtoKey key) { + return uint32_t(key) << JSCLASS_CACHED_PROTO_SHIFT; +} + +struct MOZ_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; +}; + +static constexpr const JSClassOps* JS_NULL_CLASS_OPS = nullptr; + +struct alignas(js::gc::JSClassAlignBytes) JSClass { + const char* name; + uint32_t flags; + const JSClassOps* cOps; + + const js::ClassSpec* spec; + const js::ClassExtension* ext; + const js::ObjectOps* oOps; + + // Public accessors: + + 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; } + + // 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. + void doFinalize(JSFreeOp* 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); + } + + /* + * 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 isGlobal() const { return flags & JSCLASS_IS_GLOBAL; } + + 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(JSClass, flags); } + + // Internal / friend API accessors: + + 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; + } + js::ClassObjectCreationOp specCreateConstructorHook() const { + return spec ? spec->createConstructor : nullptr; + } + js::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; + } + js::FinishClassInitOp specFinishInitHook() const { + return spec ? spec->finishInit : nullptr; + } + + JSObjectMovedOp extObjectMovedOp() const { + return ext ? ext->objectMovedOp : nullptr; + } + + js::LookupPropertyOp getOpsLookupProperty() const { + return oOps ? oOps->lookupProperty : nullptr; + } + js::DefinePropertyOp getOpsDefineProperty() const { + return oOps ? oOps->defineProperty : nullptr; + } + js::HasPropertyOp getOpsHasProperty() const { + return oOps ? oOps->hasProperty : nullptr; + } + js::GetPropertyOp getOpsGetProperty() const { + return oOps ? oOps->getProperty : nullptr; + } + js::SetPropertyOp getOpsSetProperty() const { + return oOps ? oOps->setProperty : nullptr; + } + js::GetOwnPropertyOp getOpsGetOwnPropertyDescriptor() const { + return oOps ? oOps->getOwnPropertyDescriptor : nullptr; + } + js::DeletePropertyOp getOpsDeleteProperty() const { + return oOps ? oOps->deleteProperty : nullptr; + } + js::GetElementsOp getOpsGetElements() const { + return oOps ? oOps->getElements : nullptr; + } + JSFunToStringOp getOpsFunToString() const { + return oOps ? oOps->funToString : nullptr; + } +}; + +static constexpr uint32_t JSCLASS_RESERVED_SLOTS(const JSClass* clasp) { + return (clasp->flags >> JSCLASS_RESERVED_SLOTS_SHIFT) & + JSCLASS_RESERVED_SLOTS_MASK; +} + +static constexpr bool JSCLASS_HAS_GLOBAL_FLAG_AND_SLOTS(const JSClass* clasp) { + return (clasp->flags & JSCLASS_IS_GLOBAL) && + JSCLASS_RESERVED_SLOTS(clasp) >= JSCLASS_GLOBAL_SLOT_COUNT; +} + +static constexpr JSProtoKey JSCLASS_CACHED_PROTO_KEY(const JSClass* clasp) { + return JSProtoKey((clasp->flags >> JSCLASS_CACHED_PROTO_SHIFT) & + JSCLASS_CACHED_PROTO_MASK); +} + +namespace js { + +/** + * 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, + BigInt, + Function, // Note: Only JSFunction objects. + + /** 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 */ |