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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 "mozilla/DebugOnly.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 JSFreeOp;
struct JSFunctionSpec;
namespace js {
struct Class;
class FreeOp;
class PropertyName;
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 {
class AutoIdVector;
}
// JSClass operation signatures.
// Add or 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
(* JSPropertyOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
JS::MutableHandleValue vp);
// 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). The *vp out
// parameter, on success, is the new property value after the
// set.
typedef bool
(* JSStrictPropertyOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
bool strict, JS::MutableHandleValue vp);
// 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), set *succeeded to false 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),
// set *succeeded to true and return true.
typedef bool
(* JSDeletePropertyOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
bool *succeeded);
// 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().
// All other property inspection, including Object.keys(obj), goes through [[OwnKeys]].
//
// The callback's job is to populate 'properties' with all property keys that the for-in loop
// should visit.
typedef bool
(* JSNewEnumerateOp)(JSContext *cx, JS::HandleObject obj, JS::AutoIdVector &properties);
// The old-style JSClass.enumerate op should define all lazy properties not
// yet reflected in obj.
typedef bool
(* JSEnumerateOp)(JSContext *cx, JS::HandleObject obj);
// 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
// was defined on |obj|.
//
typedef bool
(* JSResolveOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
bool *resolvedp);
// Convert obj to the given type, returning true with the resulting value in
// *vp on success, and returning false on error or exception.
typedef bool
(* JSConvertOp)(JSContext *cx, JS::HandleObject obj, JSType type,
JS::MutableHandleValue vp);
// 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);
// Finalizes external strings created by JS_NewExternalString.
struct JSStringFinalizer {
void (*finalize)(const JSStringFinalizer *fin, char16_t *chars);
};
// 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 one of the JS_Call*Tracer variants
// on the thing.
//
// 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 void
(* JSObjectMovedOp)(JSObject *obj, const JSObject *old);
/* js::Class operation signatures. */
namespace js {
typedef bool
(* LookupPropertyOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
JS::MutableHandleObject objp, JS::MutableHandle<Shape*> propp);
typedef bool
(* DefinePropertyOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id, JS::HandleValue value,
JSPropertyOp getter, JSStrictPropertyOp setter, unsigned attrs);
typedef bool
(* GetPropertyOp)(JSContext *cx, JS::HandleObject obj, JS::HandleObject receiver, JS::HandleId id,
JS::MutableHandleValue vp);
typedef bool
(* SetPropertyOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
JS::MutableHandleValue vp, bool strict);
typedef bool
(* GetOwnPropertyOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
JS::MutableHandle<JSPropertyDescriptor> desc);
typedef bool
(* DeletePropertyOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id, bool *succeeded);
typedef bool
(* WatchOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id, JS::HandleObject callable);
typedef bool
(* UnwatchOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id);
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_;
mozilla::DebugOnly<uint32_t> length_;
GetBehavior getBehavior_;
public:
ElementAdder(JSContext *cx, JSObject *obj, uint32_t length, GetBehavior behavior)
: resObj_(cx, obj), vp_(nullptr), index_(0), length_(length), getBehavior_(behavior)
{}
ElementAdder(JSContext *cx, JS::Value *vp, uint32_t length, GetBehavior behavior)
: resObj_(cx), vp_(vp), index_(0), length_(length), getBehavior_(behavior)
{}
GetBehavior getBehavior() const { return getBehavior_; }
void append(JSContext *cx, JS::HandleValue v);
void appendHole();
};
typedef bool
(* GetElementsOp)(JSContext *cx, JS::HandleObject obj, uint32_t begin, uint32_t end,
ElementAdder *adder);
// A generic type for functions mapping an object to another object, or null
// if an error or exception was thrown on cx.
typedef JSObject *
(* ObjectOp)(JSContext *cx, JS::HandleObject obj);
// Hook to map an object to its inner object. Infallible.
typedef JSObject *
(* InnerObjectOp)(JSObject *obj);
typedef void
(* FinalizeOp)(FreeOp *fop, JSObject *obj);
#define JS_CLASS_MEMBERS(FinalizeOpType) \
const char *name; \
uint32_t flags; \
\
/* Function pointer members (may be null). */ \
JSPropertyOp addProperty; \
JSDeletePropertyOp delProperty; \
JSPropertyOp getProperty; \
JSStrictPropertyOp setProperty; \
JSEnumerateOp enumerate; \
JSResolveOp resolve; \
JSConvertOp convert; \
FinalizeOpType 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 ClassSpec
{
ClassObjectCreationOp createConstructor;
ClassObjectCreationOp createPrototype;
const JSFunctionSpec *constructorFunctions;
const JSFunctionSpec *prototypeFunctions;
const JSPropertySpec *prototypeProperties;
FinishClassInitOp finishInit;
uintptr_t flags;
static const size_t ParentKeyWidth = JSCLASS_CACHED_PROTO_WIDTH;
static const uintptr_t ParentKeyMask = (1 << ParentKeyWidth) - 1;
static const uintptr_t DontDefineConstructor = 1 << ParentKeyWidth;
bool defined() const { return !!createConstructor; }
bool dependent() const {
MOZ_ASSERT(defined());
return (flags & ParentKeyMask);
}
JSProtoKey parentKey() const {
static_assert(JSProto_Null == 0, "zeroed key must be null");
return JSProtoKey(flags & ParentKeyMask);
}
bool shouldDefineConstructor() const {
MOZ_ASSERT(defined());
return !(flags & DontDefineConstructor);
}
};
struct ClassExtension
{
ObjectOp outerObject;
InnerObjectOp innerObject;
/*
* isWrappedNative is true only if the class is an XPCWrappedNative.
* WeakMaps use this to override the wrapper disposal optimization.
*/
bool isWrappedNative;
/*
* 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 a 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.
*/
JSObjectMovedOp objectMovedOp;
};
#define JS_NULL_CLASS_SPEC {nullptr,nullptr,nullptr,nullptr,nullptr,nullptr}
#define JS_NULL_CLASS_EXT {nullptr,nullptr,false,nullptr,nullptr}
struct ObjectOps
{
LookupPropertyOp lookupProperty;
DefinePropertyOp defineProperty;
GetPropertyOp getProperty;
SetPropertyOp setProperty;
GetOwnPropertyOp getOwnPropertyDescriptor;
DeletePropertyOp deleteProperty;
WatchOp watch;
UnwatchOp unwatch;
GetElementsOp getElements;
JSNewEnumerateOp enumerate;
ObjectOp thisObject;
};
#define JS_NULL_OBJECT_OPS \
{nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr, \
nullptr, nullptr, nullptr}
} // namespace js
// Classes, objects, and properties.
typedef void (*JSClassInternal)();
struct JSClass {
JS_CLASS_MEMBERS(JSFinalizeOp);
void *reserved[23];
};
#define JSCLASS_HAS_PRIVATE (1<<0) // objects have private slot
#define JSCLASS_PRIVATE_IS_NSISUPPORTS (1<<3) // private is (nsISupports *)
#define JSCLASS_IS_DOMJSCLASS (1<<4) // objects are DOM
#define JSCLASS_IMPLEMENTS_BARRIERS (1<<5) // Correctly implements GC read
// and write barriers
#define JSCLASS_EMULATES_UNDEFINED (1<<6) // objects of this class act
// like the value undefined,
// in some contexts
#define JSCLASS_USERBIT1 (1<<7) // Reserved for embeddings.
// 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.
#define JSCLASS_RESERVED_SLOTS_SHIFT 8 // room for 8 flags below */
#define JSCLASS_RESERVED_SLOTS_WIDTH 8 // and 16 above this field */
#define 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)
#define JSCLASS_IS_ANONYMOUS (1<<(JSCLASS_HIGH_FLAGS_SHIFT+0))
#define JSCLASS_IS_GLOBAL (1<<(JSCLASS_HIGH_FLAGS_SHIFT+1))
#define JSCLASS_INTERNAL_FLAG2 (1<<(JSCLASS_HIGH_FLAGS_SHIFT+2))
#define JSCLASS_INTERNAL_FLAG3 (1<<(JSCLASS_HIGH_FLAGS_SHIFT+3))
#define JSCLASS_IS_PROXY (1<<(JSCLASS_HIGH_FLAGS_SHIFT+4))
#define JSCLASS_FINALIZE_FROM_NURSERY (1<<(JSCLASS_HIGH_FLAGS_SHIFT+5))
// Reserved for embeddings.
#define JSCLASS_USERBIT2 (1<<(JSCLASS_HIGH_FLAGS_SHIFT+6))
#define JSCLASS_USERBIT3 (1<<(JSCLASS_HIGH_FLAGS_SHIFT+7))
#define JSCLASS_BACKGROUND_FINALIZE (1<<(JSCLASS_HIGH_FLAGS_SHIFT+8))
// 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.
#define JSCLASS_GLOBAL_APPLICATION_SLOTS 4
#define JSCLASS_GLOBAL_SLOT_COUNT (JSCLASS_GLOBAL_APPLICATION_SLOTS + JSProto_LIMIT * 3 + 31)
#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.
#define JSCLASS_CACHED_PROTO_SHIFT (JSCLASS_HIGH_FLAGS_SHIFT + 10)
#define JSCLASS_CACHED_PROTO_MASK JS_BITMASK(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 Class
{
JS_CLASS_MEMBERS(FinalizeOp);
ClassSpec spec;
ClassExtension ext;
ObjectOps ops;
/*
* 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, watch,
* unwatch, and thisObject (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() || call;
}
bool isProxy() const {
return flags & JSCLASS_IS_PROXY;
}
bool isDOMClass() const {
return flags & JSCLASS_IS_DOMJSCLASS;
}
static size_t offsetOfFlags() { return offsetof(Class, flags); }
};
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, addProperty) == offsetof(Class, addProperty),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, delProperty) == offsetof(Class, delProperty),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, getProperty) == offsetof(Class, getProperty),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, setProperty) == offsetof(Class, setProperty),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, enumerate) == offsetof(Class, enumerate),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, resolve) == offsetof(Class, resolve),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, convert) == offsetof(Class, convert),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, finalize) == offsetof(Class, finalize),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, call) == offsetof(Class, call),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, construct) == offsetof(Class, construct),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, hasInstance) == offsetof(Class, hasInstance),
"Class and JSClass must be consistent");
static_assert(offsetof(JSClass, trace) == offsetof(Class, trace),
"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 ESClassValue {
ESClass_Object, ESClass_Array, ESClass_Number, ESClass_String,
ESClass_Boolean, ESClass_RegExp, ESClass_ArrayBuffer, ESClass_SharedArrayBuffer,
ESClass_Date, ESClass_Set, ESClass_Map,
// Special snowflake for the ES6 IsArray method.
// Please don't use it without calling that function.
ESClass_IsArray
};
/*
* Return whether the given object has the given [[Class]] internal property
* value. Beware, this query says nothing about the js::Class of the JSObject
* so the caller must not assume anything about obj's representation (e.g., obj
* may be a proxy).
*/
inline bool
ObjectClassIs(JSObject &obj, ESClassValue classValue, JSContext *cx);
/* Just a helper that checks v.isObject before calling ObjectClassIs. */
inline bool
IsObjectWithClass(const JS::Value &v, ESClassValue classValue, JSContext *cx);
/* Fills |vp| with the unboxed value for boxed types, or undefined otherwise. */
inline 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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