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gecko/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/NullPtr.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.
*/
class JSFreeOp;
struct JSFunctionSpec;
namespace js {
class 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
// 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);
// This function type is used for callbacks that enumerate the properties of
// a JSObject. The behavior depends on the value of enum_op:
//
// JSENUMERATE_INIT
// A new, opaque iterator state should be allocated and stored in *statep.
// (You can use PRIVATE_TO_JSVAL() to tag the pointer to be stored).
//
// The number of properties that will be enumerated should be returned as
// an integer jsval in *idp, if idp is non-null, and provided the number of
// enumerable properties is known. If idp is non-null and the number of
// enumerable properties can't be computed in advance, *idp should be set
// to JSVAL_ZERO.
//
// JSENUMERATE_INIT_ALL
// Used identically to JSENUMERATE_INIT, but exposes all properties of the
// object regardless of enumerability.
//
// JSENUMERATE_NEXT
// A previously allocated opaque iterator state is passed in via statep.
// Return the next jsid in the iteration using *idp. The opaque iterator
// state pointed at by statep is destroyed and *statep is set to JSVAL_NULL
// if there are no properties left to enumerate.
//
// JSENUMERATE_DESTROY
// Destroy the opaque iterator state previously allocated in *statep by a
// call to this function when enum_op was JSENUMERATE_INIT or
// JSENUMERATE_INIT_ALL.
//
// The return value is used to indicate success, with a value of false
// indicating failure.
typedef bool
(* JSNewEnumerateOp)(JSContext *cx, JS::HandleObject obj, JSIterateOp enum_op,
JS::MutableHandleValue statep, JS::MutableHandleId idp);
// 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. If resolve succeeds, the engine looks again in case resolve
// defined obj[id]. If no such property exists directly in obj, the process
// is repeated with obj's prototype, etc.
//
// NB: JSNewResolveOp provides a cheaper way to resolve lazy properties.
typedef bool
(* JSResolveOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id);
// Like JSResolveOp, except the *objp out parameter, on success, should be null
// to indicate that id was not resolved; and non-null, referring to obj or one
// of its prototypes, if id was resolved. The hook may assume *objp is null on
// entry.
//
// This hook instead of JSResolveOp is called via the JSClass.resolve member
// if JSCLASS_NEW_RESOLVE is set in JSClass.flags.
typedef bool
(* JSNewResolveOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
JS::MutableHandleObject objp);
// 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, jschar *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);
// A generic type for functions mapping an object to another object, or null
// if an error or exception was thrown on cx.
typedef JSObject *
(* JSObjectOp)(JSContext *cx, JS::HandleObject obj);
// Hook that creates an iterator object for a given object. Returns the
// iterator object or null if an error or exception was thrown on cx.
typedef JSObject *
(* JSIteratorOp)(JSContext *cx, JS::HandleObject obj, bool keysonly);
typedef JSObject *
(* JSWeakmapKeyDelegateOp)(JSObject *obj);
/* js::Class operation signatures. */
namespace js {
typedef bool
(* LookupGenericOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
JS::MutableHandleObject objp, JS::MutableHandle<Shape*> propp);
typedef bool
(* LookupPropOp)(JSContext *cx, JS::HandleObject obj, JS::Handle<PropertyName*> name,
JS::MutableHandleObject objp, JS::MutableHandle<Shape*> propp);
typedef bool
(* LookupElementOp)(JSContext *cx, JS::HandleObject obj, uint32_t index,
JS::MutableHandleObject objp, JS::MutableHandle<Shape*> propp);
typedef bool
(* DefineGenericOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id, JS::HandleValue value,
JSPropertyOp getter, JSStrictPropertyOp setter, unsigned attrs);
typedef bool
(* DefinePropOp)(JSContext *cx, JS::HandleObject obj, JS::Handle<PropertyName*> name,
JS::HandleValue value, JSPropertyOp getter, JSStrictPropertyOp setter,
unsigned attrs);
typedef bool
(* DefineElementOp)(JSContext *cx, JS::HandleObject obj, uint32_t index, JS::HandleValue value,
JSPropertyOp getter, JSStrictPropertyOp setter, unsigned attrs);
typedef bool
(* GenericIdOp)(JSContext *cx, JS::HandleObject obj, JS::HandleObject receiver, JS::HandleId id,
JS::MutableHandleValue vp);
typedef bool
(* PropertyIdOp)(JSContext *cx, JS::HandleObject obj, JS::HandleObject receiver,
JS::Handle<PropertyName*> name, JS::MutableHandleValue vp);
typedef bool
(* ElementIdOp)(JSContext *cx, JS::HandleObject obj, JS::HandleObject receiver, uint32_t index,
JS::MutableHandleValue vp);
typedef bool
(* StrictGenericIdOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id,
JS::MutableHandleValue vp, bool strict);
typedef bool
(* StrictPropertyIdOp)(JSContext *cx, JS::HandleObject obj, JS::Handle<PropertyName*> name,
JS::MutableHandleValue vp, bool strict);
typedef bool
(* StrictElementIdOp)(JSContext *cx, JS::HandleObject obj, uint32_t index,
JS::MutableHandleValue vp, bool strict);
typedef bool
(* GenericAttributesOp)(JSContext *cx, JS::HandleObject obj, JS::HandleId id, unsigned *attrsp);
typedef bool
(* PropertyAttributesOp)(JSContext *cx, JS::HandleObject obj, JS::Handle<PropertyName*> name,
unsigned *attrsp);
typedef bool
(* DeletePropertyOp)(JSContext *cx, JS::HandleObject obj, JS::Handle<PropertyName*> name,
bool *succeeded);
typedef bool
(* DeleteElementOp)(JSContext *cx, JS::HandleObject obj, uint32_t index, 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);
typedef bool
(* SliceOp)(JSContext *cx, JS::HandleObject obj, uint32_t begin, uint32_t end,
JS::HandleObject result); // result is actually preallocted.
typedef JSObject *
(* ObjectOp)(JSContext *cx, JS::HandleObject obj);
typedef void
(* FinalizeOp)(FreeOp *fop, JSObject *obj);
#define JS_CLASS_MEMBERS(FinalizeOpType) \
const char *name; \
uint32_t flags; \
\
/* Mandatory function pointer members. */ \
JSPropertyOp addProperty; \
JSDeletePropertyOp delProperty; \
JSPropertyOp getProperty; \
JSStrictPropertyOp setProperty; \
JSEnumerateOp enumerate; \
JSResolveOp resolve; \
JSConvertOp convert; \
\
/* Optional members (may be null). */ \
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);
struct ClassSpec
{
ClassObjectCreationOp createConstructor;
ClassObjectCreationOp createPrototype;
const JSFunctionSpec *constructorFunctions;
const JSFunctionSpec *prototypeFunctions;
FinishClassInitOp finishInit;
bool defined() const { return !!createConstructor; }
};
struct ClassExtension
{
JSObjectOp outerObject;
JSObjectOp innerObject;
JSIteratorOp iteratorObject;
/*
* 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;
};
#define JS_NULL_CLASS_SPEC {nullptr,nullptr,nullptr,nullptr,nullptr}
#define JS_NULL_CLASS_EXT {nullptr,nullptr,nullptr,false,nullptr}
struct ObjectOps
{
LookupGenericOp lookupGeneric;
LookupPropOp lookupProperty;
LookupElementOp lookupElement;
DefineGenericOp defineGeneric;
DefinePropOp defineProperty;
DefineElementOp defineElement;
GenericIdOp getGeneric;
PropertyIdOp getProperty;
ElementIdOp getElement;
StrictGenericIdOp setGeneric;
StrictPropertyIdOp setProperty;
StrictElementIdOp setElement;
GenericAttributesOp getGenericAttributes;
GenericAttributesOp setGenericAttributes;
DeletePropertyOp deleteProperty;
DeleteElementOp deleteElement;
WatchOp watch;
UnwatchOp unwatch;
SliceOp slice; // Optimized slice, can be null.
JSNewEnumerateOp enumerate;
ObjectOp thisObject;
};
#define JS_NULL_OBJECT_OPS \
{nullptr,nullptr,nullptr,nullptr,nullptr,nullptr,nullptr,nullptr,nullptr, \
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[31];
};
#define JSCLASS_HAS_PRIVATE (1<<0) // objects have private slot
#define JSCLASS_NEW_ENUMERATE (1<<1) // has JSNewEnumerateOp hook
#define JSCLASS_NEW_RESOLVE (1<<2) // has JSNewResolveOp hook
#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))
// Bit 22 unused.
// 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.
//
#define JSCLASS_GLOBAL_SLOT_COUNT (3 + 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_WIDTH 6
#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;
/* Class is not native and its map is not a scope. */
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 isCallable() const {
return this == js::FunctionClassPtr || 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); }
};
JS_STATIC_ASSERT(offsetof(JSClass, name) == offsetof(Class, name));
JS_STATIC_ASSERT(offsetof(JSClass, flags) == offsetof(Class, flags));
JS_STATIC_ASSERT(offsetof(JSClass, addProperty) == offsetof(Class, addProperty));
JS_STATIC_ASSERT(offsetof(JSClass, delProperty) == offsetof(Class, delProperty));
JS_STATIC_ASSERT(offsetof(JSClass, getProperty) == offsetof(Class, getProperty));
JS_STATIC_ASSERT(offsetof(JSClass, setProperty) == offsetof(Class, setProperty));
JS_STATIC_ASSERT(offsetof(JSClass, enumerate) == offsetof(Class, enumerate));
JS_STATIC_ASSERT(offsetof(JSClass, resolve) == offsetof(Class, resolve));
JS_STATIC_ASSERT(offsetof(JSClass, convert) == offsetof(Class, convert));
JS_STATIC_ASSERT(offsetof(JSClass, finalize) == offsetof(Class, finalize));
JS_STATIC_ASSERT(offsetof(JSClass, call) == offsetof(Class, call));
JS_STATIC_ASSERT(offsetof(JSClass, construct) == offsetof(Class, construct));
JS_STATIC_ASSERT(offsetof(JSClass, hasInstance) == offsetof(Class, hasInstance));
JS_STATIC_ASSERT(offsetof(JSClass, trace) == offsetof(Class, trace));
JS_STATIC_ASSERT(sizeof(JSClass) == sizeof(Class));
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_Array, ESClass_Number, ESClass_String, ESClass_Boolean,
ESClass_RegExp, ESClass_ArrayBuffer, ESClass_Date
};
/*
* 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);
} /* namespace js */
#endif /* js_Class_h */
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