The Tor Browser: js/src/builtin/TypedObject.h@6474c204b198 (annotated)

js/src/builtin/TypedObject.h@6474c204b198 (annotated)

js/src/builtin/TypedObject.h

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- 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/. */
 #ifndef builtin_TypedObject_h
 #define builtin_TypedObject_h
 #include "jsobj.h"
 #include "builtin/TypedObjectConstants.h"
 #include "vm/ArrayBufferObject.h"
 /*
  * -------------
  * Typed Objects
  * -------------
  *
  * Typed objects are a special kind of JS object where the data is
  * given well-structured form. To use a typed object, users first
  * create *type objects* (no relation to the type objects used in TI)
  * that define the type layout. For example, a statement like:
  *
  *    var PointType = new StructType({x: uint8, y: uint8});
  *
  * would create a type object PointType that is a struct with
  * two fields, each of uint8 type.
  *
  * This comment typically assumes familiary with the API.  For more
  * info on the API itself, see the Harmony wiki page at
  * http://wiki.ecmascript.org/doku.php?id=harmony:typed_objects or the
  * ES6 spec (not finalized at the time of this writing).
  *
  * - Initialization:
  *
  * Currently, all "globals" related to typed objects are packaged
  * within a single "module" object `TypedObject`. This module has its
  * own js::Class and when that class is initialized, we also create
  * and define all other values (in `js_InitTypedObjectModuleClass()`).
  *
  * - Type objects, meta type objects, and type representations:
  *
  * There are a number of pre-defined type objects, one for each
  * scalar type (`uint8` etc). Each of these has its own class_,
  * defined in `DefineNumericClass()`.
  *
  * There are also meta type objects (`ArrayType`, `StructType`).
  * These constructors are not themselves type objects but rather the
  * means for the *user* to construct new typed objects.
  *
  * Each type object is associated with a *type representation* (see
  * TypeRepresentation.h). Type representations are canonical versions
  * of type objects. We attach them to TI type objects and (eventually)
  * use them for shape guards etc. They are purely internal to the
  * engine and are not exposed to end users (though self-hosted code
  * sometimes accesses them).
  *
  * - Typed objects:
  *
  * A typed object is an instance of a *type object* (note the past
  * participle). There is one class for *transparent* typed objects and
  * one for *opaque* typed objects. These classes are equivalent in
  * basically every way, except that requesting the backing buffer of
  * an opaque typed object yields null. We use distinct js::Classes to
  * avoid the need for an extra slot in every typed object.
  *
  * Note that whether a typed object is opaque is not directly
  * connected to its type. That is, opaque types are *always*
  * represented by opaque typed objects, but you may have opaque typed
  * objects for transparent types too. This can occur for two reasons:
  * (1) a transparent type may be embedded within an opaque type or (2)
  * users can choose to convert transparent typed objects into opaque
  * ones to avoid giving access to the buffer itself.
  *
  * Typed objects (no matter their class) are non-native objects that
  * fully override the property accessors etc. The overridden accessor
  * methods are the same in each and are defined in methods of
  * TypedObject.
  *
  * Typed objects may be attached or unattached. An unattached typed
  * object has no memory associated with it; it is basically a null
  * pointer. When first created, objects are always attached, but they
  * can become unattached if their buffer is neutered (note that this
  * implies that typed objects of opaque types can never be unattached).
  *
  * When a new typed object instance is created, fresh memory is
  * allocated and set as that typed object's private field. The object
  * is then considered the *owner* of that memory: when the object is
  * collected, its finalizer will free the memory. The fact that an
  * object `o` owns its memory is indicated by setting its reserved
  * slot JS_TYPEDOBJ_SLOT_OWNER to `o` (a trivial cycle, in other
  * words).
  *
  * Later, *derived* typed objects can be created, typically via an
  * access like `o.f` where `f` is some complex (non-scalar) type, but
  * also explicitly via Handle objects. In those cases, the memory
  * pointer of the derived object is set to alias the owner's memory
  * pointer, and the owner slot for the derived object is set to the
  * owner object, thus ensuring that the owner is not collected while
  * the derived object is alive. We always maintain the invariant that
  * JS_TYPEDOBJ_SLOT_OWNER is the true owner of the memory, meaning
  * that there is a shallow tree. This prevents an access pattern like
  * `a.b.c.d` from keeping all the intermediate objects alive.
  */
 namespace js {
 /*
  * Helper method for converting a double into other scalar
  * types in the same way that JavaScript would. In particular,
  * simple C casting from double to int32_t gets things wrong
  * for values like 0xF0000000.
  */
 template <typename T>
 static T ConvertScalar(double d)
 {
     if (TypeIsFloatingPoint<T>()) {
         return T(d);
     } else if (TypeIsUnsigned<T>()) {
         uint32_t n = ToUint32(d);
         return T(n);
     } else {
         int32_t n = ToInt32(d);
         return T(n);
     }
 }
 /*
  * The prototype for a typed object. Currently, carries a link to the
  * type descriptor. Eventually will carry most of the type information
  * we want.
  */
 class TypedProto : public JSObject
 {
   public:
     static const Class class_;
     inline void initTypeDescrSlot(TypeDescr &descr);
     TypeDescr &typeDescr() const {
         return getReservedSlot(JS_TYPROTO_SLOT_DESCR).toObject().as<TypeDescr>();
     }
 };
 class TypeDescr : public JSObject
 {
   public:
     // This is *intentionally* not defined so as to produce link
     // errors if a is<FooTypeDescr>() etc goes wrong. Otherwise, the
     // default implementation resolves this to a reference to
     // FooTypeDescr::class_ which resolves to
     // JSObject::class_. Debugging the resulting errors leads to much
     // fun and rejoicing.
     static const Class class_;
     enum Kind {
         Scalar = JS_TYPEREPR_SCALAR_KIND,
         Reference = JS_TYPEREPR_REFERENCE_KIND,
         X4 = JS_TYPEREPR_X4_KIND,
         Struct = JS_TYPEREPR_STRUCT_KIND,
         SizedArray = JS_TYPEREPR_SIZED_ARRAY_KIND,
         UnsizedArray = JS_TYPEREPR_UNSIZED_ARRAY_KIND,
     };
     static bool isSized(Kind kind) {
         return kind > JS_TYPEREPR_MAX_UNSIZED_KIND;
     }
     JSAtom &stringRepr() const {
         return getReservedSlot(JS_DESCR_SLOT_STRING_REPR).toString()->asAtom();
     }
     TypeDescr::Kind kind() const {
         return (TypeDescr::Kind) getReservedSlot(JS_DESCR_SLOT_KIND).toInt32();
     }
     bool opaque() const {
         return getReservedSlot(JS_DESCR_SLOT_OPAQUE).toBoolean();
     }
     bool transparent() const {
         return !opaque();
     }
     int32_t alignment() {
         return getReservedSlot(JS_DESCR_SLOT_ALIGNMENT).toInt32();
     }
 };
 typedef Handle<TypeDescr*> HandleTypeDescr;
 class SizedTypeDescr : public TypeDescr
 {
   public:
     int32_t size() {
         return getReservedSlot(JS_DESCR_SLOT_SIZE).toInt32();
     }
     void initInstances(const JSRuntime *rt, uint8_t *mem, size_t length);
     void traceInstances(JSTracer *trace, uint8_t *mem, size_t length);
 };
 typedef Handle<SizedTypeDescr*> HandleSizedTypeDescr;
 class SimpleTypeDescr : public SizedTypeDescr
 {
 };
 // Type for scalar type constructors like `uint8`. All such type
 // constructors share a common js::Class and JSFunctionSpec. Scalar
 // types are non-opaque (their storage is visible unless combined with
 // an opaque reference type.)
 class ScalarTypeDescr : public SimpleTypeDescr
 {
   public:
     // Must match order of JS_FOR_EACH_SCALAR_TYPE_REPR below
     enum Type {
         TYPE_INT8 = JS_SCALARTYPEREPR_INT8,
         TYPE_UINT8 = JS_SCALARTYPEREPR_UINT8,
         TYPE_INT16 = JS_SCALARTYPEREPR_INT16,
         TYPE_UINT16 = JS_SCALARTYPEREPR_UINT16,
         TYPE_INT32 = JS_SCALARTYPEREPR_INT32,
         TYPE_UINT32 = JS_SCALARTYPEREPR_UINT32,
         TYPE_FLOAT32 = JS_SCALARTYPEREPR_FLOAT32,
         TYPE_FLOAT64 = JS_SCALARTYPEREPR_FLOAT64,
         /*
          * Special type that's a uint8_t, but assignments are clamped to 0 .. 255.
          * Treat the raw data type as a uint8_t.
          */
         TYPE_UINT8_CLAMPED = JS_SCALARTYPEREPR_UINT8_CLAMPED,
     };
     static const int32_t TYPE_MAX = TYPE_UINT8_CLAMPED + 1;
     static const TypeDescr::Kind Kind = TypeDescr::Scalar;
     static const bool Opaque = false;
     static int32_t size(Type t);
     static int32_t alignment(Type t);
     static const char *typeName(Type type);
     static const Class class_;
     static const JSFunctionSpec typeObjectMethods[];
     ScalarTypeDescr::Type type() const {
         return (ScalarTypeDescr::Type) getReservedSlot(JS_DESCR_SLOT_TYPE).toInt32();
     }
     static bool call(JSContext *cx, unsigned argc, Value *vp);
 };
 // Enumerates the cases of ScalarTypeDescr::Type which have
 // unique C representation. In particular, omits Uint8Clamped since it
 // is just a Uint8.
 #define JS_FOR_EACH_UNIQUE_SCALAR_TYPE_REPR_CTYPE(macro_)                     \
     macro_(ScalarTypeDescr::TYPE_INT8,    int8_t,   int8)            \
     macro_(ScalarTypeDescr::TYPE_UINT8,   uint8_t,  uint8)           \
     macro_(ScalarTypeDescr::TYPE_INT16,   int16_t,  int16)           \
     macro_(ScalarTypeDescr::TYPE_UINT16,  uint16_t, uint16)          \
     macro_(ScalarTypeDescr::TYPE_INT32,   int32_t,  int32)           \
     macro_(ScalarTypeDescr::TYPE_UINT32,  uint32_t, uint32)          \
     macro_(ScalarTypeDescr::TYPE_FLOAT32, float,    float32)         \
     macro_(ScalarTypeDescr::TYPE_FLOAT64, double,   float64)
 // Must be in same order as the enum ScalarTypeDescr::Type:
 #define JS_FOR_EACH_SCALAR_TYPE_REPR(macro_)                                    \
     JS_FOR_EACH_UNIQUE_SCALAR_TYPE_REPR_CTYPE(macro_)                           \
     macro_(ScalarTypeDescr::TYPE_UINT8_CLAMPED, uint8_t, uint8Clamped)
 // Type for reference type constructors like `Any`, `String`, and
 // `Object`. All such type constructors share a common js::Class and
 // JSFunctionSpec. All these types are opaque.
 class ReferenceTypeDescr : public SimpleTypeDescr
 {
   public:
     // Must match order of JS_FOR_EACH_REFERENCE_TYPE_REPR below
     enum Type {
         TYPE_ANY = JS_REFERENCETYPEREPR_ANY,
         TYPE_OBJECT = JS_REFERENCETYPEREPR_OBJECT,
         TYPE_STRING = JS_REFERENCETYPEREPR_STRING,
     };
     static const int32_t TYPE_MAX = TYPE_STRING + 1;
     static const char *typeName(Type type);
     static const TypeDescr::Kind Kind = TypeDescr::Reference;
     static const bool Opaque = true;
     static const Class class_;
     static int32_t size(Type t);
     static int32_t alignment(Type t);
     static const JSFunctionSpec typeObjectMethods[];
     ReferenceTypeDescr::Type type() const {
         return (ReferenceTypeDescr::Type) getReservedSlot(JS_DESCR_SLOT_TYPE).toInt32();
     }
     const char *typeName() const {
         return typeName(type());
     }
     static bool call(JSContext *cx, unsigned argc, Value *vp);
 };
 #define JS_FOR_EACH_REFERENCE_TYPE_REPR(macro_)                    \
     macro_(ReferenceTypeDescr::TYPE_ANY,    HeapValue, Any)        \
     macro_(ReferenceTypeDescr::TYPE_OBJECT, HeapPtrObject, Object) \
     macro_(ReferenceTypeDescr::TYPE_STRING, HeapPtrString, string)
 // Type descriptors whose instances are objects and hence which have
 // an associated `prototype` property.
 class ComplexTypeDescr : public SizedTypeDescr
 {
   public:
     // Returns the prototype that instances of this type descriptor
     // will have.
     TypedProto &instancePrototype() const {
         return getReservedSlot(JS_DESCR_SLOT_TYPROTO).toObject().as<TypedProto>();
     }
 };
 /*
  * Type descriptors `float32x4` and `int32x4`
  */
 class X4TypeDescr : public ComplexTypeDescr
 {
   public:
     enum Type {
         TYPE_INT32 = JS_X4TYPEREPR_INT32,
         TYPE_FLOAT32 = JS_X4TYPEREPR_FLOAT32,
     };
     static const TypeDescr::Kind Kind = TypeDescr::X4;
     static const bool Opaque = false;
     static const Class class_;
     static int32_t size(Type t);
     static int32_t alignment(Type t);
     X4TypeDescr::Type type() const {
         return (X4TypeDescr::Type) getReservedSlot(JS_DESCR_SLOT_TYPE).toInt32();
     }
     static bool call(JSContext *cx, unsigned argc, Value *vp);
     static bool is(const Value &v);
 };
 #define JS_FOR_EACH_X4_TYPE_REPR(macro_)                             \
     macro_(X4TypeDescr::TYPE_INT32, int32_t, int32)                  \
     macro_(X4TypeDescr::TYPE_FLOAT32, float, float32)
 bool IsTypedObjectClass(const Class *clasp); // Defined below
 bool IsTypedObjectArray(JSObject& obj);
 bool CreateUserSizeAndAlignmentProperties(JSContext *cx, HandleTypeDescr obj);
 /*
  * Properties and methods of the `ArrayType` meta type object. There
  * is no `class_` field because `ArrayType` is just a native
  * constructor function.
  */
 class ArrayMetaTypeDescr : public JSObject
 {
   private:
     friend class UnsizedArrayTypeDescr;
     // Helper for creating a new ArrayType object, either sized or unsized.
     // The template parameter `T` should be either `UnsizedArrayTypeDescr`
     // or `SizedArrayTypeDescr`.
     //
     // - `arrayTypePrototype` - prototype for the new object to be created,
     //                          either ArrayType.prototype or
     //                          unsizedArrayType.__proto__ depending on
     //                          whether this is a sized or unsized array
     // - `elementType` - type object for the elements in the array
     // - `stringRepr` - canonical string representation for the array
     // - `size` - length of the array (0 if unsized)
     template<class T>
     static T *create(JSContext *cx,
                      HandleObject arrayTypePrototype,
                      HandleSizedTypeDescr elementType,
                      HandleAtom stringRepr,
                      int32_t size);
   public:
     // Properties and methods to be installed on ArrayType.prototype,
     // and hence inherited by all array type objects:
     static const JSPropertySpec typeObjectProperties[];
     static const JSFunctionSpec typeObjectMethods[];
     // Properties and methods to be installed on ArrayType.prototype.prototype,
     // and hence inherited by all array *typed* objects:
     static const JSPropertySpec typedObjectProperties[];
     static const JSFunctionSpec typedObjectMethods[];
     // This is the function that gets called when the user
     // does `new ArrayType(elem)`. It produces an array type object.
     static bool construct(JSContext *cx, unsigned argc, Value *vp);
 };
 /*
  * Type descriptor created by `new ArrayType(typeObj)`
  *
  * These have a prototype, and hence *could* be a subclass of
  * `ComplexTypeDescr`, but it would require some reshuffling of the
  * hierarchy, and it's not worth the trouble since they will be going
  * away as part of bug 973238.
  */
 class UnsizedArrayTypeDescr : public TypeDescr
 {
   public:
     static const Class class_;
     static const TypeDescr::Kind Kind = TypeDescr::UnsizedArray;
     // This is the sized method on unsized array type objects.  It
     // produces a sized variant.
     static bool dimension(JSContext *cx, unsigned int argc, jsval *vp);
     SizedTypeDescr &elementType() {
         return getReservedSlot(JS_DESCR_SLOT_ARRAY_ELEM_TYPE).toObject().as<SizedTypeDescr>();
     }
 };
 /*
  * Type descriptor created by `unsizedArrayTypeObj.dimension()`
  */
 class SizedArrayTypeDescr : public ComplexTypeDescr
 {
   public:
     static const Class class_;
     static const TypeDescr::Kind Kind = TypeDescr::SizedArray;
     SizedTypeDescr &elementType() {
         return getReservedSlot(JS_DESCR_SLOT_ARRAY_ELEM_TYPE).toObject().as<SizedTypeDescr>();
     }
     int32_t length() {
         return getReservedSlot(JS_DESCR_SLOT_SIZED_ARRAY_LENGTH).toInt32();
     }
 };
 /*
  * Properties and methods of the `StructType` meta type object. There
  * is no `class_` field because `StructType` is just a native
  * constructor function.
  */
 class StructMetaTypeDescr : public JSObject
 {
   private:
     static JSObject *create(JSContext *cx, HandleObject structTypeGlobal,
                             HandleObject fields);
   public:
     // Properties and methods to be installed on StructType.prototype,
     // and hence inherited by all struct type objects:
     static const JSPropertySpec typeObjectProperties[];
     static const JSFunctionSpec typeObjectMethods[];
     // Properties and methods to be installed on StructType.prototype.prototype,
     // and hence inherited by all struct *typed* objects:
     static const JSPropertySpec typedObjectProperties[];
     static const JSFunctionSpec typedObjectMethods[];
     // This is the function that gets called when the user
     // does `new StructType(...)`. It produces a struct type object.
     static bool construct(JSContext *cx, unsigned argc, Value *vp);
 };
 class StructTypeDescr : public ComplexTypeDescr
 {
   public:
     static const Class class_;
     // Returns the number of fields defined in this struct.
     size_t fieldCount();
     // Set `*out` to the index of the field named `id` and returns true,
     // or return false if no such field exists.
     bool fieldIndex(jsid id, size_t *out);
     // Return the name of the field at index `index`.
     JSAtom &fieldName(size_t index);
     // Return the type descr of the field at index `index`.
     SizedTypeDescr &fieldDescr(size_t index);
     // Return the offset of the field at index `index`.
     int32_t fieldOffset(size_t index);
 };
 typedef Handle<StructTypeDescr*> HandleStructTypeDescr;
 /*
  * This object exists in order to encapsulate the typed object types
  * somewhat, rather than sticking them all into the global object.
  * Eventually it will go away and become a module.
  */
 class TypedObjectModuleObject : public JSObject {
   public:
     enum Slot {
         ArrayTypePrototype,
         StructTypePrototype,
         SlotCount
     };
     static const Class class_;
 };
 /*
  * Base type for typed objects and handles. Basically any type whose
  * contents consist of typed memory.
  */
 class TypedObject : public ArrayBufferViewObject
 {
   private:
     static const bool IsTypedObjectClass = true;
     template<class T>
     static bool obj_getArrayElement(JSContext *cx,
                                     Handle<TypedObject*> typedObj,
                                     Handle<TypeDescr*> typeDescr,
                                     uint32_t index,
                                     MutableHandleValue vp);
     template<class T>
     static bool obj_setArrayElement(JSContext *cx,
                                     Handle<TypedObject*> typedObj,
                                     Handle<TypeDescr*> typeDescr,
                                     uint32_t index,
                                     MutableHandleValue vp);
   protected:
     static void obj_trace(JSTracer *trace, JSObject *object);
     static bool obj_lookupGeneric(JSContext *cx, HandleObject obj,
                                   HandleId id, MutableHandleObject objp,
                                   MutableHandleShape propp);
     static bool obj_lookupProperty(JSContext *cx, HandleObject obj,
                                    HandlePropertyName name,
                                    MutableHandleObject objp,
                                    MutableHandleShape propp);
     static bool obj_lookupElement(JSContext *cx, HandleObject obj,
                                   uint32_t index, MutableHandleObject objp,
                                   MutableHandleShape propp);
     static bool obj_defineGeneric(JSContext *cx, HandleObject obj, HandleId id, HandleValue v,
                                   PropertyOp getter, StrictPropertyOp setter, unsigned attrs);
     static bool obj_defineProperty(JSContext *cx, HandleObject obj,
                                    HandlePropertyName name, HandleValue v,
                                    PropertyOp getter, StrictPropertyOp setter, unsigned attrs);
     static bool obj_defineElement(JSContext *cx, HandleObject obj, uint32_t index, HandleValue v,
                                   PropertyOp getter, StrictPropertyOp setter, unsigned attrs);
     static bool obj_getGeneric(JSContext *cx, HandleObject obj, HandleObject receiver,
                                HandleId id, MutableHandleValue vp);
     static bool obj_getProperty(JSContext *cx, HandleObject obj, HandleObject receiver,
                                 HandlePropertyName name, MutableHandleValue vp);
     static bool obj_getElement(JSContext *cx, HandleObject obj, HandleObject receiver,
                                uint32_t index, MutableHandleValue vp);
     static bool obj_getUnsizedArrayElement(JSContext *cx, HandleObject obj, HandleObject receiver,
                                          uint32_t index, MutableHandleValue vp);
     static bool obj_setGeneric(JSContext *cx, HandleObject obj, HandleId id,
                                MutableHandleValue vp, bool strict);
     static bool obj_setProperty(JSContext *cx, HandleObject obj, HandlePropertyName name,
                                 MutableHandleValue vp, bool strict);
     static bool obj_setElement(JSContext *cx, HandleObject obj, uint32_t index,
                                MutableHandleValue vp, bool strict);
     static bool obj_getGenericAttributes(JSContext *cx, HandleObject obj,
                                          HandleId id, unsigned *attrsp);
     static bool obj_setGenericAttributes(JSContext *cx, HandleObject obj,
                                          HandleId id, unsigned *attrsp);
     static bool obj_deleteProperty(JSContext *cx, HandleObject obj, HandlePropertyName name,
                                    bool *succeeded);
     static bool obj_deleteElement(JSContext *cx, HandleObject obj, uint32_t index,
                                   bool *succeeded);
     static bool obj_enumerate(JSContext *cx, HandleObject obj, JSIterateOp enum_op,
                               MutableHandleValue statep, MutableHandleId idp);
   public:
     static size_t offsetOfOwnerSlot();
     // Each typed object contains a void* pointer pointing at the
     // binary data that it represents. (That data may be owned by this
     // object or this object may alias data owned by someone else.)
     // This function returns the offset in bytes within the object
     // where the `void*` pointer can be found. It is intended for use
     // by the JIT.
     static size_t offsetOfDataSlot();
     // Offset of the byte offset slot.
     static size_t offsetOfByteOffsetSlot();
     // Helper for createUnattached()
     static TypedObject *createUnattachedWithClass(JSContext *cx,
                                                  const Class *clasp,
                                                  HandleTypeDescr type,
                                                  int32_t length);
     // Creates an unattached typed object or handle (depending on the
     // type parameter T). Note that it is only legal for unattached
     // handles to escape to the end user; for non-handles, the caller
     // should always invoke one of the `attach()` methods below.
     //
     // Arguments:
     // - type: type object for resulting object
     // - length: 0 unless this is an array, otherwise the length
     static TypedObject *createUnattached(JSContext *cx, HandleTypeDescr type,
                                         int32_t length);
     // Creates a typedObj that aliases the memory pointed at by `owner`
     // at the given offset. The typedObj will be a handle iff type is a
     // handle and a typed object otherwise.
     static TypedObject *createDerived(JSContext *cx,
                                       HandleSizedTypeDescr type,
                                       Handle<TypedObject*> typedContents,
                                       int32_t offset);
     // Creates a new typed object whose memory is freshly allocated
     // and initialized with zeroes (or, in the case of references, an
     // appropriate default value).
     static TypedObject *createZeroed(JSContext *cx,
                                      HandleTypeDescr typeObj,
                                      int32_t length);
     // User-accessible constructor (`new TypeDescriptor(...)`)
     // used for sized types. Note that the callee here is the *type descriptor*,
     // not the typedObj.
     static bool constructSized(JSContext *cx, unsigned argc, Value *vp);
     // As `constructSized`, but for unsized array types.
     static bool constructUnsized(JSContext *cx, unsigned argc, Value *vp);
     // Use this method when `buffer` is the owner of the memory.
     void attach(ArrayBufferObject &buffer, int32_t offset);
     // Otherwise, use this to attach to memory referenced by another typedObj.
     void attach(TypedObject &typedObj, int32_t offset);
     // Invoked when array buffer is transferred elsewhere
     void neuter(void *newData);
     int32_t offset() const {
         return getReservedSlot(JS_TYPEDOBJ_SLOT_BYTEOFFSET).toInt32();
     }
     ArrayBufferObject &owner() const {
         return getReservedSlot(JS_TYPEDOBJ_SLOT_OWNER).toObject().as<ArrayBufferObject>();
     }
     TypeDescr &typeDescr() const {
         return getReservedSlot(JS_TYPEDOBJ_SLOT_TYPE_DESCR).toObject().as<TypeDescr>();
     }
     uint8_t *typedMem() const {
         return (uint8_t*) getPrivate();
     }
     int32_t byteLength() const {
         return getReservedSlot(JS_TYPEDOBJ_SLOT_BYTELENGTH).toInt32();
     }
     int32_t length() const {
         return getReservedSlot(JS_TYPEDOBJ_SLOT_LENGTH).toInt32();
     }
     int32_t size() const {
         switch (typeDescr().kind()) {
           case TypeDescr::Scalar:
           case TypeDescr::X4:
           case TypeDescr::Reference:
           case TypeDescr::Struct:
           case TypeDescr::SizedArray:
             return typeDescr().as<SizedTypeDescr>().size();
           case TypeDescr::UnsizedArray: {
             SizedTypeDescr &elementType = typeDescr().as<UnsizedArrayTypeDescr>().elementType();
             return elementType.size() * length();
           }
         }
         MOZ_ASSUME_UNREACHABLE("unhandled typerepresentation kind");
     }
     uint8_t *typedMem(size_t offset) const {
         // It seems a bit surprising that one might request an offset
         // == size(), but it can happen when taking the "address of" a
         // 0-sized value. (In other words, we maintain the invariant
         // that `offset + size <= size()` -- this is always checked in
         // the caller's side.)
         JS_ASSERT(offset <= (size_t) size());
         return typedMem() + offset;
     }
 };
 typedef Handle<TypedObject*> HandleTypedObject;
 class TransparentTypedObject : public TypedObject
 {
   public:
     static const Class class_;
 };
 typedef Handle<TransparentTypedObject*> HandleTransparentTypedObject;
 class OpaqueTypedObject : public TypedObject
 {
   public:
     static const Class class_;
     static const JSFunctionSpec handleStaticMethods[];
 };
 /*
  * Usage: NewOpaqueTypedObject(typeObj)
  *
  * Constructs a new, unattached instance of `Handle`.
  */
 bool NewOpaqueTypedObject(JSContext *cx, unsigned argc, Value *vp);
 /*
  * Usage: NewDerivedTypedObject(typeObj, owner, offset)
  *
  * Constructs a new, unattached instance of `Handle`.
  */
 bool NewDerivedTypedObject(JSContext *cx, unsigned argc, Value *vp);
 /*
  * Usage: AttachTypedObject(typedObj, newDatum, newOffset)
  *
  * Moves `typedObj` to point at the memory referenced by `newDatum` with
  * the offset `newOffset`.
  */
 bool AttachTypedObject(ThreadSafeContext *cx, unsigned argc, Value *vp);
 extern const JSJitInfo AttachTypedObjectJitInfo;
 /*
  * Usage: SetTypedObjectOffset(typedObj, offset)
  *
  * Changes the offset for `typedObj` within its buffer to `offset`.
  * `typedObj` must already be attached.
  */
 bool intrinsic_SetTypedObjectOffset(JSContext *cx, unsigned argc, Value *vp);
 bool SetTypedObjectOffset(ThreadSafeContext *, unsigned argc, Value *vp);
 extern const JSJitInfo intrinsic_SetTypedObjectOffsetJitInfo;
 /*
  * Usage: ObjectIsTypeDescr(obj)
  *
  * True if `obj` is a type object.
  */
 bool ObjectIsTypeDescr(ThreadSafeContext *cx, unsigned argc, Value *vp);
 extern const JSJitInfo ObjectIsTypeDescrJitInfo;
 /*
  * Usage: ObjectIsTypedObject(obj)
  *
  * True if `obj` is a transparent or opaque typed object.
  */
 bool ObjectIsTypedObject(ThreadSafeContext *cx, unsigned argc, Value *vp);
 extern const JSJitInfo ObjectIsTypedObjectJitInfo;
 /*
  * Usage: ObjectIsOpaqueTypedObject(obj)
  *
  * True if `obj` is an opaque typed object.
  */
 bool ObjectIsOpaqueTypedObject(ThreadSafeContext *cx, unsigned argc, Value *vp);
 extern const JSJitInfo ObjectIsOpaqueTypedObjectJitInfo;
 /*
  * Usage: ObjectIsTransparentTypedObject(obj)
  *
  * True if `obj` is a transparent typed object.
  */
 bool ObjectIsTransparentTypedObject(ThreadSafeContext *cx, unsigned argc, Value *vp);
 extern const JSJitInfo ObjectIsTransparentTypedObjectJitInfo;
 /* Predicates on type descriptor objects.  In all cases, 'obj' must be a type descriptor. */
 bool TypeDescrIsSimpleType(ThreadSafeContext *, unsigned argc, Value *vp);
 extern const JSJitInfo TypeDescrIsSimpleTypeJitInfo;
 bool TypeDescrIsArrayType(ThreadSafeContext *, unsigned argc, Value *vp);
 extern const JSJitInfo TypeDescrIsArrayTypeJitInfo;
 bool TypeDescrIsSizedArrayType(ThreadSafeContext *, unsigned argc, Value *vp);
 extern const JSJitInfo TypeDescrIsSizedArrayTypeJitInfo;
 bool TypeDescrIsUnsizedArrayType(ThreadSafeContext *, unsigned argc, Value *vp);
 extern const JSJitInfo TypeDescrIsUnsizedArrayTypeJitInfo;
 /*
  * Usage: TypedObjectIsAttached(obj)
  *
  * Given a TypedObject `obj`, returns true if `obj` is
  * "attached" (i.e., its data pointer is nullptr).
  */
 bool TypedObjectIsAttached(ThreadSafeContext *cx, unsigned argc, Value *vp);
 extern const JSJitInfo TypedObjectIsAttachedJitInfo;
 /*
  * Usage: ClampToUint8(v)
  *
  * Same as the C function ClampDoubleToUint8. `v` must be a number.
  */
 bool ClampToUint8(ThreadSafeContext *cx, unsigned argc, Value *vp);
 extern const JSJitInfo ClampToUint8JitInfo;
 /*
  * Usage: Memcpy(targetDatum, targetOffset,
  *               sourceDatum, sourceOffset,
  *               size)
  *
  * Intrinsic function. Copies size bytes from the data for
  * `sourceDatum` at `sourceOffset` into the data for
  * `targetDatum` at `targetOffset`.
  *
  * Both `sourceDatum` and `targetDatum` must be attached.
  */
 bool Memcpy(ThreadSafeContext *cx, unsigned argc, Value *vp);
 extern const JSJitInfo MemcpyJitInfo;
 /*
  * Usage: GetTypedObjectModule()
  *
  * Returns the global "typed object" module, which provides access
  * to the various builtin type descriptors. These are currently
  * exported as immutable properties so it is safe for self-hosted code
  * to access them; eventually this should be linked into the module
  * system.
  */
 bool GetTypedObjectModule(JSContext *cx, unsigned argc, Value *vp);
 /*
  * Usage: GetFloat32x4TypeDescr()
  *
  * Returns the float32x4 type object. SIMD pseudo-module must have
  * been initialized for this to be safe.
  */
 bool GetFloat32x4TypeDescr(JSContext *cx, unsigned argc, Value *vp);
 /*
  * Usage: GetInt32x4TypeDescr()
  *
  * Returns the int32x4 type object. SIMD pseudo-module must have
  * been initialized for this to be safe.
  */
 bool GetInt32x4TypeDescr(JSContext *cx, unsigned argc, Value *vp);
 /*
  * Usage: Store_int8(targetDatum, targetOffset, value)
  *        ...
  *        Store_uint8(targetDatum, targetOffset, value)
  *        ...
  *        Store_float32(targetDatum, targetOffset, value)
  *        Store_float64(targetDatum, targetOffset, value)
  *
  * Intrinsic function. Stores `value` into the memory referenced by
  * `targetDatum` at the offset `targetOffset`.
  *
  * Assumes (and asserts) that:
  * - `targetDatum` is attached
  * - `targetOffset` is a valid offset within the bounds of `targetDatum`
  * - `value` is a number
  */
 #define JS_STORE_SCALAR_CLASS_DEFN(_constant, T, _name)                       \
 class StoreScalar##T {                                                        \
   public:                                                                     \
     static bool Func(ThreadSafeContext *cx, unsigned argc, Value *vp);        \
     static const JSJitInfo JitInfo;                                           \
 };
 /*
  * Usage: Store_Any(targetDatum, targetOffset, value)
  *        Store_Object(targetDatum, targetOffset, value)
  *        Store_string(targetDatum, targetOffset, value)
  *
  * Intrinsic function. Stores `value` into the memory referenced by
  * `targetDatum` at the offset `targetOffset`.
  *
  * Assumes (and asserts) that:
  * - `targetDatum` is attached
  * - `targetOffset` is a valid offset within the bounds of `targetDatum`
  * - `value` is an object (`Store_Object`) or string (`Store_string`).
  */
 #define JS_STORE_REFERENCE_CLASS_DEFN(_constant, T, _name)                    \
 class StoreReference##T {                                                     \
   private:                                                                    \
     static void store(T* heap, const Value &v);                               \
                                                                               \
   public:                                                                     \
     static bool Func(ThreadSafeContext *cx, unsigned argc, Value *vp);        \
     static const JSJitInfo JitInfo;                                           \
 };
 /*
  * Usage: LoadScalar(targetDatum, targetOffset, value)
  *
  * Intrinsic function. Loads value (which must be an int32 or uint32)
  * by `scalarTypeRepr` (which must be a type repr obj) and loads the
  * value at the memory for `targetDatum` at offset `targetOffset`.
  * `targetDatum` must be attached.
  */
 #define JS_LOAD_SCALAR_CLASS_DEFN(_constant, T, _name)                        \
 class LoadScalar##T {                                                         \
   public:                                                                     \
     static bool Func(ThreadSafeContext *cx, unsigned argc, Value *vp);        \
     static const JSJitInfo JitInfo;                                           \
 };
 /*
  * Usage: LoadReference(targetDatum, targetOffset, value)
  *
  * Intrinsic function. Stores value (which must be an int32 or uint32)
  * by `scalarTypeRepr` (which must be a type repr obj) and stores the
  * value at the memory for `targetDatum` at offset `targetOffset`.
  * `targetDatum` must be attached.
  */
 #define JS_LOAD_REFERENCE_CLASS_DEFN(_constant, T, _name)                     \
 class LoadReference##T {                                                      \
   private:                                                                    \
     static void load(T* heap, MutableHandleValue v);                          \
                                                                               \
   public:                                                                     \
     static bool Func(ThreadSafeContext *cx, unsigned argc, Value *vp);        \
     static const JSJitInfo JitInfo;                                           \
 };
 // I was using templates for this stuff instead of macros, but ran
 // into problems with the Unagi compiler.
 JS_FOR_EACH_UNIQUE_SCALAR_TYPE_REPR_CTYPE(JS_STORE_SCALAR_CLASS_DEFN)
 JS_FOR_EACH_UNIQUE_SCALAR_TYPE_REPR_CTYPE(JS_LOAD_SCALAR_CLASS_DEFN)
 JS_FOR_EACH_REFERENCE_TYPE_REPR(JS_STORE_REFERENCE_CLASS_DEFN)
 JS_FOR_EACH_REFERENCE_TYPE_REPR(JS_LOAD_REFERENCE_CLASS_DEFN)
 inline bool
 IsTypedObjectClass(const Class *class_)
 {
     return class_ == &TransparentTypedObject::class_ ||
            class_ == &OpaqueTypedObject::class_;
 }
 inline bool
 IsSimpleTypeDescrClass(const Class* clasp)
 {
     return clasp == &ScalarTypeDescr::class_ ||
            clasp == &ReferenceTypeDescr::class_;
 }
 inline bool
 IsComplexTypeDescrClass(const Class* clasp)
 {
     return clasp == &StructTypeDescr::class_ ||
            clasp == &SizedArrayTypeDescr::class_ ||
            clasp == &X4TypeDescr::class_;
 }
 inline bool
 IsSizedTypeDescrClass(const Class* clasp)
 {
     return IsSimpleTypeDescrClass(clasp) ||
            IsComplexTypeDescrClass(clasp);
 }
 inline bool
 IsTypeDescrClass(const Class* clasp)
 {
     return IsSizedTypeDescrClass(clasp) ||
            clasp == &UnsizedArrayTypeDescr::class_;
 }
 } // namespace js
 JSObject *
 js_InitTypedObjectModuleObject(JSContext *cx, JS::HandleObject obj);
 template <>
 inline bool
 JSObject::is<js::SimpleTypeDescr>() const
 {
     return IsSimpleTypeDescrClass(getClass());
 }
 template <>
 inline bool
 JSObject::is<js::SizedTypeDescr>() const
 {
     return IsSizedTypeDescrClass(getClass());
 }
 template <>
 inline bool
 JSObject::is<js::ComplexTypeDescr>() const
 {
     return IsComplexTypeDescrClass(getClass());
 }
 template <>
 inline bool
 JSObject::is<js::TypeDescr>() const
 {
     return IsTypeDescrClass(getClass());
 }
 template <>
 inline bool
 JSObject::is<js::TypedObject>() const
 {
     return IsTypedObjectClass(getClass());
 }
 template<>
 inline bool
 JSObject::is<js::SizedArrayTypeDescr>() const
 {
     return getClass() == &js::SizedArrayTypeDescr::class_;
 }
 template<>
 inline bool
 JSObject::is<js::UnsizedArrayTypeDescr>() const
 {
     return getClass() == &js::UnsizedArrayTypeDescr::class_;
 }
 inline void
 js::TypedProto::initTypeDescrSlot(TypeDescr &descr)
 {
     initReservedSlot(JS_TYPROTO_SLOT_DESCR, ObjectValue(descr));
 }
 #endif /* builtin_TypedObject_h */

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js/src/builtin/TypedObject.h