1 files changed, 174 insertions, 0 deletions
diff --git a/js/src/vm/BoundFunctionObject.h b/js/src/vm/BoundFunctionObject.h
new file mode 100644
index 0000000000..566bdc0bed
--- /dev/null
+++ b/js/src/vm/BoundFunctionObject.h
@@ -0,0 +1,174 @@
+/* -*- 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/. */
+
+#ifndef vm_BoundFunctionObject_h
+#define vm_BoundFunctionObject_h
+
+#include "jstypes.h"
+
+#include "gc/Policy.h"
+#include "vm/ArrayObject.h"
+#include "vm/JSAtom.h"
+#include "vm/JSObject.h"
+
+namespace js {
+
+// Implementation of Bound Function Exotic Objects.
+// ES2023 10.4.1
+// https://tc39.es/ecma262/#sec-bound-function-exotic-objects
+class BoundFunctionObject : public NativeObject {
+ public:
+  static const JSClass class_;
+
+  // FlagsSlot uses the low bit for the is-constructor flag and the other bits
+  // for the number of arguments.
+  static constexpr size_t IsConstructorFlag = 0b1;
+  static constexpr size_t NumBoundArgsShift = 1;
+
+  // The maximum number of bound arguments that can be stored inline in
+  // BoundArg*Slot.
+  static constexpr size_t MaxInlineBoundArgs = 3;
+
+ private:
+  enum {
+    // The [[BoundTargetFunction]] (a callable object).
+    TargetSlot,
+
+    // The number of arguments + the is-constructor flag, stored as Int32Value.
+    FlagsSlot,
+
+    // The [[BoundThis]] Value.
+    BoundThisSlot,
+
+    // The [[BoundArguments]]. If numBoundArgs exceeds MaxInlineBoundArgs,
+    // BoundArg0Slot will contain an array object that stores the values and the
+    // other two slots will be unused.
+    BoundArg0Slot,
+    BoundArg1Slot,
+    BoundArg2Slot,
+
+    // Initial slots for the `length` and `name` own data properties. Note that
+    // these properties are configurable, so these slots can be mutated when the
+    // object is exposed to JS.
+    LengthSlot,
+    NameSlot,
+
+    SlotCount
+  };
+
+  // The AllocKind should match SlotCount. See assertion in functionBindImpl.
+  static constexpr gc::AllocKind allocKind = gc::AllocKind::OBJECT8_BACKGROUND;
+
+  void initFlags(size_t numBoundArgs, bool isConstructor) {
+    int32_t val = (numBoundArgs << NumBoundArgsShift) | isConstructor;
+    initReservedSlot(FlagsSlot, Int32Value(val));
+  }
+
+ public:
+  size_t numBoundArgs() const {
+    int32_t v = getReservedSlot(FlagsSlot).toInt32();
+    MOZ_ASSERT(v >= 0);
+    return v >> NumBoundArgsShift;
+  }
+  bool isConstructor() const {
+    int32_t v = getReservedSlot(FlagsSlot).toInt32();
+    return v & IsConstructorFlag;
+  }
+
+  Value getTargetVal() const { return getReservedSlot(TargetSlot); }
+  JSObject* getTarget() const { return &getTargetVal().toObject(); }
+
+  Value getBoundThis() const { return getReservedSlot(BoundThisSlot); }
+
+  Value getInlineBoundArg(size_t i) const {
+    MOZ_ASSERT(i < numBoundArgs());
+    MOZ_ASSERT(numBoundArgs() <= MaxInlineBoundArgs);
+    return getReservedSlot(BoundArg0Slot + i);
+  }
+  ArrayObject* getBoundArgsArray() const {
+    MOZ_ASSERT(numBoundArgs() > MaxInlineBoundArgs);
+    return &getReservedSlot(BoundArg0Slot).toObject().as<ArrayObject>();
+  }
+  Value getBoundArg(size_t i) const {
+    MOZ_ASSERT(i < numBoundArgs());
+    if (numBoundArgs() <= MaxInlineBoundArgs) {
+      return getInlineBoundArg(i);
+    }
+    return getBoundArgsArray()->getDenseElement(i);
+  }
+
+  void initLength(double len) {
+    MOZ_ASSERT(getReservedSlot(LengthSlot).isUndefined());
+    initReservedSlot(LengthSlot, NumberValue(len));
+  }
+  void initName(JSAtom* name) {
+    MOZ_ASSERT(getReservedSlot(NameSlot).isUndefined());
+    initReservedSlot(NameSlot, StringValue(name));
+  }
+
+  // Get the `length` and `name` property values when the object has the
+  // original shape. See comment for LengthSlot and NameSlot.
+  Value getLengthForInitialShape() const { return getReservedSlot(LengthSlot); }
+  Value getNameForInitialShape() const { return getReservedSlot(NameSlot); }
+
+  // The [[Call]] and [[Construct]] hooks.
+  static bool call(JSContext* cx, unsigned argc, Value* vp);
+  static bool construct(JSContext* cx, unsigned argc, Value* vp);
+
+  // The JSFunToStringOp implementation for Function.prototype.toString.
+  static JSString* funToString(JSContext* cx, Handle<JSObject*> obj,
+                               bool isToSource);
+
+  // Implementation of Function.prototype.bind.
+  static bool functionBind(JSContext* cx, unsigned argc, Value* vp);
+
+  static SharedShape* assignInitialShape(JSContext* cx,
+                                         Handle<BoundFunctionObject*> obj);
+
+  static BoundFunctionObject* functionBindImpl(
+      JSContext* cx, Handle<JSObject*> target, Value* args, uint32_t argc,
+      Handle<BoundFunctionObject*> maybeBound);
+
+  static BoundFunctionObject* createWithTemplate(
+      JSContext* cx, Handle<BoundFunctionObject*> templateObj);
+  static BoundFunctionObject* functionBindSpecializedBaseline(
+      JSContext* cx, Handle<JSObject*> target, Value* args, uint32_t argc,
+      Handle<BoundFunctionObject*> templateObj);
+
+  static BoundFunctionObject* createTemplateObject(JSContext* cx);
+
+  bool initTemplateSlotsForSpecializedBind(JSContext* cx, uint32_t numBoundArgs,
+                                           bool targetIsConstructor,
+                                           uint32_t targetLength,
+                                           JSAtom* targetName);
+
+  static constexpr size_t offsetOfTargetSlot() {
+    return getFixedSlotOffset(TargetSlot);
+  }
+  static constexpr size_t offsetOfFlagsSlot() {
+    return getFixedSlotOffset(FlagsSlot);
+  }
+  static constexpr size_t offsetOfBoundThisSlot() {
+    return getFixedSlotOffset(BoundThisSlot);
+  }
+  static constexpr size_t offsetOfFirstInlineBoundArg() {
+    return getFixedSlotOffset(BoundArg0Slot);
+  }
+  static constexpr size_t offsetOfLengthSlot() {
+    return getFixedSlotOffset(LengthSlot);
+  }
+  static constexpr size_t offsetOfNameSlot() {
+    return getFixedSlotOffset(NameSlot);
+  }
+
+  static constexpr size_t targetSlot() { return TargetSlot; }
+  static constexpr size_t boundThisSlot() { return BoundThisSlot; }
+  static constexpr size_t firstInlineBoundArgSlot() { return BoundArg0Slot; }
+};
+
+};  // namespace js
+
+#endif /* vm_BoundFunctionObject_h */