StringObject.h

/* -*- 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_StringObject_h
#define vm_StringObject_h

#include "builtin/String.h"

#include "vm/JSObject.h"
#include "vm/Shape.h"

namespace js {

class GlobalObject;

class StringObject : public NativeObject {
  static const unsigned PRIMITIVE_VALUE_SLOT = 0;
  static const unsigned LENGTH_SLOT = 1;

 public:
  static const unsigned RESERVED_SLOTS = 2;

  static const Class class_;

  /*
   * Creates a new String object boxing the given string.  The object's
   * [[Prototype]] is determined from context.
   */
  static inline StringObject* create(JSContext* cx, HandleString str,
                                     HandleObject proto = nullptr,
                                     NewObjectKind newKind = GenericObject);

  /*
   * Compute the initial shape to associate with fresh String objects, which
   * encodes the initial length property. Return the shape after changing
   * |obj|'s last property to it.
   */
  static Shape* assignInitialShape(JSContext* cx, Handle<StringObject*> obj);

  JSString* unbox() const {
    return getFixedSlot(PRIMITIVE_VALUE_SLOT).toString();
  }

  inline size_t length() const {
    return size_t(getFixedSlot(LENGTH_SLOT).toInt32());
  }

  static size_t offsetOfPrimitiveValue() {
    return getFixedSlotOffset(PRIMITIVE_VALUE_SLOT);
  }
  static size_t offsetOfLength() { return getFixedSlotOffset(LENGTH_SLOT); }

 private:
  static inline bool init(JSContext* cx, Handle<StringObject*> obj,
                          HandleString str);

  void setStringThis(JSString* str) {
    MOZ_ASSERT(getReservedSlot(PRIMITIVE_VALUE_SLOT).isUndefined());
    setFixedSlot(PRIMITIVE_VALUE_SLOT, StringValue(str));
    setFixedSlot(LENGTH_SLOT, Int32Value(int32_t(str->length())));
  }

  /* For access to init, as String.prototype is special. */
  friend JSObject* js::InitStringClass(JSContext* cx,
                                       Handle<GlobalObject*> global);
};

}  // namespace js

#endif /* vm_StringObject_h */