js/src/vm/ArrayObject.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: set ts=8 sts=2 et sw=2 tw=80:
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef vm_ArrayObject_h
   8 #define vm_ArrayObject_h
   9
  10 #include "vm/NativeObject.h"
  11
  12 namespace js {
  13
  14 class AutoSetNewObjectMetadata;
  15
  16 class ArrayObject : public NativeObject {
  17  public:
  18   // Array(x) eagerly allocates dense elements if x <= this value. Without
  19   // the subtraction the max would roll over to the next power-of-two (4096)
  20   // due to the way that growElements() and goodAllocated() work.
  21   static const uint32_t EagerAllocationMaxLength =
  22       2048 - ObjectElements::VALUES_PER_HEADER;
  23
  24   static const JSClass class_;
  25
  26   bool lengthIsWritable() const {
  27     return !getElementsHeader()->hasNonwritableArrayLength();
  28   }
  29
  30   uint32_t length() const { return getElementsHeader()->length; }
  31
  32   void setNonWritableLength(JSContext* cx) {
  33     shrinkCapacityToInitializedLength(cx);
  34     getElementsHeader()->setNonwritableArrayLength();
  35   }
  36
  37   void setLength(uint32_t length) {
  38     MOZ_ASSERT(lengthIsWritable());
  39     MOZ_ASSERT_IF(length != getElementsHeader()->length,
  40                   !denseElementsAreFrozen());
  41     getElementsHeader()->length = length;
  42   }
  43
  44   // Try to add a new dense element to this array. The array must be extensible.
  45   //
  46   // Returns DenseElementResult::Incomplete if `index >= length`, if the array
  47   // has sparse elements, if we're adding a sparse element, or if the array
  48   // already contains a dense element at this index.
  49   inline DenseElementResult addDenseElementNoLengthChange(JSContext* cx,
  50                                                           uint32_t index,
  51                                                           const Value& val);
  52
  53   // Make an array object with the specified initial state.
  54   static MOZ_ALWAYS_INLINE ArrayObject* create(
  55       JSContext* cx, gc::AllocKind kind, gc::Heap heap,
  56       Handle<SharedShape*> shape, uint32_t length, uint32_t slotSpan,
  57       AutoSetNewObjectMetadata& metadata, gc::AllocSite* site = nullptr);
  58 };
  59
  60 }  // namespace js
  61
  62 #endif  // vm_ArrayObject_h