1 files changed, 67 insertions, 0 deletions
diff --git a/layout/base/nsPresArena.h b/layout/base/nsPresArena.h
new file mode 100644
index 0000000000..884f2b44c5
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+++ b/layout/base/nsPresArena.h
@@ -0,0 +1,67 @@
+/* -*- 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/.
+ */
+
+/* arena allocation for the frame tree and closely-related objects */
+
+#ifndef nsPresArena_h___
+#define nsPresArena_h___
+
+#include "mozilla/ArenaAllocator.h"
+#include "mozilla/ArenaObjectID.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/MemoryChecking.h"  // Note: Do not remove this, needed for MOZ_HAVE_MEM_CHECKS below
+#include "mozilla/MemoryReporting.h"
+#include <stdint.h>
+#include "nscore.h"
+#include "nsHashKeys.h"
+#include "nsTArray.h"
+#include "nsTHashtable.h"
+
+class nsWindowSizes;
+
+template <size_t ArenaSize, typename ObjectId, size_t ObjectIdCount>
+class nsPresArena {
+ public:
+  nsPresArena() = default;
+  ~nsPresArena();
+
+  /**
+   * Pool allocation with recycler lists indexed by object-type ID (see above).
+   * Every aID must always be used with the same object size, aSize.
+   */
+  void* Allocate(ObjectId aCode, size_t aSize);
+  void Free(ObjectId aCode, void* aPtr);
+
+  enum class ArenaKind { PresShell, DisplayList };
+  /**
+   * Increment nsWindowSizes with sizes of interesting objects allocated in this
+   * arena, and put the general unclassified size in the relevant field
+   * depending on the arena size.
+   */
+  void AddSizeOfExcludingThis(nsWindowSizes&, ArenaKind) const;
+
+  void Check() { mPool.Check(); }
+
+ private:
+  class FreeList {
+   public:
+    nsTArray<void*> mEntries;
+    size_t mEntrySize;
+    size_t mEntriesEverAllocated;
+
+    FreeList() : mEntrySize(0), mEntriesEverAllocated(0) {}
+
+    size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const {
+      return mEntries.ShallowSizeOfExcludingThis(aMallocSizeOf);
+    }
+  };
+
+  FreeList mFreeLists[ObjectIdCount];
+  mozilla::ArenaAllocator<ArenaSize, 8> mPool;
+};
+
+#endif