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diff --git a/runtime/gc/accounting/card_table.h b/runtime/gc/accounting/card_table.h
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+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_SRC_GC_CARDTABLE_H_
+#define ART_SRC_GC_CARDTABLE_H_
+
+#include "globals.h"
+#include "locks.h"
+#include "mem_map.h"
+#include "UniquePtr.h"
+
+namespace art {
+
+namespace mirror {
+  class Object;
+}  // namespace mirror
+
+namespace gc {
+
+namespace space {
+  class ContinuousSpace;
+}  // namespace space
+
+class Heap;
+
+namespace accounting {
+
+class SpaceBitmap;
+
+// Maintain a card table from the the write barrier. All writes of
+// non-NULL values to heap addresses should go through an entry in
+// WriteBarrier, and from there to here.
+class CardTable {
+ public:
+  static const size_t kCardShift = 7;
+  static const size_t kCardSize = (1 << kCardShift);
+  static const uint8_t kCardClean  = 0x0;
+  static const uint8_t kCardDirty = 0x70;
+
+  static CardTable* Create(const byte* heap_begin, size_t heap_capacity);
+
+  // Set the card associated with the given address to GC_CARD_DIRTY.
+  void MarkCard(const void *addr) {
+    byte* card_addr = CardFromAddr(addr);
+    *card_addr = kCardDirty;
+  }
+
+  // Is the object on a dirty card?
+  bool IsDirty(const mirror::Object* obj) const {
+    return GetCard(obj) == kCardDirty;
+  }
+
+  // Return the state of the card at an address.
+  byte GetCard(const mirror::Object* obj) const {
+    return *CardFromAddr(obj);
+  }
+
+  // Visit and clear cards within memory range, only visits dirty cards.
+  template <typename Visitor>
+  void VisitClear(const void* start, const void* end, const Visitor& visitor) {
+    byte* card_start = CardFromAddr(start);
+    byte* card_end = CardFromAddr(end);
+    for (byte* it = card_start; it != card_end; ++it) {
+      if (*it == kCardDirty) {
+        *it = kCardClean;
+        visitor(it);
+      }
+    }
+  }
+
+  // Returns a value that when added to a heap address >> GC_CARD_SHIFT will address the appropriate
+  // card table byte. For convenience this value is cached in every Thread
+  byte* GetBiasedBegin() const {
+    return biased_begin_;
+  }
+
+  /*
+   * Visitor is expected to take in a card and return the new value. When a value is modified, the
+   * modify visitor is called.
+   * visitor: The visitor which modifies the cards. Returns the new value for a card given an old
+   * value.
+   * modified: Whenever the visitor modifies a card, this visitor is called on the card. Enables
+   * us to know which cards got cleared.
+   */
+  template <typename Visitor, typename ModifiedVisitor>
+  void ModifyCardsAtomic(byte* scan_begin, byte* scan_end, const Visitor& visitor,
+                         const ModifiedVisitor& modified);
+
+  // For every dirty at least minumum age between begin and end invoke the visitor with the
+  // specified argument.
+  template <typename Visitor, typename FingerVisitor>
+  void Scan(SpaceBitmap* bitmap, byte* scan_begin, byte* scan_end,
+            const Visitor& visitor, const FingerVisitor& finger_visitor,
+            const byte minimum_age = kCardDirty) const
+      EXCLUSIVE_LOCKS_REQUIRED(Locks::heap_bitmap_lock_)
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+
+  // Assertion used to check the given address is covered by the card table
+  void CheckAddrIsInCardTable(const byte* addr) const;
+
+  // Resets all of the bytes in the card table to clean.
+  void ClearCardTable();
+
+  // Resets all of the bytes in the card table which do not map to the image space.
+  void ClearSpaceCards(space::ContinuousSpace* space);
+
+  // Returns the first address in the heap which maps to this card.
+  void* AddrFromCard(const byte *card_addr) const;
+
+  // Returns the address of the relevant byte in the card table, given an address on the heap.
+  byte* CardFromAddr(const void *addr) const;
+
+  bool AddrIsInCardTable(const void* addr) const;
+
+ private:
+  CardTable(MemMap* begin, byte* biased_begin, size_t offset);
+
+  // Returns true iff the card table address is within the bounds of the card table.
+  bool IsValidCard(const byte* card_addr) const {
+    byte* begin = mem_map_->Begin() + offset_;
+    byte* end = mem_map_->End();
+    return card_addr >= begin && card_addr < end;
+  }
+
+  void CheckCardValid(byte* card) const;
+
+  // Verifies that all gray objects are on a dirty card.
+  void VerifyCardTable();
+
+  // Mmapped pages for the card table
+  UniquePtr<MemMap> mem_map_;
+  // Value used to compute card table addresses from object addresses, see GetBiasedBegin
+  byte* const biased_begin_;
+  // Card table doesn't begin at the beginning of the mem_map_, instead it is displaced by offset
+  // to allow the byte value of biased_begin_ to equal GC_CARD_DIRTY
+  const size_t offset_;
+};
+
+}  // namespace accounting
+}  // namespace gc
+}  // namespace art
+
+#endif  // ART_SRC_GC_CARDTABLE_H_