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diff --git a/runtime/gc/space/space.h b/runtime/gc/space/space.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_SPACE_SPACE_H_
+#define ART_SRC_GC_SPACE_SPACE_H_
+
+#include <string>
+
+#include "UniquePtr.h"
+#include "base/macros.h"
+#include "base/mutex.h"
+#include "gc/accounting/space_bitmap.h"
+#include "globals.h"
+#include "image.h"
+#include "mem_map.h"
+
+namespace art {
+namespace mirror {
+  class Object;
+}  // namespace mirror
+
+namespace gc {
+
+namespace accounting {
+  class SpaceBitmap;
+} // namespace accounting
+
+class Heap;
+
+namespace space {
+
+class DlMallocSpace;
+class ImageSpace;
+class LargeObjectSpace;
+
+static const bool kDebugSpaces = kIsDebugBuild;
+
+// See Space::GetGcRetentionPolicy.
+enum GcRetentionPolicy {
+  // Objects are retained forever with this policy for a space.
+  kGcRetentionPolicyNeverCollect,
+  // Every GC cycle will attempt to collect objects in this space.
+  kGcRetentionPolicyAlwaysCollect,
+  // Objects will be considered for collection only in "full" GC cycles, ie faster partial
+  // collections won't scan these areas such as the Zygote.
+  kGcRetentionPolicyFullCollect,
+};
+std::ostream& operator<<(std::ostream& os, const GcRetentionPolicy& policy);
+
+enum SpaceType {
+  kSpaceTypeImageSpace,
+  kSpaceTypeAllocSpace,
+  kSpaceTypeZygoteSpace,
+  kSpaceTypeLargeObjectSpace,
+};
+std::ostream& operator<<(std::ostream& os, const SpaceType& space_type);
+
+// A space contains memory allocated for managed objects.
+class Space {
+ public:
+  // Dump space. Also key method for C++ vtables.
+  virtual void Dump(std::ostream& os) const;
+
+  // Name of the space. May vary, for example before/after the Zygote fork.
+  const char* GetName() const {
+    return name_.c_str();
+  }
+
+  // The policy of when objects are collected associated with this space.
+  GcRetentionPolicy GetGcRetentionPolicy() const {
+    return gc_retention_policy_;
+  }
+
+  // Does the space support allocation?
+  virtual bool CanAllocateInto() const {
+    return true;
+  }
+
+  // Is the given object contained within this space?
+  virtual bool Contains(const mirror::Object* obj) const = 0;
+
+  // The kind of space this: image, alloc, zygote, large object.
+  virtual SpaceType GetType() const = 0;
+
+  // Is this an image space, ie one backed by a memory mapped image file.
+  bool IsImageSpace() const {
+    return GetType() == kSpaceTypeImageSpace;
+  }
+  ImageSpace* AsImageSpace();
+
+  // Is this a dlmalloc backed allocation space?
+  bool IsDlMallocSpace() const {
+    SpaceType type = GetType();
+    return type == kSpaceTypeAllocSpace || type == kSpaceTypeZygoteSpace;
+  }
+  DlMallocSpace* AsDlMallocSpace();
+
+  // Is this the space allocated into by the Zygote and no-longer in use?
+  bool IsZygoteSpace() const {
+    return GetType() == kSpaceTypeZygoteSpace;
+  }
+  DlMallocSpace* AsZygoteSpace();
+
+  // Does this space hold large objects and implement the large object space abstraction?
+  bool IsLargeObjectSpace() const {
+    return GetType() == kSpaceTypeLargeObjectSpace;
+  }
+  LargeObjectSpace* AsLargeObjectSpace();
+
+  virtual ~Space() {}
+
+ protected:
+  Space(const std::string& name, GcRetentionPolicy gc_retention_policy);
+
+  void SetGcRetentionPolicy(GcRetentionPolicy gc_retention_policy) {
+    gc_retention_policy_ = gc_retention_policy;
+  }
+
+  // Name of the space that may vary due to the Zygote fork.
+  std::string name_;
+
+ private:
+  // When should objects within this space be reclaimed? Not constant as we vary it in the case
+  // of Zygote forking.
+  GcRetentionPolicy gc_retention_policy_;
+
+  friend class art::gc::Heap;
+
+  DISALLOW_COPY_AND_ASSIGN(Space);
+};
+std::ostream& operator<<(std::ostream& os, const Space& space);
+
+// AllocSpace interface.
+class AllocSpace {
+ public:
+  // Number of bytes currently allocated.
+  virtual uint64_t GetBytesAllocated() const = 0;
+  // Number of objects currently allocated.
+  virtual uint64_t GetObjectsAllocated() const = 0;
+  // Number of bytes allocated since the space was created.
+  virtual uint64_t GetTotalBytesAllocated() const = 0;
+  // Number of objects allocated since the space was created.
+  virtual uint64_t GetTotalObjectsAllocated() const = 0;
+
+  // Allocate num_bytes without allowing growth.
+  virtual mirror::Object* Alloc(Thread* self, size_t num_bytes) = 0;
+
+  // Return the storage space required by obj.
+  virtual size_t AllocationSize(const mirror::Object* obj) = 0;
+
+  // Returns how many bytes were freed.
+  virtual size_t Free(Thread* self, mirror::Object* ptr) = 0;
+
+  // Returns how many bytes were freed.
+  virtual size_t FreeList(Thread* self, size_t num_ptrs, mirror::Object** ptrs) = 0;
+
+ protected:
+  AllocSpace() {}
+  virtual ~AllocSpace() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AllocSpace);
+};
+
+// Continuous spaces have bitmaps, and an address range. Although not required, objects within
+// continuous spaces can be marked in the card table.
+class ContinuousSpace : public Space {
+ public:
+  // Address at which the space begins
+  byte* Begin() const {
+    return begin_;
+  }
+
+  // Address at which the space ends, which may vary as the space is filled.
+  byte* End() const {
+    return end_;
+  }
+
+  // Current size of space
+  size_t Size() const {
+    return End() - Begin();
+  }
+
+  virtual accounting::SpaceBitmap* GetLiveBitmap() const = 0;
+  virtual accounting::SpaceBitmap* GetMarkBitmap() const = 0;
+
+  // Is object within this space? We check to see if the pointer is beyond the end first as
+  // continuous spaces are iterated over from low to high.
+  bool HasAddress(const mirror::Object* obj) const {
+    const byte* byte_ptr = reinterpret_cast<const byte*>(obj);
+    return byte_ptr < End() && byte_ptr >= Begin();
+  }
+
+  bool Contains(const mirror::Object* obj) const {
+    return HasAddress(obj);
+  }
+
+  virtual ~ContinuousSpace() {}
+
+ protected:
+  ContinuousSpace(const std::string& name, GcRetentionPolicy gc_retention_policy,
+                  byte* begin, byte* end) :
+      Space(name, gc_retention_policy), begin_(begin), end_(end) {
+  }
+
+
+  // The beginning of the storage for fast access.
+  byte* const begin_;
+
+  // Current end of the space.
+  byte* end_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ContinuousSpace);
+};
+
+// A space where objects may be allocated higgledy-piggledy throughout virtual memory. Currently
+// the card table can't cover these objects and so the write barrier shouldn't be triggered. This
+// is suitable for use for large primitive arrays.
+class DiscontinuousSpace : public Space {
+ public:
+  accounting::SpaceSetMap* GetLiveObjects() const {
+    return live_objects_.get();
+  }
+
+  accounting::SpaceSetMap* GetMarkObjects() const {
+    return mark_objects_.get();
+  }
+
+  virtual ~DiscontinuousSpace() {}
+
+ protected:
+  DiscontinuousSpace(const std::string& name, GcRetentionPolicy gc_retention_policy);
+
+  UniquePtr<accounting::SpaceSetMap> live_objects_;
+  UniquePtr<accounting::SpaceSetMap> mark_objects_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DiscontinuousSpace);
+};
+
+class MemMapSpace : public ContinuousSpace {
+ public:
+  // Maximum which the mapped space can grow to.
+  virtual size_t Capacity() const {
+    return mem_map_->Size();
+  }
+
+  // Size of the space without a limit on its growth. By default this is just the Capacity, but
+  // for the allocation space we support starting with a small heap and then extending it.
+  virtual size_t NonGrowthLimitCapacity() const {
+    return Capacity();
+  }
+
+ protected:
+  MemMapSpace(const std::string& name, MemMap* mem_map, size_t initial_size,
+              GcRetentionPolicy gc_retention_policy)
+      : ContinuousSpace(name, gc_retention_policy,
+                        mem_map->Begin(), mem_map->Begin() + initial_size),
+        mem_map_(mem_map) {
+  }
+
+  MemMap* GetMemMap() {
+    return mem_map_.get();
+  }
+
+  const MemMap* GetMemMap() const {
+    return mem_map_.get();
+  }
+
+ private:
+  // Underlying storage of the space
+  UniquePtr<MemMap> mem_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(MemMapSpace);
+};
+
+}  // namespace space
+}  // namespace gc
+}  // namespace art
+
+#endif  // ART_SRC_GC_SPACE_SPACE_H_