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diff --git a/libdexfile/dex/dex_file_layout.h b/libdexfile/dex/dex_file_layout.h
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+++ b/libdexfile/dex/dex_file_layout.h
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+/*
+ * Copyright (C) 2017 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_LIBDEXFILE_DEX_DEX_FILE_LAYOUT_H_
+#define ART_LIBDEXFILE_DEX_DEX_FILE_LAYOUT_H_
+
+#include <algorithm>
+#include <cstdint>
+#include <iosfwd>
+
+#include <android-base/logging.h>
+
+namespace art {
+
+class DexFile;
+
+enum class LayoutType : uint8_t {
+  // Layout of things that are hot (commonly accessed), these should be pinned or madvised will
+  // need.
+  kLayoutTypeHot,
+  // Layout of things that are randomly used. These should be advised to random access.
+  // Without layout, this is the default mode when loading a dex file.
+  kLayoutTypeSometimesUsed,
+  // Layout of things that are only used during startup, these can be madvised after launch.
+  kLayoutTypeStartupOnly,
+  // Layout of things that are needed probably only once (class initializers). These can be
+  // madvised during trim events.
+  kLayoutTypeUsedOnce,
+  // Layout of things that are thought to be unused. These things should be advised to random
+  // access.
+  kLayoutTypeUnused,
+  // Unused value, just the number of elements in the enum.
+  kLayoutTypeCount,
+};
+std::ostream& operator<<(std::ostream& os, const LayoutType& collector_type);
+
+// Return the "best" layout option if the same item has multiple different layouts.
+static inline LayoutType MergeLayoutType(LayoutType a, LayoutType b) {
+  return std::min(a, b);
+}
+
+enum class MadviseState : uint8_t {
+  // Madvise based on a file that was just loaded.
+  kMadviseStateAtLoad,
+  // Madvise based after launch is finished.
+  kMadviseStateFinishedLaunch,
+  // Trim by madvising code that is unlikely to be too important in the future.
+  kMadviseStateFinishedTrim,
+};
+std::ostream& operator<<(std::ostream& os, const MadviseState& collector_type);
+
+// A dex layout section such as code items or strings. Each section is composed of subsections
+// that are laid out adjacently to each other such as (hot, unused, startup, etc...).
+class DexLayoutSection {
+ public:
+  // A subsection is a a continuous range of dex file that is all part of the same layout hint.
+  class Subsection {
+   public:
+    // Use uint32_t to handle 32/64 bit cross compilation.
+    uint32_t start_offset_ = 0u;
+    uint32_t end_offset_ = 0u;
+
+    bool Contains(uint32_t offset) const {
+      return start_offset_ <= offset && offset < end_offset_;
+    }
+
+    bool Size() const {
+      DCHECK_LE(start_offset_, end_offset_);
+      return end_offset_ - start_offset_;
+    }
+
+    void CombineSection(uint32_t start_offset, uint32_t end_offset) {
+      DCHECK_LE(start_offset, end_offset);
+      if (start_offset_ == end_offset_) {
+        start_offset_ = start_offset;
+        end_offset_ = end_offset;
+      } else  {
+        start_offset_ = std::min(start_offset_, start_offset);
+        end_offset_ = std::max(end_offset_, end_offset);
+      }
+    }
+
+    void Madvise(const DexFile* dex_file, int advice) const;
+  };
+
+  // Madvise the largest page-aligned region contained in [begin, end).
+  static int MadviseLargestPageAlignedRegion(const uint8_t* begin, const uint8_t* end, int advice);
+
+  Subsection parts_[static_cast<size_t>(LayoutType::kLayoutTypeCount)];
+};
+
+// A set of dex layout sections, currently there is only one section for code and one for strings.
+class DexLayoutSections {
+ public:
+  enum class SectionType : uint8_t {
+    kSectionTypeCode,
+    kSectionTypeStrings,
+    kSectionCount,
+  };
+
+  // Advise access about the dex file based on layout. The caller is expected to have already
+  // madvised to MADV_RANDOM.
+  void Madvise(const DexFile* dex_file, MadviseState state) const;
+
+  DexLayoutSection sections_[static_cast<size_t>(SectionType::kSectionCount)];
+};
+
+std::ostream& operator<<(std::ostream& os, const DexLayoutSections::SectionType& collector_type);
+std::ostream& operator<<(std::ostream& os, const DexLayoutSection& section);
+std::ostream& operator<<(std::ostream& os, const DexLayoutSections& sections);
+
+}  // namespace art
+
+#endif  // ART_LIBDEXFILE_DEX_DEX_FILE_LAYOUT_H_