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+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_ZUCCHINI_TARGET_POOL_H_
+#define COMPONENTS_ZUCCHINI_TARGET_POOL_H_
+
+#include <stddef.h>
+
+#include <vector>
+
+#include "components/zucchini/image_utils.h"
+#include "components/zucchini/patch_reader.h"
+
+namespace zucchini {
+
+class OffsetMapper;
+class TargetSource;
+
+// Ordered container of distinct targets that have the same semantics, along
+// with a list of associated reference types, only used during patch generation.
+class TargetPool {
+ public:
+  using const_iterator = std::vector<offset_t>::const_iterator;
+
+  TargetPool();
+  // Initializes the object with given sorted and unique |targets|.
+  explicit TargetPool(std::vector<offset_t>&& targets);
+  TargetPool(TargetPool&&);
+  TargetPool(const TargetPool&);
+  ~TargetPool();
+
+  // Insert new targets from various sources. These invalidate all previous key
+  // lookups.
+  // - From a list of targets, useful for adding extra targets in Zucchini-gen:
+  void InsertTargets(const std::vector<offset_t>& targets);
+  // - From TargetSource, useful for adding extra targets in Zucchini-apply:
+  void InsertTargets(TargetSource* targets);
+  // - From list of References, useful for listing targets in Zucchini-gen:
+  void InsertTargets(const std::vector<Reference>& references);
+  // - From ReferenceReader, useful for listing targets in Zucchini-apply:
+  void InsertTargets(ReferenceReader&& references);
+
+  // Adds |type| as a reference type associated with the pool of targets.
+  void AddType(TypeTag type) { types_.push_back(type); }
+
+  // Returns a canonical key associated with a valid target at |offset|.
+  key_t KeyForOffset(offset_t offset) const;
+
+  // Returns a canonical key associated with the target nearest to |offset|.
+  key_t KeyForNearestOffset(offset_t offset) const;
+
+  // Returns the target for a |key|, which is assumed to be valid and held by
+  // this class.
+  offset_t OffsetForKey(key_t key) const { return targets_[key]; }
+
+  // Uses |offset_mapper| to transform "old" |targets_| to "new" |targets_|,
+  // resulting in sorted and unique targets.
+  void FilterAndProject(const OffsetMapper& offset_mapper);
+
+  // Accessors for testing.
+  const std::vector<offset_t>& targets() const { return targets_; }
+  const std::vector<TypeTag>& types() const { return types_; }
+
+  // Returns the number of targets.
+  size_t size() const { return targets_.size(); }
+  const_iterator begin() const { return targets_.cbegin(); }
+  const_iterator end() const { return targets_.cend(); }
+
+ private:
+  std::vector<TypeTag> types_;     // Enumerates type_tag for this pool.
+  std::vector<offset_t> targets_;  // Targets for pool in ascending order.
+};
+
+}  // namespace zucchini
+
+#endif  // COMPONENTS_ZUCCHINI_TARGET_POOL_H_