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diff --git a/src/base/bottom_n.h b/src/base/bottom_n.h
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+++ b/src/base/bottom_n.h
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+// Copyright 2018 Google LLC
+//
+// 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
+//
+//     https://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 ASTC_CODEC_BASE_BOTTOM_N_H_
+#define ASTC_CODEC_BASE_BOTTOM_N_H_
+
+#include <algorithm>
+#include <functional>
+#include <vector>
+
+namespace astc_codec {
+namespace base {
+
+// Used to aggregate the lowest N values of data supplied.
+template<typename T, typename CompareFn = std::less<T>>
+class BottomN {
+ public:
+  typedef std::vector<T> ContainerType;
+
+  // Creates an empty BottomN with limit |max_size|.
+  BottomN(size_t max_size) : max_size_(max_size) { }
+
+  bool Empty() const { return data_.empty(); }
+  size_t Size() const { return data_.size(); }
+
+  const T& Top() const { return data_.front(); }
+
+  void Push(const T& value) {
+    if (data_.size() < max_size_ || compare_(value, Top())) {
+      data_.push_back(value);
+      std::push_heap(data_.begin(), data_.end(), compare_);
+
+      if (Size() > max_size_) {
+        PopTop();
+      }
+    }
+  }
+
+  std::vector<T> Pop() {
+    const size_t len = Size();
+    std::vector<T> result(len);
+
+    for (size_t i = 0; i < len; ++i) {
+      result[len - i - 1] = PopTop();
+    }
+
+    return result;
+  }
+
+ private:
+  T PopTop() {
+    std::pop_heap(data_.begin(), data_.end(), compare_);
+    T result = data_.back();
+    data_.pop_back();
+    return result;
+  }
+
+  ContainerType data_;
+  CompareFn compare_;
+
+  const size_t max_size_;
+};
+
+}  // namespace base
+}  // namespace astc_codec
+
+#endif  // ASTC_CODEC_BASE_BOTTOM_N_H_