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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_
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