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tdutils/td/utils/VectorQueue.h

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+/*
+    This file is part of TON Blockchain Library.
+
+    TON Blockchain Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 2 of the License, or
+    (at your option) any later version.
+
+    TON Blockchain Library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with TON Blockchain Library.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2017-2019 Telegram Systems LLP
+*/
+#pragma once
+
+#include "td/utils/Span.h"
+
+#include <utility>
+#include <vector>
+
+namespace td {
+
+template <class T>
+class VectorQueue {
+ public:
+  template <class S>
+  void push(S &&s) {
+    vector_.push_back(std::forward<S>(s));
+  }
+  template <class... Args>
+  void emplace(Args &&... args) {
+    vector_.emplace_back(std::forward<Args>(args)...);
+  }
+  T pop() {
+    try_shrink();
+    return std::move(vector_[read_pos_++]);
+  }
+  void pop_n(size_t n) {
+    read_pos_ += n;
+    try_shrink();
+  }
+  T &front() {
+    return vector_[read_pos_];
+  }
+  T &back() {
+    return vector_.back();
+  }
+  bool empty() const {
+    return size() == 0;
+  }
+  size_t size() const {
+    return vector_.size() - read_pos_;
+  }
+  T *data() {
+    return vector_.data() + read_pos_;
+  }
+  const T *data() const {
+    return vector_.data() + read_pos_;
+  }
+  Span<T> as_span() const {
+    return {data(), size()};
+  }
+  MutableSpan<T> as_mutable_span() {
+    return {data(), size()};
+  }
+
+ private:
+  std::vector<T> vector_;
+  size_t read_pos_{0};
+
+  void try_shrink() {
+    if (read_pos_ * 2 > vector_.size() && read_pos_ > 4) {
+      vector_.erase(vector_.begin(), vector_.begin() + read_pos_);
+      read_pos_ = 0;
+    }
+  }
+};
+
+}  // namespace td