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tdutils/td/utils/Enumerator.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/common.h"
+#include "td/utils/misc.h"
+
+#include <map>
+#include <tuple>
+
+namespace td {
+
+template <class ValueT>
+class Enumerator {
+ public:
+  using Key = int32;
+
+  Key add(ValueT v) {
+    int32 next_id = narrow_cast<int32>(arr_.size() + 1);
+    bool was_inserted;
+    decltype(map_.begin()) it;
+    std::tie(it, was_inserted) = map_.emplace(std::move(v), next_id);
+    if (was_inserted) {
+      arr_.push_back(&it->first);
+    }
+    return it->second;
+  }
+
+  const ValueT &get(Key key) const {
+    auto pos = static_cast<size_t>(key - 1);
+    CHECK(pos < arr_.size());
+    return *arr_[pos];
+  }
+
+ private:
+  std::map<ValueT, int32> map_;
+  std::vector<const ValueT *> arr_;
+};
+
+}  // namespace td