Add unique_value_ptr.

tdutils/CMakeLists.txt

@@ -292,6 +292,7 @@ set(TDUTILS_SOURCE
   td/utils/uint128.h
   td/utils/unicode.h
   td/utils/unique_ptr.h
+  td/utils/unique_value_ptr.h
   td/utils/utf8.h
   td/utils/Variant.h
   td/utils/VectorQueue.h

tdutils/td/utils/unique_value_ptr.h

@@ -0,0 +1,93 @@
+//
+// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2023
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+#pragma once
+
+#include "td/utils/unique_ptr.h"
+
+#include <cstddef>
+#include <utility>
+
+namespace td {
+
+// copyable by value td::unique_ptr
+template <class T>
+class unique_value_ptr final {
+ public:
+  unique_value_ptr() noexcept = default;
+  unique_value_ptr(const unique_value_ptr &other) {
+    if (other != nullptr) {
+      ptr_ = make_unique<T>(*other);
+    }
+  }
+  unique_value_ptr &operator=(const unique_value_ptr &other) {
+    if (other == nullptr) {
+      ptr_ = nullptr;
+    } else {
+      ptr_ = make_unique<T>(*other);
+    }
+    return *this;
+  }
+  unique_value_ptr(unique_value_ptr &&other) noexcept = default;
+  unique_value_ptr &operator=(unique_value_ptr &&other) = default;
+  unique_value_ptr(std::nullptr_t) noexcept {
+  }
+  unique_value_ptr(unique_ptr<T> &&ptr) noexcept : ptr_(std::move(ptr)) {
+  }
+  T *get() noexcept {
+    return ptr_.get();
+  }
+  const T *get() const noexcept {
+    return ptr_.get();
+  }
+  T *operator->() noexcept {
+    return ptr_.get();
+  }
+  const T *operator->() const noexcept {
+    return ptr_.get();
+  }
+  T &operator*() noexcept {
+    return *ptr_;
+  }
+  const T &operator*() const noexcept {
+    return *ptr_;
+  }
+  explicit operator bool() const noexcept {
+    return ptr_ != nullptr;
+  }
+
+ private:
+  unique_ptr<T> ptr_;
+};
+
+template <class T>
+bool operator==(const unique_value_ptr<T> &p, std::nullptr_t) {
+  return !p;
+}
+template <class T>
+bool operator!=(const unique_value_ptr<T> &p, std::nullptr_t) {
+  return static_cast<bool>(p);
+}
+
+template <class T>
+bool operator==(const unique_value_ptr<T> &lhs, const unique_value_ptr<T> &rhs) {
+  if (lhs == nullptr) {
+    return rhs == nullptr;
+  }
+  return rhs != nullptr && *lhs == *rhs;
+}
+
+template <class T>
+bool operator!=(const unique_value_ptr<T> &lhs, const unique_value_ptr<T> &rhs) {
+  return !(lhs == rhs);
+}
+
+template <class Type, class... Args>
+unique_value_ptr<Type> make_unique_value(Args &&...args) {
+  return unique_value_ptr<Type>(make_unique<Type>(std::forward<Args>(args)...));
+}
+
+}  // namespace td

tdutils/test/misc.cpp

@@ -40,6 +40,7 @@
 #include "td/utils/translit.h"
 #include "td/utils/uint128.h"
 #include "td/utils/unicode.h"
+#include "td/utils/unique_value_ptr.h"
 #include "td/utils/utf8.h"
 
 #include <algorithm>
@@ -1260,3 +1261,32 @@ TEST(FloodControl, Fast) {
     LOG(INFO) << ++count << ": " << now;
   }
 }
+
+TEST(UniqueValuePtr, Basic) {
+  auto a = td::make_unique_value<int>(5);
+  td::unique_value_ptr<int> b;
+  ASSERT_TRUE(b == nullptr);
+  ASSERT_TRUE(a != nullptr);
+  ASSERT_TRUE(a != b);
+  b = a;
+  ASSERT_TRUE(a != nullptr);
+  ASSERT_TRUE(b != nullptr);
+  ASSERT_TRUE(a == b);
+  *a = 6;
+  ASSERT_TRUE(a != nullptr);
+  ASSERT_TRUE(b != nullptr);
+  ASSERT_TRUE(a != b);
+  b = std::move(a);
+  ASSERT_TRUE(a == nullptr);
+  ASSERT_TRUE(b != nullptr);
+  ASSERT_TRUE(a != b);
+  auto c = td::make_unique_value<td::unique_value_ptr<int>>(a);
+  ASSERT_TRUE(*c == a);
+  ASSERT_TRUE(*c == nullptr);
+  c = td::make_unique_value<td::unique_value_ptr<int>>(b);
+  ASSERT_TRUE(*c == b);
+  ASSERT_TRUE(**c == 6);
+  auto d = c;
+  ASSERT_TRUE(c == d);
+  ASSERT_TRUE(6 == **d);
+}