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Commit 6392d6a7 authored by Dominik Laskowski's avatar Dominik Laskowski Committed by Automerger Merge Worker
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Merge "FTL: Add Optional<T>::or_else" into udc-dev am: 44c11c9f 

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/native/+/21802733



Change-Id: I44a426a85d37e7006b658026579eda15cae26645
Signed-off-by: default avatarAutomerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
parents 6d7fb493 44c11c9f

include/ftl/details/optional.h

+10 −0
Original line number Diff line number Diff line
@@ -54,5 +54,15 @@ struct and_then_result { 
template <typename F, typename T>

using and_then_result_t = typename and_then_result<F, T>::type;



template <typename F, typename T>

struct or_else_result {

  using type = remove_cvref_t<std::invoke_result_t<F>>;

  static_assert(std::is_same_v<type, std::optional<T>> || std::is_same_v<type, Optional<T>>,

                "or_else function must return an optional T");

};



template <typename F, typename T>

using or_else_result_t = typename or_else_result<F, T>::type;



}  // namespace details

}  // namespace android::ftl

include/ftl/optional.h

+13 −1
Original line number Diff line number Diff line
@@ -96,13 +96,25 @@ struct Optional final : std::optional<T> { 
    return R();

  }



  // Returns this Optional<T> if not nullopt, or else the Optional<T> returned by the function F.

  template <typename F>

  constexpr auto or_else(F&& f) const& -> details::or_else_result_t<F, T> {

    if (has_value()) return *this;

    return std::forward<F>(f)();

  }



  template <typename F>

  constexpr auto or_else(F&& f) && -> details::or_else_result_t<F, T> {

    if (has_value()) return std::move(*this);

    return std::forward<F>(f)();

  }



  // Delete new for this class. Its base doesn't have a virtual destructor, and

  // if it got deleted via base class pointer, it would cause undefined

  // behavior. There's not a good reason to allocate this object on the heap

  // anyway.

  static void* operator new(size_t) = delete;

  static void* operator new[](size_t) = delete;



};



template <typename T, typename U>

libs/ftl/optional_test.cpp

+40 −0
Original line number Diff line number Diff line
@@ -164,6 +164,46 @@ TEST(Optional, AndThen) { 
                     }));

}



TEST(Optional, OrElse) {

  // Non-empty.

  {

    const Optional opt = false;

    EXPECT_EQ(false, opt.or_else([] { return Optional(true); }));

    EXPECT_EQ('x', Optional('x').or_else([] { return std::make_optional('y'); }));

  }



  // Empty.

  {

    const Optional<int> opt;

    EXPECT_EQ(123, opt.or_else([]() -> Optional<int> { return 123; }));

    EXPECT_EQ("abc"s, Optional<std::string>().or_else([] { return Optional("abc"s); }));

  }

  {

    bool empty = false;

    EXPECT_EQ(Optional<float>(), Optional<float>().or_else([&empty]() -> Optional<float> {

      empty = true;

      return std::nullopt;

    }));

    EXPECT_TRUE(empty);

  }



  // Chaining.

  using StringVector = StaticVector<std::string, 3>;

  EXPECT_EQ(999, Optional(StaticVector{"1"s, "0"s, "0"s})

                     .and_then([](StringVector&& v) -> Optional<StringVector> {

                       if (v.push_back("0"s)) return v;

                       return {};

                     })

                     .or_else([] {

                       return Optional(StaticVector{"9"s, "9"s, "9"s});

                     })

                     .transform([](const StringVector& v) {

                       return std::accumulate(v.begin(), v.end(), std::string());

                     })

                     .and_then(parse_int)

                     .or_else([] { return Optional(-1); }));

}



// Comparison.

namespace {