diff options
| -rw-r--r-- | indra/llcommon/CMakeLists.txt | 2 | ||||
| -rw-r--r-- | indra/llcommon/tests/tuple_test.cpp | 47 | ||||
| -rw-r--r-- | indra/llcommon/tuple.h | 84 |
3 files changed, 133 insertions, 0 deletions
diff --git a/indra/llcommon/CMakeLists.txt b/indra/llcommon/CMakeLists.txt index dd266630ea..6558219462 100644 --- a/indra/llcommon/CMakeLists.txt +++ b/indra/llcommon/CMakeLists.txt @@ -254,6 +254,7 @@ set(llcommon_HEADER_FILES stdtypes.h stringize.h timer.h + tuple.h u64.h StackWalker.h ) @@ -358,6 +359,7 @@ if (LL_TESTS) LL_ADD_INTEGRATION_TEST(lluri "" "${test_libs}") LL_ADD_INTEGRATION_TEST(llunits "" "${test_libs}") LL_ADD_INTEGRATION_TEST(stringize "" "${test_libs}") + LL_ADD_INTEGRATION_TEST(tuple "" "${test_libs}") ## llexception_test.cpp isn't a regression test, and doesn't need to be run ## every build. It's to help a developer make implementation choices about diff --git a/indra/llcommon/tests/tuple_test.cpp b/indra/llcommon/tests/tuple_test.cpp new file mode 100644 index 0000000000..af94e2086c --- /dev/null +++ b/indra/llcommon/tests/tuple_test.cpp @@ -0,0 +1,47 @@ +/** + * @file tuple_test.cpp + * @author Nat Goodspeed + * @date 2021-10-04 + * @brief Test for tuple. + * + * $LicenseInfo:firstyear=2021&license=viewerlgpl$ + * Copyright (c) 2021, Linden Research, Inc. + * $/LicenseInfo$ + */ + +// Precompiled header +#include "linden_common.h" +// associated header +#include "tuple.h" +// STL headers +// std headers +// external library headers +// other Linden headers +#include "../test/lltut.h" + +/***************************************************************************** +* TUT +*****************************************************************************/ +namespace tut +{ + struct tuple_data + { + }; + typedef test_group<tuple_data> tuple_group; + typedef tuple_group::object object; + tuple_group tuplegrp("tuple"); + + template<> template<> + void object::test<1>() + { + set_test_name("tuple"); + std::tuple<std::string, int> tup{ "abc", 17 }; + std::tuple<int, std::string, int> ptup{ tuple_cons(34, tup) }; + std::tuple<std::string, int> tup2; + int i; + std::tie(i, tup2) = tuple_split(ptup); + ensure_equals("tuple_car() fail", i, 34); + ensure_equals("tuple_cdr() (0) fail", std::get<0>(tup2), "abc"); + ensure_equals("tuple_cdr() (1) fail", std::get<1>(tup2), 17); + } +} // namespace tut diff --git a/indra/llcommon/tuple.h b/indra/llcommon/tuple.h new file mode 100644 index 0000000000..bfe7e3c2ba --- /dev/null +++ b/indra/llcommon/tuple.h @@ -0,0 +1,84 @@ +/** + * @file tuple.h + * @author Nat Goodspeed + * @date 2021-10-04 + * @brief A couple tuple utilities + * + * $LicenseInfo:firstyear=2021&license=viewerlgpl$ + * Copyright (c) 2021, Linden Research, Inc. + * $/LicenseInfo$ + */ + +#if ! defined(LL_TUPLE_H) +#define LL_TUPLE_H + +#include <tuple> +#include <type_traits> // std::remove_reference +#include <utility> // std::pair + +/** + * tuple_cons() behaves like LISP cons: it uses std::tuple_cat() to prepend a + * new item of arbitrary type to an existing std::tuple. + */ +template <typename First, typename... Rest, typename Tuple_=std::tuple<Rest...>> +auto tuple_cons(First&& first, Tuple_&& rest) +{ + // All we need to do is make a tuple containing 'first', and let + // tuple_cat() do the hard part. + return std::tuple_cat(std::tuple<First>(std::forward<First>(first)), + std::forward<Tuple_>(rest)); +} + +/** + * tuple_car() behaves like LISP car: it extracts the first item from a + * std::tuple. + */ +template <typename... Args, typename Tuple_=std::tuple<Args...>> +auto tuple_car(Tuple_&& tuple) +{ + return std::get<0>(std::forward<Tuple_>(tuple)); +} + +/** + * tuple_cdr() behaves like LISP cdr: it returns a new tuple containing + * everything BUT the first item. + */ +// derived from https://stackoverflow.com/a/24046437 +template <typename Tuple, std::size_t... Indices> +auto tuple_cdr_(Tuple&& tuple, const std::index_sequence<Indices...>) +{ + // Given an index sequence from [0..N-1), extract tuple items [1..N) + return std::make_tuple(std::get<Indices+1u>(std::forward<Tuple>(tuple))...); +} + +template <typename Tuple> +auto tuple_cdr(Tuple&& tuple) +{ + return tuple_cdr_( + std::forward<Tuple>(tuple), + // Pass helper function an index sequence one item shorter than tuple + std::make_index_sequence< + std::tuple_size< + // tuple_size doesn't like reference types + typename std::remove_reference<Tuple>::type + >::value - 1u> + ()); +} + +/** + * tuple_split(), the opposite of tuple_cons(), has no direct analog in LISP. + * It returns a std::pair of tuple_car(), tuple_cdr(). We could call this + * function tuple_car_cdr(), or tuple_slice() or some such. But tuple_split() + * feels more descriptive. + */ +template <typename... Args, typename Tuple_=std::tuple<Args...>> +auto tuple_split(Tuple_&& tuple) +{ + // We're not really worried about forwarding multiple times a tuple that + // might contain move-only items, because the implementation above only + // applies std::get() exactly once to each item. + return std::make_pair(tuple_car(std::forward<Tuple_>(tuple)), + tuple_cdr(std::forward<Tuple_>(tuple))); +} + +#endif /* ! defined(LL_TUPLE_H) */ |