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| 1 | // -*- C++ -*- |
|---|---|
| 2 | //===----------------------------------------------------------------------===// |
| 3 | // |
| 4 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 5 | // See https://llvm.org/LICENSE.txt for license information. |
| 6 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 7 | // |
| 8 | //===----------------------------------------------------------------------===// |
| 9 | |
| 10 | #ifndef _LIBCPP___FLAT_MAP_UTILS_H |
| 11 | #define _LIBCPP___FLAT_MAP_UTILS_H |
| 12 | |
| 13 | #include <__config> |
| 14 | #include <__type_traits/container_traits.h> |
| 15 | #include <__utility/exception_guard.h> |
| 16 | #include <__utility/forward.h> |
| 17 | #include <__utility/move.h> |
| 18 | |
| 19 | #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) |
| 20 | # pragma GCC system_header |
| 21 | #endif |
| 22 | |
| 23 | _LIBCPP_PUSH_MACROS |
| 24 | #include <__undef_macros> |
| 25 | |
| 26 | #if _LIBCPP_STD_VER >= 23 |
| 27 | |
| 28 | _LIBCPP_BEGIN_NAMESPACE_STD |
| 29 | |
| 30 | // These utilities are defined in a class instead of a namespace so that this class can be befriended more easily. |
| 31 | struct __flat_map_utils { |
| 32 | // Emplace a {key: value} into a flat_{multi}map, at the exact position that |
| 33 | // __it_key and __it_mapped point to, assuming that the key is not already present in the map. |
| 34 | // When an exception is thrown during the emplacement, the function will try its best to |
| 35 | // roll back the changes it made to the map. If it cannot roll back the changes, it will |
| 36 | // clear the map. |
| 37 | template <class _Map, class _IterK, class _IterM, class _KeyArg, class... _MArgs> |
| 38 | _LIBCPP_HIDE_FROM_ABI static typename _Map::iterator __emplace_exact_pos( |
| 39 | _Map& __map, _IterK&& __it_key, _IterM&& __it_mapped, _KeyArg&& __key, _MArgs&&... __mapped_args) { |
| 40 | auto __on_key_failed = std::__make_exception_guard([&]() noexcept { |
| 41 | using _KeyContainer = typename _Map::key_container_type; |
| 42 | if constexpr (__container_traits<_KeyContainer>::__emplacement_has_strong_exception_safety_guarantee) { |
| 43 | // Nothing to roll back! |
| 44 | } else { |
| 45 | // we need to clear both because we don't know the state of our keys anymore |
| 46 | __map.clear() /* noexcept */; |
| 47 | } |
| 48 | }); |
| 49 | auto __key_it = __map.__containers_.keys.emplace(__it_key, std::forward<_KeyArg>(__key)); |
| 50 | __on_key_failed.__complete(); |
| 51 | |
| 52 | auto __on_value_failed = std::__make_exception_guard([&]() noexcept { |
| 53 | using _MappedContainer = typename _Map::mapped_container_type; |
| 54 | if constexpr (!__container_traits<_MappedContainer>::__emplacement_has_strong_exception_safety_guarantee) { |
| 55 | // we need to clear both because we don't know the state of our values anymore |
| 56 | __map.clear() /* noexcept */; |
| 57 | } else { |
| 58 | // In this case, we know the values are just like before we attempted emplacement, |
| 59 | // and we also know that the keys have been emplaced successfully. Just roll back the keys. |
| 60 | # if _LIBCPP_HAS_EXCEPTIONS |
| 61 | try { |
| 62 | # endif // _LIBCPP_HAS_EXCEPTIONS |
| 63 | __map.__containers_.keys.erase(__key_it); |
| 64 | # if _LIBCPP_HAS_EXCEPTIONS |
| 65 | } catch (...) { |
| 66 | // Now things are funky for real. We're failing to rollback the keys. |
| 67 | // Just give up and clear the whole thing. |
| 68 | // |
| 69 | // Also, swallow the exception that happened during the rollback and let the |
| 70 | // original value-emplacement exception propagate normally. |
| 71 | __map.clear() /* noexcept */; |
| 72 | } |
| 73 | # endif // _LIBCPP_HAS_EXCEPTIONS |
| 74 | } |
| 75 | }); |
| 76 | auto __mapped_it = __map.__containers_.values.emplace(__it_mapped, std::forward<_MArgs>(__mapped_args)...); |
| 77 | __on_value_failed.__complete(); |
| 78 | |
| 79 | return typename _Map::iterator(std::move(__key_it), std::move(__mapped_it)); |
| 80 | } |
| 81 | |
| 82 | // TODO: We could optimize this, see |
| 83 | // https://github.com/llvm/llvm-project/issues/108624 |
| 84 | template <class _Map, class _InputIterator, class _Sentinel> |
| 85 | _LIBCPP_HIDE_FROM_ABI static typename _Map::size_type |
| 86 | __append(_Map& __map, _InputIterator __first, _Sentinel __last) { |
| 87 | typename _Map::size_type __num_appended = 0; |
| 88 | for (; __first != __last; ++__first) { |
| 89 | typename _Map::value_type __kv = *__first; |
| 90 | __map.__containers_.keys.insert(__map.__containers_.keys.end(), std::move(__kv.first)); |
| 91 | __map.__containers_.values.insert(__map.__containers_.values.end(), std::move(__kv.second)); |
| 92 | ++__num_appended; |
| 93 | } |
| 94 | return __num_appended; |
| 95 | } |
| 96 | }; |
| 97 | _LIBCPP_END_NAMESPACE_STD |
| 98 | |
| 99 | #endif // _LIBCPP_STD_VER >= 23 |
| 100 | |
| 101 | _LIBCPP_POP_MACROS |
| 102 | |
| 103 | #endif // #define _LIBCPP___FLAT_MAP_UTILS_H |
| 104 |
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