libc/src/__support/CPP/functional.h

   1 //===-- Self contained functional header ------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC___SUPPORT_CPP_FUNCTIONAL_H
  10 #define LLVM_LIBC_SRC___SUPPORT_CPP_FUNCTIONAL_H
  11
  12 #include "src/__support/CPP/type_traits/enable_if.h"
  13 #include "src/__support/CPP/type_traits/is_convertible.h"
  14 #include "src/__support/CPP/type_traits/is_same.h"
  15 #include "src/__support/CPP/type_traits/is_void.h"
  16 #include "src/__support/CPP/type_traits/remove_cvref.h"
  17 #include "src/__support/CPP/type_traits/remove_reference.h"
  18 #include "src/__support/CPP/utility/forward.h"
  19 #include "src/__support/macros/attributes.h"
  20 #include "src/__support/macros/config.h"
  21
  22 #include <stdint.h>
  23
  24 namespace LIBC_NAMESPACE_DECL {
  25 namespace cpp {
  26
  27 /// A function type adapted from LLVM's function_ref.
  28 /// This class does not own the callable, so it is not in general safe to
  29 /// store a function.
  30 template <typename Fn> class function;
  31
  32 template <typename Ret, typename... Params> class function<Ret(Params...)> {
  33   Ret (*callback)(intptr_t callable, Params... params) = nullptr;
  34   intptr_t callable;
  35
  36   template <typename Callable>
  37   LIBC_INLINE static Ret callback_fn(intptr_t callable, Params... params) {
  38     return (*reinterpret_cast<Callable *>(callable))(
  39         cpp::forward<Params>(params)...);
  40   }
  41
  42 public:
  43   LIBC_INLINE function() = default;
  44   LIBC_INLINE function(decltype(nullptr)) {}
  45   LIBC_INLINE ~function() = default;
  46
  47   template <typename Callable>
  48   LIBC_INLINE function(
  49       Callable &&callable,
  50       // This is not the copy-constructor.
  51       enable_if_t<!cpp::is_same_v<remove_cvref_t<Callable>, function>> * =
  52           nullptr,
  53       // Functor must be callable and return a suitable type.
  54       enable_if_t<cpp::is_void_v<Ret> ||
  55                   cpp::is_convertible_v<
  56                       decltype(declval<Callable>()(declval<Params>()...)), Ret>>
  57           * = nullptr)
  58       : callback(callback_fn<cpp::remove_reference_t<Callable>>),
  59         callable(reinterpret_cast<intptr_t>(&callable)) {}
  60
  61   LIBC_INLINE Ret operator()(Params... params) const {
  62     return callback(callable, cpp::forward<Params>(params)...);
  63   }
  64
  65   LIBC_INLINE explicit operator bool() const { return callback; }
  66 };
  67
  68 } // namespace cpp
  69 } // namespace LIBC_NAMESPACE_DECL
  70
  71 #endif // LLVM_LIBC_SRC___SUPPORT_CPP_FUNCTIONAL_H