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.h"
  13 #include "src/__support/CPP/utility.h"
  14 #include "src/__support/macros/attributes.h"
  15
  16 #include <stdint.h>
  17
  18 namespace __llvm_libc {
  19 namespace cpp {
  20
  21 /// A function type adapted from LLVM's function_ref.
  22 /// This class does not own the callable, so it is not in general safe to
  23 /// store a function.
  24 template <typename Fn> class function;
  25
  26 template <typename Ret, typename... Params> class function<Ret(Params...)> {
  27   Ret (*callback)(intptr_t callable, Params... params) = nullptr;
  28   intptr_t callable;
  29
  30   template <typename Callable>
  31   LIBC_INLINE static Ret callback_fn(intptr_t callable, Params... params) {
  32     return (*reinterpret_cast<Callable *>(callable))(
  33         forward<Params>(params)...);
  34   }
  35
  36 public:
  37   LIBC_INLINE function() = default;
  38   LIBC_INLINE function(decltype(nullptr)) {}
  39   LIBC_INLINE ~function() = default;
  40
  41   template <typename Callable>
  42   LIBC_INLINE function(
  43       Callable &&callable,
  44       // This is not the copy-constructor.
  45       enable_if_t<!is_same<remove_cvref_t<Callable>, function>::value> * =
  46           nullptr,
  47       // Functor must be callable and return a suitable type.
  48       enable_if_t<is_void_v<Ret> ||
  49                   is_convertible_v<
  50                       decltype(declval<Callable>()(declval<Params>()...)), Ret>>
  51           * = nullptr)
  52       : callback(callback_fn<remove_reference_t<Callable>>),
  53         callable(reinterpret_cast<intptr_t>(&callable)) {}
  54
  55   LIBC_INLINE Ret operator()(Params... params) const {
  56     return callback(callable, forward<Params>(params)...);
  57   }
  58
  59   LIBC_INLINE explicit operator bool() const { return callback; }
  60 };
  61
  62 } // namespace cpp
  63 } // namespace __llvm_libc
  64
  65 #endif // LLVM_LIBC_SRC_SUPPORT_CPP_FUNCTIONAL_H