Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2020 The WebRTC Project Authors. All rights reserved. |
| 3 | * |
| 4 | * Use of this source code is governed by a BSD-style license |
| 5 | * that can be found in the LICENSE file in the root of the source |
| 6 | * tree. An additional intellectual property rights grant can be found |
| 7 | * in the file PATENTS. All contributing project authors may |
| 8 | * be found in the AUTHORS file in the root of the source tree. |
| 9 | */ |
| 10 | |
Karl Wiberg | 70026f9 | 2020-09-18 08:03:16 | [diff] [blame] | 11 | #ifndef RTC_BASE_UNTYPED_FUNCTION_H_ |
| 12 | #define RTC_BASE_UNTYPED_FUNCTION_H_ |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 13 | |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 14 | #include <cstddef> |
| 15 | #include <cstring> |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 16 | #include <memory> |
| 17 | #include <type_traits> |
| 18 | #include <utility> |
| 19 | |
| 20 | #include "rtc_base/system/assume.h" |
| 21 | |
| 22 | namespace webrtc { |
| 23 | namespace webrtc_function_impl { |
| 24 | |
| 25 | using FunVoid = void(); |
| 26 | |
Karl Wiberg | 84ba18a | 2020-10-06 10:10:59 | [diff] [blame] | 27 | // Inline storage size is this many machine words. |
| 28 | enum : size_t { kInlineStorageWords = 4 }; |
| 29 | |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 30 | union VoidUnion { |
| 31 | void* void_ptr; |
| 32 | FunVoid* fun_ptr; |
Karl Wiberg | 84ba18a | 2020-10-06 10:10:59 | [diff] [blame] | 33 | typename std::aligned_storage<kInlineStorageWords * sizeof(uintptr_t)>::type |
| 34 | inline_storage; |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 35 | }; |
| 36 | |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 37 | // Returns the number of elements of the `inline_storage` array required to |
| 38 | // store an object of type T. |
| 39 | template <typename T> |
| 40 | constexpr size_t InlineStorageSize() { |
| 41 | // sizeof(T) / sizeof(uintptr_t), but rounded up. |
| 42 | return (sizeof(T) + sizeof(uintptr_t) - 1) / sizeof(uintptr_t); |
| 43 | } |
| 44 | |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 45 | template <typename T> |
| 46 | struct CallHelpers; |
| 47 | template <typename RetT, typename... ArgT> |
| 48 | struct CallHelpers<RetT(ArgT...)> { |
Karl Wiberg | 804db2d | 2020-09-15 09:07:10 | [diff] [blame] | 49 | // Return type of the three helpers below. |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 50 | using return_type = RetT; |
Karl Wiberg | 804db2d | 2020-09-15 09:07:10 | [diff] [blame] | 51 | // Complete function type of the three helpers below. |
| 52 | using function_type = RetT(VoidUnion*, ArgT...); |
| 53 | // Helper for calling the `void_ptr` case of VoidUnion. |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 54 | template <typename F> |
| 55 | static RetT CallVoidPtr(VoidUnion* vu, ArgT... args) { |
| 56 | return (*static_cast<F*>(vu->void_ptr))(std::forward<ArgT>(args)...); |
| 57 | } |
Karl Wiberg | 804db2d | 2020-09-15 09:07:10 | [diff] [blame] | 58 | // Helper for calling the `fun_ptr` case of VoidUnion. |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 59 | static RetT CallFunPtr(VoidUnion* vu, ArgT... args) { |
| 60 | return (reinterpret_cast<RetT (*)(ArgT...)>(vu->fun_ptr))( |
| 61 | std::forward<ArgT>(args)...); |
| 62 | } |
Karl Wiberg | 804db2d | 2020-09-15 09:07:10 | [diff] [blame] | 63 | // Helper for calling the `inline_storage` case of VoidUnion. |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 64 | template <typename F> |
| 65 | static RetT CallInlineStorage(VoidUnion* vu, ArgT... args) { |
| 66 | return (*reinterpret_cast<F*>(&vu->inline_storage))( |
| 67 | std::forward<ArgT>(args)...); |
| 68 | } |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 69 | }; |
| 70 | |
| 71 | } // namespace webrtc_function_impl |
| 72 | |
| 73 | // A class that holds (and owns) any callable. The same function call signature |
| 74 | // must be provided when constructing and calling the object. |
| 75 | // |
| 76 | // The point of not having the call signature as a class template parameter is |
| 77 | // to have one single concrete type for all signatures; this reduces binary |
| 78 | // size. |
| 79 | class UntypedFunction final { |
| 80 | public: |
Karl Wiberg | 84ba18a | 2020-10-06 10:10:59 | [diff] [blame] | 81 | // Callables of at most this size can be stored inline, if they are trivial. |
| 82 | // (Useful in tests and benchmarks; avoid using this in production code.) |
| 83 | enum : size_t { |
| 84 | kInlineStorageSize = sizeof(webrtc_function_impl::VoidUnion::inline_storage) |
| 85 | }; |
| 86 | static_assert(kInlineStorageSize == |
| 87 | webrtc_function_impl::kInlineStorageWords * |
| 88 | sizeof(uintptr_t), |
| 89 | ""); |
| 90 | |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 91 | // The *UntypedFunctionArgs structs are used to transfer arguments from |
| 92 | // PrepareArgs() to Create(). They are trivial, but may own heap allocations, |
| 93 | // so make sure to pass them to Create() exactly once! |
| 94 | // |
| 95 | // The point of doing Create(PrepareArgs(foo)) instead of just Create(foo) is |
| 96 | // to separate the code that has to be inlined (PrepareArgs) from the code |
| 97 | // that can be noninlined (Create); the *UntypedFunctionArgs types are |
| 98 | // designed to efficiently carry the required information from one to the |
| 99 | // other. |
| 100 | template <size_t N> |
| 101 | struct TrivialUntypedFunctionArgs { |
Karl Wiberg | 84ba18a | 2020-10-06 10:10:59 | [diff] [blame] | 102 | static_assert(N >= 1, ""); |
| 103 | static_assert(N <= webrtc_function_impl::kInlineStorageWords, ""); |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 104 | // We use an uintptr_t array here instead of std::aligned_storage, because |
| 105 | // the former can be efficiently passed in registers when using |
| 106 | // TrivialUntypedFunctionArgs as a function argument. (We can't do the same |
| 107 | // in VoidUnion, because std::aligned_storage but not uintptr_t can be |
| 108 | // legally reinterpret_casted to arbitrary types. |
| 109 | // TrivialUntypedFunctionArgs, on the other hand, only needs to handle |
| 110 | // placement new and memcpy.) |
| 111 | alignas(std::max_align_t) uintptr_t inline_storage[N]; |
| 112 | webrtc_function_impl::FunVoid* call; |
| 113 | }; |
| 114 | struct NontrivialUntypedFunctionArgs { |
| 115 | void* void_ptr; |
| 116 | webrtc_function_impl::FunVoid* call; |
| 117 | void (*del)(webrtc_function_impl::VoidUnion*); |
| 118 | }; |
| 119 | struct FunctionPointerUntypedFunctionArgs { |
| 120 | webrtc_function_impl::FunVoid* fun_ptr; |
| 121 | webrtc_function_impl::FunVoid* call; |
| 122 | }; |
| 123 | |
| 124 | // Create function for lambdas and other callables that are trivial and small; |
| 125 | // it accepts every type of argument except those noted in its enable_if call. |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 126 | template < |
| 127 | typename Signature, |
| 128 | typename F, |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 129 | typename F_deref = typename std::remove_reference<F>::type, |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 130 | typename std::enable_if< |
| 131 | // Not for function pointers; we have another overload for that below. |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 132 | !std::is_function< |
| 133 | typename std::remove_pointer<F_deref>::type>::value && |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 134 | |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 135 | // Not for nullptr; we have a constructor for that below. |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 136 | !std::is_same<std::nullptr_t, |
| 137 | typename std::remove_cv<F>::type>::value && |
| 138 | |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 139 | // Not for UntypedFunction objects; use move construction or |
| 140 | // assignment. |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 141 | !std::is_same<UntypedFunction, |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 142 | typename std::remove_cv<F_deref>::type>::value && |
| 143 | |
Karl Wiberg | 84ba18a | 2020-10-06 10:10:59 | [diff] [blame] | 144 | // Only for trivial callables that will fit in inline storage. |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 145 | std::is_trivially_move_constructible<F_deref>::value && |
| 146 | std::is_trivially_destructible<F_deref>::value && |
Karl Wiberg | 84ba18a | 2020-10-06 10:10:59 | [diff] [blame] | 147 | sizeof(F_deref) <= kInlineStorageSize>::type* = nullptr, |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 148 | size_t InlineSize = webrtc_function_impl::InlineStorageSize<F_deref>()> |
| 149 | static TrivialUntypedFunctionArgs<InlineSize> PrepareArgs(F&& f) { |
| 150 | // The callable is trivial and small enough, so we just store its bytes |
| 151 | // in the inline storage. |
| 152 | TrivialUntypedFunctionArgs<InlineSize> args; |
| 153 | new (&args.inline_storage) F_deref(std::forward<F>(f)); |
| 154 | args.call = reinterpret_cast<webrtc_function_impl::FunVoid*>( |
| 155 | webrtc_function_impl::CallHelpers< |
| 156 | Signature>::template CallInlineStorage<F_deref>); |
| 157 | return args; |
| 158 | } |
| 159 | template <size_t InlineSize> |
| 160 | static UntypedFunction Create(TrivialUntypedFunctionArgs<InlineSize> args) { |
| 161 | webrtc_function_impl::VoidUnion vu; |
| 162 | std::memcpy(&vu.inline_storage, args.inline_storage, |
| 163 | sizeof(args.inline_storage)); |
| 164 | return UntypedFunction(vu, args.call, nullptr); |
| 165 | } |
| 166 | |
| 167 | // Create function for lambdas and other callables that are nontrivial or |
| 168 | // large; it accepts every type of argument except those noted in its |
| 169 | // enable_if call. |
Karl Wiberg | 84ba18a | 2020-10-06 10:10:59 | [diff] [blame] | 170 | template <typename Signature, |
| 171 | typename F, |
| 172 | typename F_deref = typename std::remove_reference<F>::type, |
| 173 | typename std::enable_if< |
| 174 | // Not for function pointers; we have another overload for that |
| 175 | // below. |
| 176 | !std::is_function< |
| 177 | typename std::remove_pointer<F_deref>::type>::value && |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 178 | |
Karl Wiberg | 84ba18a | 2020-10-06 10:10:59 | [diff] [blame] | 179 | // Not for nullptr; we have a constructor for that below. |
| 180 | !std::is_same<std::nullptr_t, |
| 181 | typename std::remove_cv<F>::type>::value && |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 182 | |
Karl Wiberg | 84ba18a | 2020-10-06 10:10:59 | [diff] [blame] | 183 | // Not for UntypedFunction objects; use move construction or |
| 184 | // assignment. |
| 185 | !std::is_same<UntypedFunction, |
| 186 | typename std::remove_cv<F_deref>::type>::value && |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 187 | |
Karl Wiberg | 84ba18a | 2020-10-06 10:10:59 | [diff] [blame] | 188 | // Only for nontrivial callables, or callables that won't fit in |
| 189 | // inline storage. |
| 190 | !(std::is_trivially_move_constructible<F_deref>::value && |
| 191 | std::is_trivially_destructible<F_deref>::value && |
| 192 | sizeof(F_deref) <= kInlineStorageSize)>::type* = nullptr> |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 193 | static NontrivialUntypedFunctionArgs PrepareArgs(F&& f) { |
| 194 | // The callable is either nontrivial or too large, so we can't keep it |
| 195 | // in the inline storage; use the heap instead. |
| 196 | NontrivialUntypedFunctionArgs args; |
| 197 | args.void_ptr = new F_deref(std::forward<F>(f)); |
| 198 | args.call = reinterpret_cast<webrtc_function_impl::FunVoid*>( |
| 199 | webrtc_function_impl::CallHelpers<Signature>::template CallVoidPtr< |
| 200 | F_deref>); |
| 201 | args.del = static_cast<void (*)(webrtc_function_impl::VoidUnion*)>( |
| 202 | [](webrtc_function_impl::VoidUnion* vu) { |
| 203 | // Assuming that this pointer isn't null allows the |
| 204 | // compiler to eliminate a null check in the (inlined) |
| 205 | // delete operation. |
| 206 | RTC_ASSUME(vu->void_ptr != nullptr); |
| 207 | delete reinterpret_cast<F_deref*>(vu->void_ptr); |
| 208 | }); |
| 209 | return args; |
| 210 | } |
| 211 | static UntypedFunction Create(NontrivialUntypedFunctionArgs args) { |
| 212 | webrtc_function_impl::VoidUnion vu; |
| 213 | vu.void_ptr = args.void_ptr; |
| 214 | return UntypedFunction(vu, args.call, args.del); |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 215 | } |
| 216 | |
| 217 | // Create function that accepts function pointers. If the argument is null, |
| 218 | // the result is an empty UntypedFunction. |
| 219 | template <typename Signature> |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 220 | static FunctionPointerUntypedFunctionArgs PrepareArgs(Signature* f) { |
| 221 | FunctionPointerUntypedFunctionArgs args; |
| 222 | args.fun_ptr = reinterpret_cast<webrtc_function_impl::FunVoid*>(f); |
| 223 | args.call = reinterpret_cast<webrtc_function_impl::FunVoid*>( |
| 224 | webrtc_function_impl::CallHelpers<Signature>::CallFunPtr); |
| 225 | return args; |
| 226 | } |
| 227 | static UntypedFunction Create(FunctionPointerUntypedFunctionArgs args) { |
Karl Wiberg | 78e9acd | 2020-09-15 09:06:34 | [diff] [blame] | 228 | webrtc_function_impl::VoidUnion vu; |
Karl Wiberg | d2c6967 | 2020-09-29 11:55:13 | [diff] [blame] | 229 | vu.fun_ptr = args.fun_ptr; |
| 230 | return UntypedFunction(vu, args.fun_ptr == nullptr ? nullptr : args.call, |
| 231 | nullptr); |
| 232 | } |
| 233 | |
| 234 | // Prepares arguments and creates an UntypedFunction in one go. |
| 235 | template <typename Signature, typename F> |
| 236 | static UntypedFunction Create(F&& f) { |
| 237 | return Create(PrepareArgs<Signature>(std::forward<F>(f))); |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 238 | } |
| 239 | |
| 240 | // Default constructor. Creates an empty UntypedFunction. |
| 241 | UntypedFunction() : call_(nullptr), delete_(nullptr) {} |
| 242 | |
Karl Wiberg | 78e9acd | 2020-09-15 09:06:34 | [diff] [blame] | 243 | // Nullptr constructor and assignment. Creates an empty UntypedFunction. |
| 244 | UntypedFunction(std::nullptr_t) // NOLINT(runtime/explicit) |
| 245 | : call_(nullptr), delete_(nullptr) {} |
| 246 | UntypedFunction& operator=(std::nullptr_t) { |
| 247 | call_ = nullptr; |
| 248 | if (delete_) { |
| 249 | delete_(&f_); |
| 250 | delete_ = nullptr; |
| 251 | } |
| 252 | return *this; |
| 253 | } |
| 254 | |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 255 | // Not copyable. |
| 256 | UntypedFunction(const UntypedFunction&) = delete; |
| 257 | UntypedFunction& operator=(const UntypedFunction&) = delete; |
| 258 | |
| 259 | // Move construction and assignment. |
| 260 | UntypedFunction(UntypedFunction&& other) |
| 261 | : f_(other.f_), call_(other.call_), delete_(other.delete_) { |
| 262 | other.delete_ = nullptr; |
| 263 | } |
| 264 | UntypedFunction& operator=(UntypedFunction&& other) { |
Karl Wiberg | 78e9acd | 2020-09-15 09:06:34 | [diff] [blame] | 265 | if (delete_) { |
| 266 | delete_(&f_); |
| 267 | } |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 268 | f_ = other.f_; |
| 269 | call_ = other.call_; |
| 270 | delete_ = other.delete_; |
| 271 | other.delete_ = nullptr; |
| 272 | return *this; |
| 273 | } |
| 274 | |
| 275 | ~UntypedFunction() { |
| 276 | if (delete_) { |
| 277 | delete_(&f_); |
| 278 | } |
| 279 | } |
| 280 | |
| 281 | friend void swap(UntypedFunction& a, UntypedFunction& b) { |
| 282 | using std::swap; |
| 283 | swap(a.f_, b.f_); |
| 284 | swap(a.call_, b.call_); |
| 285 | swap(a.delete_, b.delete_); |
| 286 | } |
| 287 | |
| 288 | // Returns true if we have a function, false if we don't (i.e., we're null). |
| 289 | explicit operator bool() const { return call_ != nullptr; } |
| 290 | |
| 291 | template <typename Signature, typename... ArgT> |
| 292 | typename webrtc_function_impl::CallHelpers<Signature>::return_type Call( |
Karl Wiberg | 78e9acd | 2020-09-15 09:06:34 | [diff] [blame] | 293 | ArgT&&... args) { |
Karl Wiberg | 804db2d | 2020-09-15 09:07:10 | [diff] [blame] | 294 | return reinterpret_cast< |
| 295 | typename webrtc_function_impl::CallHelpers<Signature>::function_type*>( |
| 296 | call_)(&f_, std::forward<ArgT>(args)...); |
Karl Wiberg | 3d452cf | 2020-09-11 14:09:46 | [diff] [blame] | 297 | } |
| 298 | |
| 299 | // Returns true iff we don't need to call a destructor. This is guaranteed |
| 300 | // to hold for a moved-from object. |
| 301 | bool IsTriviallyDestructible() { return delete_ == nullptr; } |
| 302 | |
| 303 | private: |
| 304 | UntypedFunction(webrtc_function_impl::VoidUnion f, |
| 305 | webrtc_function_impl::FunVoid* call, |
| 306 | void (*del)(webrtc_function_impl::VoidUnion*)) |
| 307 | : f_(f), call_(call), delete_(del) {} |
| 308 | |
| 309 | // The callable thing, or a pointer to it. |
| 310 | webrtc_function_impl::VoidUnion f_; |
| 311 | |
| 312 | // Pointer to a dispatch function that knows the type of the callable thing |
| 313 | // that's stored in f_, and how to call it. An UntypedFunction object is empty |
| 314 | // (null) iff call_ is null. |
| 315 | webrtc_function_impl::FunVoid* call_; |
| 316 | |
| 317 | // Pointer to a function that knows how to delete the callable thing that's |
| 318 | // stored in f_. Null if `f_` is trivially deletable. |
| 319 | void (*delete_)(webrtc_function_impl::VoidUnion*); |
| 320 | }; |
| 321 | |
| 322 | } // namespace webrtc |
| 323 | |
Karl Wiberg | 70026f9 | 2020-09-18 08:03:16 | [diff] [blame] | 324 | #endif // RTC_BASE_UNTYPED_FUNCTION_H_ |