├── .gitignore ├── coroutine.hpp ├── README.md ├── coroutine.h └── LICENSE /.gitignore: -------------------------------------------------------------------------------- 1 | # Prerequisites 2 | *.d 3 | 4 | # Object files 5 | *.o 6 | *.ko 7 | *.obj 8 | *.elf 9 | 10 | # Linker output 11 | *.ilk 12 | *.map 13 | *.exp 14 | 15 | # Precompiled Headers 16 | *.gch 17 | *.pch 18 | 19 | # Libraries 20 | *.lib 21 | *.a 22 | *.la 23 | *.lo 24 | 25 | # Shared objects (inc. Windows DLLs) 26 | *.dll 27 | *.so 28 | *.so.* 29 | *.dylib 30 | 31 | # Executables 32 | *.exe 33 | *.out 34 | *.app 35 | *.i*86 36 | *.x86_64 37 | *.hex 38 | 39 | # Debug files 40 | *.dSYM/ 41 | *.su 42 | *.idb 43 | *.pdb 44 | 45 | # Kernel Module Compile Results 46 | *.mod* 47 | *.cmd 48 | .tmp_versions/ 49 | modules.order 50 | Module.symvers 51 | Mkfile.old 52 | dkms.conf 53 | -------------------------------------------------------------------------------- /coroutine.hpp: -------------------------------------------------------------------------------- 1 | /**@file 2 | * This header file contains the C++ implementation of stackless coroutines. 3 | * 4 | * @see coroutine.h 5 | * 6 | * @copyright 2018-2019 Lely Industries N.V. 7 | * 8 | * @author J. S. Seldenthuis 9 | * 10 | * Licensed under the Apache License, Version 2.0 (the "License"); 11 | * you may not use this file except in compliance with the License. 12 | * You may obtain a copy of the License at 13 | * 14 | * http://www.apache.org/licenses/LICENSE-2.0 15 | * 16 | * Unless required by applicable law or agreed to in writing, software 17 | * distributed under the License is distributed on an "AS IS" BASIS, 18 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 19 | * See the License for the specific language governing permissions and 20 | * limitations under the License. 21 | */ 22 | 23 | #ifndef COROUTINE_HPP_ 24 | #define COROUTINE_HPP_ 25 | 26 | #include "coroutine.h" 27 | 28 | #undef co_restart 29 | #define co_restart(ctx) co_restart__(to_co_ctx(ctx)) 30 | 31 | #undef co_is_ready 32 | #define co_is_ready(ctx) co_is_ready__(to_co_ctx(ctx)) 33 | 34 | #undef co_reenter 35 | #define co_reenter(ctx) co_reenter__(to_co_ctx(ctx)) 36 | 37 | /** 38 | * The parent class for function objects used as stackless coroutines. Derived 39 | * classes use `co_reenter (this) { ... }` in their implementation of 40 | * `operator()` to define the body of the coroutine. Note that local variables 41 | * are not stored between invocations. It is recommended to use data members for 42 | * variables that need to be restored. 43 | */ 44 | class Coroutine { 45 | public: 46 | /** 47 | * Resets the stackless coroutine so the next invocation starts at the 48 | * beginning. 49 | */ 50 | void restart() noexcept { co_restart(this); } 51 | 52 | /// Returns true if the stackless coroutine has finished. 53 | bool is_ready() const noexcept { return ctx_.label == -1; } 54 | 55 | /// Returns true if the stackless coroutine is the parent of a fork. 56 | bool is_parent() const noexcept { return !is_child(); } 57 | 58 | /// Returns true if the stackless coroutine is the child of a fork. 59 | bool is_child() const noexcept { return ctx_.label < -1; } 60 | 61 | private: 62 | co_ctx_t ctx_ CO_CTX_INIT; 63 | 64 | friend co_ctx_t* to_co_ctx(Coroutine* coro) noexcept { return &coro->ctx_; } 65 | friend co_ctx_t* to_co_ctx(Coroutine& coro) noexcept { return &coro.ctx_; } 66 | }; 67 | 68 | inline co_ctx_t* to_co_ctx(co_ctx_t* ctx) noexcept { return ctx; } 69 | 70 | #endif // !COROUTINE_HPP_ 71 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # coroutine 2 | 3 | This is a header-only stackless coroutine implementation in standard C99 and 4 | C++11. [coroutine.h] contains a C adaptation of the C++ stackless coroutine from 5 | Boost.Asio 6 | by Christopher M. Kohlhoff. This is itself a variant of Simon Tatham's 7 | Coroutines in C, 8 | which was inspired by 9 | Duff's device. The 10 | API is designed to be a more powerfull version of 11 | Protothreads with a more natural 12 | syntax. 13 | 14 | The implementation (ab)uses the switch statement. It is therefore not 15 | possible to yield from a coroutine from within a nested switch statement. 16 | 17 | Since the implementation is stackless, variables local to the coroutine are 18 | not stored between invocations. In C++, this drawback can be partially 19 | mitigated by implementing the coroutine as a function object (see 20 | [coroutine.hpp]) and making all local variables (private) data members. 21 | 22 | ## API 23 | 24 | * `co_reenter(ctx)`: 25 | Defines the body of a stackless coroutine. When the body is executed at 26 | runtime, control jumps to the location immediately following the last 27 | `co_yield` or `co_fork` statement. 28 | 29 | Note that a function MUST NOT contain multiple `co_reenter` expressions with 30 | the same context. 31 | 32 | * `co_yield `: 33 | Stores the context of the current stackless coroutine, evaluates the 34 | expression following the `co_yield` keyword, if any, and exits the scope of 35 | the #co_reenter statement. `co_yield break` terminates the coroutine. 36 | `co_yield continue` is equivalent to `co_yield`. 37 | 38 | A `co_yield` expression is valid only within a `co_reenter` statement. Since 39 | `co_reenter` is implemented using a `switch` statement, `co_yield` CANNOT be 40 | used from within a nested `switch` statement. 41 | 42 | * `co_fork `: 43 | "Forks" a coroutine and executes the expression following the `co_fork` 44 | keyword as a child. This expression will typically create a copy of the 45 | coroutine context. After the expression completes, the coroutine continues and 46 | as a parent. If the coroutine is reentered with (the copy of) the context 47 | created by `co_fork`, the coroutine continues as a child until the next 48 | `co_yield` statement. 49 | 50 | See [coroutine.h] for an example of `co_fork`. 51 | 52 | ## C99 example 53 | 54 | ```c 55 | #include "coroutine.h" 56 | 57 | void my_coroutine(co_ctx_t* ctx) { 58 | ... 59 | // statements executed on every invocation of my_coroutine() 60 | ... 61 | co_reenter (ctx) { 62 | assert(!co_is_ready(ctx)); 63 | ... 64 | // statements executed on the first invocation of 65 | // my_coroutine() 66 | ... 67 | // Store the context and exit the scope of the co_reenter 68 | // statement. 69 | co_yield; 70 | ... 71 | // statements executed on the second invocation of 72 | // my_coroutine() 73 | ... 74 | co_yield; 75 | ... 76 | // statements executed on the third invocation of 77 | // my_coroutine() 78 | ... 79 | } 80 | ... 81 | // statements executed on every invocation of my_coroutine() (unless the 82 | // function returns early) 83 | ... 84 | } 85 | ``` 86 | 87 | ## C++11 example 88 | 89 | ```cpp 90 | #include "coroutine.hpp" 91 | 92 | class MyCoroutine : public Coroutine { 93 | public: 94 | void operator()() { 95 | ... 96 | // statements executed on every invocation 97 | ... 98 | co_reenter (this) { 99 | ... 100 | // statements executed on the first invocation 101 | ... 102 | // Store the context and exit the scope of the co_reenter statement. 103 | co_yield; 104 | ... 105 | // statements executed on the second invocation 106 | ... 107 | co_yield; 108 | ... 109 | // statements executed on the third invocation 110 | ... 111 | } 112 | ... 113 | // statements executed on every invocation (unless this function returns 114 | // early) 115 | ... 116 | } 117 | }; 118 | ``` 119 | 120 | [coroutine.h]: coroutine.h 121 | [coroutine.hpp]: coroutine.hpp 122 | -------------------------------------------------------------------------------- /coroutine.h: -------------------------------------------------------------------------------- 1 | /**@file 2 | * This header file contains a stackless coroutine implementation. The 3 | * implementation is pure and compliant C99 and does not require any part of the 4 | * standard library. It is an adaptation of the C++ stackless coroutine from 5 | * Boost.Asio 6 | * by Christopher M. Kohlhoff. This is itself a variant of Simon Tatham's 7 | * Coroutines in C, 8 | * which was inspired by 9 | * Duff's device. 10 | * 11 | * The implementation (ab)uses the switch statement. It is therefore not 12 | * possible to yield from a coroutine from within a nested switch statement. 13 | * 14 | * Since the implementation is stackless, variables local to the coroutine are 15 | * not stored between invocations. In C++, this drawback can be partially 16 | * mitigated by implementing the coroutine as a function object and making all 17 | * local variables (private) data members. 18 | * 19 | * @copyright 2018-2019 Lely Industries N.V. 20 | * 21 | * @author J. S. Seldenthuis 22 | * 23 | * Licensed under the Apache License, Version 2.0 (the "License"); 24 | * you may not use this file except in compliance with the License. 25 | * You may obtain a copy of the License at 26 | * 27 | * http://www.apache.org/licenses/LICENSE-2.0 28 | * 29 | * Unless required by applicable law or agreed to in writing, software 30 | * distributed under the License is distributed on an "AS IS" BASIS, 31 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 32 | * See the License for the specific language governing permissions and 33 | * limitations under the License. 34 | */ 35 | 36 | #ifndef COROUTINE_H_ 37 | #define COROUTINE_H_ 38 | 39 | #ifndef CO_LABEL_TYPE 40 | /** 41 | * The type used to store the label (i.e., program counter) of a stackless 42 | * coroutine. A smaller type may be used in constrained environments, especially 43 | * if the `__COUNTER__` macro is available. 44 | */ 45 | #define CO_LABEL_TYPE int 46 | #endif 47 | 48 | /** 49 | * The type holding the context (i.e., program counter) of a stackless 50 | * coroutine. 51 | */ 52 | typedef struct { 53 | CO_LABEL_TYPE label; 54 | } co_ctx_t; 55 | 56 | /// The static initializer for #co_ctx_t. 57 | #define CO_CTX_INIT \ 58 | { \ 59 | 0 \ 60 | } 61 | 62 | /// Resets a stackless coroutine so the next invocation starts at the beginning. 63 | #define co_restart(ctx) co_restart__(ctx) 64 | #define co_restart__(ctx) ((void)((ctx)->label = 0)) 65 | 66 | /// Returns 1 if the stackless coroutine has finished. 67 | #define co_is_ready(ctx) co_is_ready__(ctx) 68 | #define co_is_ready__(ctx) ((ctx)->label == -1) 69 | 70 | /** 71 | * Defines the body of a stackless coroutine. When the body is executed at 72 | * runtime, control jumps to the location immediately following the last 73 | * #co_yield or #co_fork statement. 74 | * 75 | * Note that a function MUST NOT contain multiple `co_reenter` expressions with 76 | * the same context. 77 | * 78 | * ```{.c} 79 | * void my_coroutine(co_ctx_t* ctx) { 80 | * ... 81 | * // statements executed on every invocation of my_coroutine() 82 | * ... 83 | * co_reenter (ctx) { 84 | * assert(!co_is_ready(ctx)); 85 | * ... 86 | * // statements executed on the first invocation of 87 | * // my_coroutine() 88 | * ... 89 | * // Store the context and exit the scope of the co_reenter 90 | * // statement. 91 | * co_yield; 92 | * ... 93 | * // statements executed on the second invocation of 94 | * // my_coroutine() 95 | * ... 96 | * co_yield; 97 | * ... 98 | * // statements executed on the third invocation of 99 | * // my_coroutine() 100 | * ... 101 | * } 102 | * ... 103 | * // statements executed on every invocation of my_coroutine() (unless 104 | * // the function returns early) 105 | * ... 106 | * } 107 | * ``` 108 | */ 109 | #define co_reenter(ctx) co_reenter__(ctx) 110 | #define co_reenter__(ctx) \ 111 | for (CO_LABEL_TYPE *const _co_label_ = &(ctx)->label; \ 112 | *_co_label_ != -1; *_co_label_ = -1) \ 113 | if (0) { \ 114 | goto _co_continue_; \ 115 | _co_continue_: \ 116 | continue; \ 117 | } else if (0) { \ 118 | goto _co_break_; \ 119 | _co_break_: \ 120 | break; \ 121 | } else \ 122 | switch (*_co_label_) \ 123 | case 0: 124 | 125 | #ifdef __COUNTER__ 126 | #define co_label__ (__COUNTER__ + 1) 127 | #else 128 | #define co_label__ __LINE__ 129 | #endif 130 | 131 | /** 132 | * Stores the context of the current stackless coroutine, evaluates the 133 | * expression following the `co_yield` keyword, if any, and exits the scope of 134 | * the #co_reenter statement. `co_yield break` terminates the coroutine (i.e., 135 | * after this statement, co_is_ready() returns 1). `co_yield continue` is 136 | * equivalent to `co_yield`. 137 | * 138 | * A `co_yield` expression is valid only within a #co_reenter statement. Since 139 | * #co_reenter is implemented using a `switch` statement, `co_yield` CANNOT be 140 | * used from within a nested `switch` statement. 141 | */ 142 | #define co_yield co_yield__(co_label__) 143 | // clang-format off 144 | #define co_yield__(label) \ 145 | for (*_co_label_ = (label);;) \ 146 | if (0) { \ 147 | case (label): \ 148 | break; \ 149 | } else \ 150 | switch (0) \ 151 | for (;;) \ 152 | if (1) \ 153 | goto _co_continue_; \ 154 | else \ 155 | for (;;) \ 156 | if (1) \ 157 | goto _co_break_; \ 158 | else /* falls through */ \ 159 | case 0: 160 | // clang-format on 161 | 162 | /** 163 | * "Forks" a coroutine and executes the expression following the `co_fork` 164 | * keyword as a child (i.e., co_is_child() returns 1). This expression will 165 | * typically create a copy of the coroutine context. After the expression 166 | * completes, the coroutine continues and co_is_parent() returns 1. If the 167 | * coroutine is reentered with (the copy of) the context created by `co_fork`, 168 | * co_is_child() returns 1 until the next `co_yield` statement. 169 | * 170 | * For example: 171 | * ```{.c} 172 | * co_reenter (ctx) { 173 | * do { 174 | * ... 175 | * // statements executed by parent 176 | * ... 177 | * co_fork create_copy_and_do_something(ctx); 178 | * } while (co_is_parent()); 179 | * // This is where co_reenter resumes with the context from 180 | * // create_copy_and_do_something(). 181 | * assert(co_is_child()); 182 | * ... 183 | * // statements executed by child 184 | * ... 185 | * co_yield; 186 | * // After a co_yield statement a coroutine is always considered a 187 | * // parent. 188 | * assert(co_is_parent()); 189 | * } 190 | * ``` 191 | * 192 | * This works especially well with function objects in C++. The canonical use 193 | * case is a server accepting and handling connections: 194 | * ```{.cpp} 195 | * class Server : public Coroutine { 196 | * public: 197 | * void operator()(int s) { 198 | * co_reenter (this) { 199 | * do { 200 | * // Perform an asynchronous accept on a socket. When a connection is 201 | * // accepted, async_accept() invokes this function object with the 202 | * // accepted socket. 203 | * co_yield async_accept(socket_, *this); 204 | * // Create a copy of the current coroutine function object to handle 205 | * // the connection, while the parent accepts the next incoming 206 | * // connection. 207 | * co_fork Server(*this)(s); 208 | * } while (is_parent()); 209 | * // Handle the connection. 210 | * co_yield async_read(s, ..., *this); 211 | * } 212 | * } 213 | * private: 214 | * // The socket used to listen for incoming connections. 215 | * int socket_; 216 | * }; 217 | * ``` 218 | */ 219 | #define co_fork co_fork__(co_label__) 220 | #define co_fork__(label) \ 221 | for (*_co_label_ = -(label)-1;; *_co_label_ = (label)) \ 222 | if (_co_label_ == (label)) { \ 223 | case -(label)-1: break; \ 224 | } else 225 | 226 | /// Returns 1 if the calling stackless coroutine is the parent of a fork. 227 | #define co_is_parent() (!co_is_child()) 228 | 229 | /// Returns 1 if the calling stackless coroutine is the child of a fork. 230 | #define co_is_child() (*_co_label_ < -1) 231 | 232 | #endif // !COROUTINE_H_ 233 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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