1
2 // Copyright Oliver Kowalke 2017.
3 // Distributed under the Boost Software License, Version 1.0.
4 // (See accompanying file LICENSE_1_0.txt or copy at
5 // http://www.boost.org/LICENSE_1_0.txt)
6
7 #ifndef BOOST_CONTEXT_FIBER_H
8 #define BOOST_CONTEXT_FIBER_H
9
10 #include <boost/context/detail/config.hpp>
11
12 #include <algorithm>
13 #include <cstddef>
14 #include <cstdint>
15 #include <cstdlib>
16 #include <exception>
17 #include <functional>
18 #include <memory>
19 #include <ostream>
20 #include <tuple>
21 #include <utility>
22
23 #include <boost/assert.hpp>
24 #include <boost/config.hpp>
25 #include <boost/intrusive_ptr.hpp>
26
27 #if defined(BOOST_NO_CXX14_STD_EXCHANGE)
28 #include <boost/context/detail/exchange.hpp>
29 #endif
30 #if defined(BOOST_NO_CXX17_STD_INVOKE)
31 #include <boost/context/detail/invoke.hpp>
32 #endif
33 #include <boost/context/detail/disable_overload.hpp>
34 #include <boost/context/detail/exception.hpp>
35 #include <boost/context/detail/fcontext.hpp>
36 #include <boost/context/detail/tuple.hpp>
37 #include <boost/context/fixedsize_stack.hpp>
38 #include <boost/context/flags.hpp>
39 #include <boost/context/preallocated.hpp>
40 #include <boost/context/segmented_stack.hpp>
41 #include <boost/context/stack_context.hpp>
42
43 #ifdef BOOST_HAS_ABI_HEADERS
44 # include BOOST_ABI_PREFIX
45 #endif
46
47 #if defined(BOOST_MSVC)
48 # pragma warning(push)
49 # pragma warning(disable: 4702)
50 #endif
51
52 namespace boost {
53 namespace context {
54 namespace detail {
55
56 inline
fiber_unwind(transfer_t t)57 transfer_t fiber_unwind( transfer_t t) {
58 throw forced_unwind( t.fctx);
59 return { nullptr, nullptr };
60 }
61
62 template< typename Rec >
fiber_exit(transfer_t t)63 transfer_t fiber_exit( transfer_t t) noexcept {
64 Rec * rec = static_cast< Rec * >( t.data);
65 // destroy context stack
66 rec->deallocate();
67 return { nullptr, nullptr };
68 }
69
70 template< typename Rec >
fiber_entry(transfer_t t)71 void fiber_entry( transfer_t t) noexcept {
72 // transfer control structure to the context-stack
73 Rec * rec = static_cast< Rec * >( t.data);
74 BOOST_ASSERT( nullptr != t.fctx);
75 BOOST_ASSERT( nullptr != rec);
76 try {
77 // jump back to `create_context()`
78 t = jump_fcontext( t.fctx, nullptr);
79 // start executing
80 t.fctx = rec->run( t.fctx);
81 } catch ( forced_unwind const& ex) {
82 t = { ex.fctx, nullptr };
83 #ifndef BOOST_ASSERT_IS_VOID
84 const_cast< forced_unwind & >( ex).caught = true;
85 #endif
86 }
87 BOOST_ASSERT( nullptr != t.fctx);
88 // destroy context-stack of `this`context on next context
89 ontop_fcontext( t.fctx, rec, fiber_exit< Rec >);
90 BOOST_ASSERT_MSG( false, "context already terminated");
91 }
92
93 template< typename Ctx, typename Fn >
fiber_ontop(transfer_t t)94 transfer_t fiber_ontop( transfer_t t) {
95 BOOST_ASSERT( nullptr != t.data);
96 auto p = *static_cast< Fn * >( t.data);
97 t.data = nullptr;
98 // execute function, pass fiber via reference
99 Ctx c = p( Ctx{ t.fctx } );
100 #if defined(BOOST_NO_CXX14_STD_EXCHANGE)
101 return { exchange( c.fctx_, nullptr), nullptr };
102 #else
103 return { std::exchange( c.fctx_, nullptr), nullptr };
104 #endif
105 }
106
107 template< typename Ctx, typename StackAlloc, typename Fn >
108 class fiber_record {
109 private:
110 stack_context sctx_;
111 typename std::decay< StackAlloc >::type salloc_;
112 typename std::decay< Fn >::type fn_;
113
destroy(fiber_record * p)114 static void destroy( fiber_record * p) noexcept {
115 typename std::decay< StackAlloc >::type salloc = std::move( p->salloc_);
116 stack_context sctx = p->sctx_;
117 // deallocate fiber_record
118 p->~fiber_record();
119 // destroy stack with stack allocator
120 salloc.deallocate( sctx);
121 }
122
123 public:
fiber_record(stack_context sctx,StackAlloc && salloc,Fn && fn)124 fiber_record( stack_context sctx, StackAlloc && salloc,
125 Fn && fn) noexcept :
126 sctx_( sctx),
127 salloc_( std::forward< StackAlloc >( salloc)),
128 fn_( std::forward< Fn >( fn) ) {
129 }
130
131 fiber_record( fiber_record const&) = delete;
132 fiber_record & operator=( fiber_record const&) = delete;
133
deallocate()134 void deallocate() noexcept {
135 destroy( this);
136 }
137
run(fcontext_t fctx)138 fcontext_t run( fcontext_t fctx) {
139 // invoke context-function
140 #if defined(BOOST_NO_CXX17_STD_INVOKE)
141 Ctx c = boost::context::detail::invoke( fn_, Ctx{ fctx } );
142 #else
143 Ctx c = std::invoke( fn_, Ctx{ fctx } );
144 #endif
145 #if defined(BOOST_NO_CXX14_STD_EXCHANGE)
146 return exchange( c.fctx_, nullptr);
147 #else
148 return std::exchange( c.fctx_, nullptr);
149 #endif
150 }
151 };
152
153 template< typename Record, typename StackAlloc, typename Fn >
create_fiber1(StackAlloc && salloc,Fn && fn)154 fcontext_t create_fiber1( StackAlloc && salloc, Fn && fn) {
155 auto sctx = salloc.allocate();
156 // reserve space for control structure
157 void * storage = reinterpret_cast< void * >(
158 ( reinterpret_cast< uintptr_t >( sctx.sp) - static_cast< uintptr_t >( sizeof( Record) ) )
159 & ~static_cast< uintptr_t >( 0xff) );
160 // placment new for control structure on context stack
161 Record * record = new ( storage) Record{
162 sctx, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) };
163 // 64byte gab between control structure and stack top
164 // should be 16byte aligned
165 void * stack_top = reinterpret_cast< void * >(
166 reinterpret_cast< uintptr_t >( storage) - static_cast< uintptr_t >( 64) );
167 void * stack_bottom = reinterpret_cast< void * >(
168 reinterpret_cast< uintptr_t >( sctx.sp) - static_cast< uintptr_t >( sctx.size) );
169 // create fast-context
170 const std::size_t size = reinterpret_cast< uintptr_t >( stack_top) - reinterpret_cast< uintptr_t >( stack_bottom);
171 const fcontext_t fctx = make_fcontext( stack_top, size, & fiber_entry< Record >);
172 BOOST_ASSERT( nullptr != fctx);
173 // transfer control structure to context-stack
174 return jump_fcontext( fctx, record).fctx;
175 }
176
177 template< typename Record, typename StackAlloc, typename Fn >
create_fiber2(preallocated palloc,StackAlloc && salloc,Fn && fn)178 fcontext_t create_fiber2( preallocated palloc, StackAlloc && salloc, Fn && fn) {
179 // reserve space for control structure
180 void * storage = reinterpret_cast< void * >(
181 ( reinterpret_cast< uintptr_t >( palloc.sp) - static_cast< uintptr_t >( sizeof( Record) ) )
182 & ~ static_cast< uintptr_t >( 0xff) );
183 // placment new for control structure on context-stack
184 Record * record = new ( storage) Record{
185 palloc.sctx, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) };
186 // 64byte gab between control structure and stack top
187 void * stack_top = reinterpret_cast< void * >(
188 reinterpret_cast< uintptr_t >( storage) - static_cast< uintptr_t >( 64) );
189 void * stack_bottom = reinterpret_cast< void * >(
190 reinterpret_cast< uintptr_t >( palloc.sctx.sp) - static_cast< uintptr_t >( palloc.sctx.size) );
191 // create fast-context
192 const std::size_t size = reinterpret_cast< uintptr_t >( stack_top) - reinterpret_cast< uintptr_t >( stack_bottom);
193 const fcontext_t fctx = make_fcontext( stack_top, size, & fiber_entry< Record >);
194 BOOST_ASSERT( nullptr != fctx);
195 // transfer control structure to context-stack
196 return jump_fcontext( fctx, record).fctx;
197 }
198
199 }
200
201 class fiber {
202 private:
203 template< typename Ctx, typename StackAlloc, typename Fn >
204 friend class detail::fiber_record;
205
206 template< typename Ctx, typename Fn >
207 friend detail::transfer_t
208 detail::fiber_ontop( detail::transfer_t);
209
210 template< typename StackAlloc, typename Fn >
211 friend fiber
212 callcc( std::allocator_arg_t, StackAlloc &&, Fn &&);
213
214 template< typename StackAlloc, typename Fn >
215 friend fiber
216 callcc( std::allocator_arg_t, preallocated, StackAlloc &&, Fn &&);
217
218 detail::fcontext_t fctx_{ nullptr };
219
fiber(detail::fcontext_t fctx)220 fiber( detail::fcontext_t fctx) noexcept :
221 fctx_{ fctx } {
222 }
223
224 public:
225 fiber() noexcept = default;
226
227 template< typename Fn, typename = detail::disable_overload< fiber, Fn > >
fiber(Fn && fn)228 fiber( Fn && fn) :
229 fiber{ std::allocator_arg, fixedsize_stack(), std::forward< Fn >( fn) } {
230 }
231
232 template< typename StackAlloc, typename Fn >
fiber(std::allocator_arg_t,StackAlloc && salloc,Fn && fn)233 fiber( std::allocator_arg_t, StackAlloc && salloc, Fn && fn) :
234 fctx_{ detail::create_fiber1< detail::fiber_record< fiber, StackAlloc, Fn > >(
235 std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) ) } {
236 }
237
238 template< typename StackAlloc, typename Fn >
fiber(std::allocator_arg_t,preallocated palloc,StackAlloc && salloc,Fn && fn)239 fiber( std::allocator_arg_t, preallocated palloc, StackAlloc && salloc, Fn && fn) :
240 fctx_{ detail::create_fiber2< detail::fiber_record< fiber, StackAlloc, Fn > >(
241 palloc, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) ) } {
242 }
243
244 #if defined(BOOST_USE_SEGMENTED_STACKS)
245 template< typename Fn >
246 fiber( std::allocator_arg_t, segmented_stack, Fn &&);
247
248 template< typename StackAlloc, typename Fn >
249 fiber( std::allocator_arg_t, preallocated, segmented_stack, Fn &&);
250 #endif
251
~fiber()252 ~fiber() {
253 if ( BOOST_UNLIKELY( nullptr != fctx_) ) {
254 detail::ontop_fcontext(
255 #if defined(BOOST_NO_CXX14_STD_EXCHANGE)
256 detail::exchange( fctx_, nullptr),
257 #else
258 std::exchange( fctx_, nullptr),
259 #endif
260 nullptr,
261 detail::fiber_unwind);
262 }
263 }
264
fiber(fiber && other)265 fiber( fiber && other) noexcept {
266 swap( other);
267 }
268
operator =(fiber && other)269 fiber & operator=( fiber && other) noexcept {
270 if ( BOOST_LIKELY( this != & other) ) {
271 fiber tmp = std::move( other);
272 swap( tmp);
273 }
274 return * this;
275 }
276
277 fiber( fiber const& other) noexcept = delete;
278 fiber & operator=( fiber const& other) noexcept = delete;
279
resume()280 fiber resume() && {
281 BOOST_ASSERT( nullptr != fctx_);
282 return { detail::jump_fcontext(
283 #if defined(BOOST_NO_CXX14_STD_EXCHANGE)
284 detail::exchange( fctx_, nullptr),
285 #else
286 std::exchange( fctx_, nullptr),
287 #endif
288 nullptr).fctx };
289 }
290
291 template< typename Fn >
resume_with(Fn && fn)292 fiber resume_with( Fn && fn) && {
293 BOOST_ASSERT( nullptr != fctx_);
294 auto p = std::forward< Fn >( fn);
295 return { detail::ontop_fcontext(
296 #if defined(BOOST_NO_CXX14_STD_EXCHANGE)
297 detail::exchange( fctx_, nullptr),
298 #else
299 std::exchange( fctx_, nullptr),
300 #endif
301 & p,
302 detail::fiber_ontop< fiber, decltype(p) >).fctx };
303 }
304
operator bool() const305 explicit operator bool() const noexcept {
306 return nullptr != fctx_;
307 }
308
operator !() const309 bool operator!() const noexcept {
310 return nullptr == fctx_;
311 }
312
operator <(fiber const & other) const313 bool operator<( fiber const& other) const noexcept {
314 return fctx_ < other.fctx_;
315 }
316
317 #if !defined(BOOST_EMBTC)
318
319 template< typename charT, class traitsT >
320 friend std::basic_ostream< charT, traitsT > &
operator <<(std::basic_ostream<charT,traitsT> & os,fiber const & other)321 operator<<( std::basic_ostream< charT, traitsT > & os, fiber const& other) {
322 if ( nullptr != other.fctx_) {
323 return os << other.fctx_;
324 } else {
325 return os << "{not-a-context}";
326 }
327 }
328
329 #else
330
331 template< typename charT, class traitsT >
332 friend std::basic_ostream< charT, traitsT > &
333 operator<<( std::basic_ostream< charT, traitsT > & os, fiber const& other);
334
335 #endif
336
swap(fiber & other)337 void swap( fiber & other) noexcept {
338 std::swap( fctx_, other.fctx_);
339 }
340 };
341
342 #if defined(BOOST_EMBTC)
343
344 template< typename charT, class traitsT >
345 inline std::basic_ostream< charT, traitsT > &
operator <<(std::basic_ostream<charT,traitsT> & os,fiber const & other)346 operator<<( std::basic_ostream< charT, traitsT > & os, fiber const& other) {
347 if ( nullptr != other.fctx_) {
348 return os << other.fctx_;
349 } else {
350 return os << "{not-a-context}";
351 }
352 }
353
354 #endif
355
356 inline
swap(fiber & l,fiber & r)357 void swap( fiber & l, fiber & r) noexcept {
358 l.swap( r);
359 }
360
361 typedef fiber fiber_context;
362
363 }}
364
365 #if defined(BOOST_MSVC)
366 # pragma warning(pop)
367 #endif
368
369 #ifdef BOOST_HAS_ABI_HEADERS
370 # include BOOST_ABI_SUFFIX
371 #endif
372
373 #endif // BOOST_CONTEXT_FIBER_H
374