ceph/src/boost/boost/context/execution_context_v2.hpp

   1
   2 //          Copyright Oliver Kowalke 2014.
   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_EXECUTION_CONTEXT_H
   8 #define BOOST_CONTEXT_EXECUTION_CONTEXT_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_CXX17_STD_APPLY)
  28 #include <boost/context/detail/apply.hpp>
  29 #endif
  30 #include <boost/context/detail/disable_overload.hpp>
  31 #include <boost/context/detail/exception.hpp>
  32 #include <boost/context/detail/exchange.hpp>
  33 #include <boost/context/detail/fcontext.hpp>
  34 #include <boost/context/detail/tuple.hpp>
  35 #include <boost/context/fixedsize_stack.hpp>
  36 #include <boost/context/flags.hpp>
  37 #include <boost/context/preallocated.hpp>
  38 #include <boost/context/segmented_stack.hpp>
  39 #include <boost/context/stack_context.hpp>
  40
  41 #ifdef BOOST_HAS_ABI_HEADERS
  42 # include BOOST_ABI_PREFIX
  43 #endif
  44
  45 #if defined(BOOST_MSVC)
  46 # pragma warning(push)
  47 # pragma warning(disable: 4702)
  48 #endif
  49
  50 namespace boost {
  51 namespace context {
  52 namespace detail {
  53
  54 transfer_t context_unwind( transfer_t);
  55
  56 template< typename Rec >
  57 transfer_t context_exit( transfer_t) noexcept;
  58
  59 template< typename Rec >
  60 void context_entry( transfer_t) noexcept;
  61
  62 template< typename Ctx, typename Fn, typename ... Args >
  63 transfer_t context_ontop( transfer_t);
  64
  65 template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
  66 fcontext_t context_create( StackAlloc &&, Fn &&, Params && ...);
  67
  68 template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
  69 fcontext_t context_create( preallocated, StackAlloc &&, Fn &&, Params && ...);
  70
  71 template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
  72 class record {
  73 private:
  74     typename std::decay< StackAlloc >::type             salloc_;
  75     stack_context                                       sctx_;
  76     typename std::decay< Fn >::type                     fn_;
  77     std::tuple< typename std::decay< Params >::type ... > params_;
  78
  79     static void destroy( record * p) noexcept {
  80         typename std::decay< StackAlloc >::type salloc = std::move( p->salloc_);
  81         stack_context sctx = p->sctx_;
  82         // deallocate record
  83         p->~record();
  84         // destroy stack with stack allocator
  85         salloc.deallocate( sctx);
  86     }
  87
  88 public:
  89     record( stack_context sctx, StackAlloc && salloc,
  90             Fn && fn, Params && ... params) noexcept :
  91         salloc_( std::forward< StackAlloc >( salloc)),
  92         sctx_( sctx),
  93         fn_( std::forward< Fn >( fn) ),
  94         params_( std::forward< Params >( params) ... ) {
  95     }
  96
  97     record( record const&) = delete;
  98     record & operator=( record const&) = delete;
  99
 100     void deallocate() noexcept {
 101         destroy( this);
 102     }
 103
 104     transfer_t run( transfer_t t) {
 105         Ctx from{ t.fctx };
 106         typename Ctx::args_tpl_t args = std::move( std::get<1>( * static_cast< std::tuple< std::exception_ptr, typename Ctx::args_tpl_t > * >( t.data) ) );
 107         auto tpl = std::tuple_cat(
 108                     params_,
 109                     std::forward_as_tuple( std::move( from) ),
 110                     std::move( args) );
 111         // invoke context-function
 112 #if defined(BOOST_NO_CXX17_STD_APPLY)
 113         Ctx cc = apply( std::move( fn_), std::move( tpl) );
 114 #else
 115         Ctx cc = std::apply( std::move( fn_), std::move( tpl) );
 116 #endif
 117         return { exchange( cc.fctx_, nullptr), nullptr };
 118     }
 119 };
 120
 121 }
 122
 123 template< typename ... Args >
 124 class execution_context {
 125 private:
 126     friend class ontop_error;
 127
 128     typedef std::tuple< Args ... >     args_tpl_t;
 129     typedef std::tuple< execution_context, typename std::decay< Args >::type ... >               ret_tpl_t;
 130
 131     template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
 132     friend class detail::record;
 133
 134     template< typename Ctx, typename Fn, typename ... ArgsT >
 135     friend detail::transfer_t detail::context_ontop( detail::transfer_t);
 136
 137     detail::fcontext_t  fctx_{ nullptr };
 138
 139     execution_context( detail::fcontext_t fctx) noexcept :
 140         fctx_( fctx) {
 141     }
 142
 143 public:
 144     execution_context() noexcept = default;
 145
 146 #if defined(BOOST_USE_SEGMENTED_STACKS)
 147     // segmented-stack requires to preserve the segments of the `current` context
 148     // which is not possible (no global pointer to current context)
 149     template< typename Fn, typename ... Params >
 150     execution_context( std::allocator_arg_t, segmented_stack, Fn &&, Params && ...) = delete;
 151
 152     template< typename Fn, typename ... Params >
 153     execution_context( std::allocator_arg_t, preallocated, segmented_stack, Fn &&, Params && ...) = delete;
 154 #else
 155     template< typename Fn,
 156               typename ... Params,
 157               typename = detail::disable_overload< execution_context, Fn >
 158     >
 159     execution_context( Fn && fn, Params && ... params) :
 160         // deferred execution of fn and its arguments
 161         // arguments are stored in std::tuple<>
 162         // non-type template parameter pack via std::index_sequence_for<>
 163         // preserves the number of arguments
 164         // used to extract the function arguments from std::tuple<>
 165         fctx_( detail::context_create< execution_context >(
 166                     fixedsize_stack(),
 167                     std::forward< Fn >( fn),
 168                     std::forward< Params >( params) ... ) ) {
 169     }
 170
 171     template< typename StackAlloc,
 172               typename Fn,
 173               typename ... Params
 174     >
 175     execution_context( std::allocator_arg_t, StackAlloc && salloc, Fn && fn, Params && ... params) :
 176         // deferred execution of fn and its arguments
 177         // arguments are stored in std::tuple<>
 178         // non-type template parameter pack via std::index_sequence_for<>
 179         // preserves the number of arguments
 180         // used to extract the function arguments from std::tuple<>
 181         fctx_( detail::context_create< execution_context >(
 182                     std::forward< StackAlloc >( salloc),
 183                     std::forward< Fn >( fn),
 184                     std::forward< Params >( params) ... ) ) {
 185     }
 186
 187     template< typename StackAlloc,
 188               typename Fn,
 189               typename ... Params
 190     >
 191     execution_context( std::allocator_arg_t, preallocated palloc, StackAlloc && salloc, Fn && fn, Params && ... params) :
 192         // deferred execution of fn and its arguments
 193         // arguments are stored in std::tuple<>
 194         // non-type template parameter pack via std::index_sequence_for<>
 195         // preserves the number of arguments
 196         // used to extract the function arguments from std::tuple<>
 197         fctx_( detail::context_create< execution_context >(
 198                     palloc, std::forward< StackAlloc >( salloc),
 199                     std::forward< Fn >( fn),
 200                     std::forward< Params >( params) ... ) ) {
 201     }
 202 #endif
 203
 204     ~execution_context() {
 205         if ( nullptr != fctx_) {
 206             detail::ontop_fcontext( detail::exchange( fctx_, nullptr), nullptr, detail::context_unwind);
 207         }
 208     }
 209
 210     execution_context( execution_context && other) noexcept :
 211         fctx_( other.fctx_) {
 212         other.fctx_ = nullptr;
 213     }
 214
 215     execution_context & operator=( execution_context && other) noexcept {
 216         if ( this != & other) {
 217             execution_context tmp = std::move( other);
 218             swap( tmp);
 219         }
 220         return * this;
 221     }
 222
 223     execution_context( execution_context const& other) noexcept = delete;
 224     execution_context & operator=( execution_context const& other) noexcept = delete;
 225
 226     ret_tpl_t operator()( Args ... args);
 227
 228     template< typename Fn >
 229     ret_tpl_t operator()( exec_ontop_arg_t, Fn && fn, Args ... args);
 230
 231     explicit operator bool() const noexcept {
 232         return nullptr != fctx_;
 233     }
 234
 235     bool operator!() const noexcept {
 236         return nullptr == fctx_;
 237     }
 238
 239     bool operator==( execution_context const& other) const noexcept {
 240         return fctx_ == other.fctx_;
 241     }
 242
 243     bool operator!=( execution_context const& other) const noexcept {
 244         return fctx_ != other.fctx_;
 245     }
 246
 247     bool operator<( execution_context const& other) const noexcept {
 248         return fctx_ < other.fctx_;
 249     }
 250
 251     bool operator>( execution_context const& other) const noexcept {
 252         return other.fctx_ < fctx_;
 253     }
 254
 255     bool operator<=( execution_context const& other) const noexcept {
 256         return ! ( * this > other);
 257     }
 258
 259     bool operator>=( execution_context const& other) const noexcept {
 260         return ! ( * this < other);
 261     }
 262
 263     template< typename charT, class traitsT >
 264     friend std::basic_ostream< charT, traitsT > &
 265     operator<<( std::basic_ostream< charT, traitsT > & os, execution_context const& other) {
 266         if ( nullptr != other.fctx_) {
 267             return os << other.fctx_;
 268         } else {
 269             return os << "{not-a-context}";
 270         }
 271     }
 272
 273     void swap( execution_context & other) noexcept {
 274         std::swap( fctx_, other.fctx_);
 275     }
 276 };
 277
 278 class ontop_error : public std::exception {
 279 private:
 280     detail::fcontext_t  fctx_;
 281
 282 public:
 283     ontop_error( detail::fcontext_t fctx) noexcept :
 284         fctx_{ fctx } {
 285     }
 286
 287     template< typename ... Args >
 288     execution_context< Args ... > get_context() const noexcept {
 289         return execution_context< Args ... >{ fctx_ };
 290     }
 291 };
 292
 293 template< typename ... Args >
 294 typename execution_context< Args ... >::ret_tpl_t
 295 execution_context< Args ... >::operator()( Args ... args) {
 296     BOOST_ASSERT( nullptr != fctx_);
 297     args_tpl_t data( std::forward< Args >( args) ... );
 298     auto p = std::make_tuple( std::exception_ptr{}, std::move( data) );
 299     detail::transfer_t t = detail::jump_fcontext( detail::exchange( fctx_, nullptr), & p);
 300     if ( nullptr != t.data) {
 301         auto p = static_cast< std::tuple< std::exception_ptr, args_tpl_t > * >( t.data);
 302         std::exception_ptr eptr = std::get< 0 >( * p);
 303         if ( eptr) {
 304             try {
 305                 std::rethrow_exception( eptr);
 306             } catch (...) {
 307                 std::throw_with_nested( ontop_error{ t.fctx } );
 308             }
 309         }
 310         data = std::move( std::get< 1 >( * p) );
 311     }
 312     return std::tuple_cat( std::forward_as_tuple( execution_context( t.fctx) ), std::move( data) );
 313 }
 314
 315 template< typename ... Args >
 316 template< typename Fn >
 317 typename execution_context< Args ... >::ret_tpl_t
 318 execution_context< Args ... >::operator()( exec_ontop_arg_t, Fn && fn, Args ... args) {
 319     BOOST_ASSERT( nullptr != fctx_);
 320     args_tpl_t data{ std::forward< Args >( args) ... };
 321     auto p = std::make_tuple( fn, std::make_tuple( std::exception_ptr{}, std::move( data) ) );
 322     detail::transfer_t t = detail::ontop_fcontext(
 323             detail::exchange( fctx_, nullptr),
 324             & p,
 325             detail::context_ontop< execution_context, Fn, Args ... >);
 326     if ( nullptr != t.data) {
 327         auto p = static_cast< std::tuple< std::exception_ptr, args_tpl_t > * >( t.data);
 328         std::exception_ptr eptr = std::get< 0 >( * p);
 329         if ( eptr) {
 330             try {
 331                 std::rethrow_exception( eptr);
 332             } catch (...) {
 333                 std::throw_with_nested( ontop_error{ t.fctx } );
 334             }
 335         }
 336         data = std::move( std::get< 1 >( * p) );
 337     }
 338     return std::tuple_cat( std::forward_as_tuple( execution_context( t.fctx) ), std::move( data) );
 339 }
 340
 341 namespace detail {
 342
 343 template< int N >
 344 struct helper {
 345     template< typename T >
 346     static T convert( T && t) noexcept {
 347         return std::forward< T >( t);
 348     }
 349 };
 350
 351 template<>
 352 struct helper< 1 > {
 353     template< typename T >
 354     static std::tuple< T > convert( T && t) noexcept {
 355         return std::make_tuple( std::forward< T >( t) );
 356     }
 357 };
 358
 359 inline
 360 transfer_t context_unwind( transfer_t t) {
 361     throw forced_unwind( t.fctx);
 362     return { nullptr, nullptr };
 363 }
 364
 365 template< typename Rec >
 366 transfer_t context_exit( transfer_t t) noexcept {
 367     Rec * rec = static_cast< Rec * >( t.data);
 368     // destroy context stack
 369     rec->deallocate();
 370     return { nullptr, nullptr };
 371 }
 372
 373 template< typename Rec >
 374 void context_entry( transfer_t t_) noexcept {
 375     // transfer control structure to the context-stack
 376     Rec * rec = static_cast< Rec * >( t_.data);
 377     BOOST_ASSERT( nullptr != rec);
 378     transfer_t t = { nullptr, nullptr };
 379     try {
 380         // jump back to `context_create()`
 381         t = jump_fcontext( t_.fctx, nullptr);
 382         // start executing
 383         t = rec->run( t);
 384     } catch ( forced_unwind const& e) {
 385         t = { e.fctx, nullptr };
 386     }
 387     BOOST_ASSERT( nullptr != t.fctx);
 388     // destroy context-stack of `this`context on next context
 389     ontop_fcontext( t.fctx, rec, context_exit< Rec >);
 390     BOOST_ASSERT_MSG( false, "context already terminated");
 391 }
 392
 393 template< typename Ctx, typename Fn, typename ... Args >
 394 transfer_t context_ontop( transfer_t t) {
 395     auto p = static_cast< std::tuple< Fn, std::tuple< std::exception_ptr, std::tuple< Args ... > > > * >( t.data);
 396     BOOST_ASSERT( nullptr != p);
 397     typename std::decay< Fn >::type fn = std::forward< Fn >( std::get< 0 >( * p) );
 398     auto args = std::move( std::get< 1 >( std::get< 1 >( * p) ) );
 399     try {
 400         // execute function
 401 #if defined(BOOST_NO_CXX17_STD_APPLY)
 402         std::get< 1 >( std::get< 1 >( * p) ) = helper< sizeof ... (Args) >::convert( apply( fn, std::move( args) ) );
 403 #else
 404         std::get< 1 >( std::get< 1 >( * p) ) = helper< sizeof ... (Args) >::convert( std::apply( fn, std::move( args) ) );
 405 #endif
 406     } catch (...) {
 407         std::get< 0 >( std::get< 1 >( * p) ) = std::current_exception();
 408     }
 409     // apply returned data
 410     return { t.fctx, & std::get< 1 >( * p) };
 411 }
 412
 413 template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
 414 fcontext_t context_create( StackAlloc && salloc, Fn && fn, Params && ... params) {
 415     typedef record< Ctx, StackAlloc, Fn, Params ... >  record_t;
 416
 417     auto sctx = salloc.allocate();
 418     // reserve space for control structure
 419 #if defined(BOOST_NO_CXX11_CONSTEXPR) || defined(BOOST_NO_CXX11_STD_ALIGN)
 420     const std::size_t size = sctx.size - sizeof( record_t);
 421     void * sp = static_cast< char * >( sctx.sp) - sizeof( record_t);
 422 #else
 423     constexpr std::size_t func_alignment = 64; // alignof( record_t);
 424     constexpr std::size_t func_size = sizeof( record_t);
 425     // reserve space on stack
 426     void * sp = static_cast< char * >( sctx.sp) - func_size - func_alignment;
 427     // align sp pointer
 428     std::size_t space = func_size + func_alignment;
 429     sp = std::align( func_alignment, func_size, sp, space);
 430     BOOST_ASSERT( nullptr != sp);
 431     // calculate remaining size
 432     const std::size_t size = sctx.size - ( static_cast< char * >( sctx.sp) - static_cast< char * >( sp) );
 433 #endif
 434     // create fast-context
 435     const fcontext_t fctx = make_fcontext( sp, size, & context_entry< record_t >);
 436     BOOST_ASSERT( nullptr != fctx);
 437     // placment new for control structure on context-stack
 438     auto rec = ::new ( sp) record_t{
 439             sctx, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn), std::forward< Params >( params) ... };
 440     // transfer control structure to context-stack
 441     return jump_fcontext( fctx, rec).fctx;
 442 }
 443
 444 template< typename Ctx, typename StackAlloc, typename Fn, typename ... Params >
 445 fcontext_t context_create( preallocated palloc, StackAlloc && salloc, Fn && fn, Params && ... params) {
 446     typedef record< Ctx, StackAlloc, Fn, Params ... >  record_t;
 447
 448     // reserve space for control structure
 449 #if defined(BOOST_NO_CXX11_CONSTEXPR) || defined(BOOST_NO_CXX11_STD_ALIGN)
 450     const std::size_t size = palloc.size - sizeof( record_t);
 451     void * sp = static_cast< char * >( palloc.sp) - sizeof( record_t);
 452 #else
 453     constexpr std::size_t func_alignment = 64; // alignof( record_t);
 454     constexpr std::size_t func_size = sizeof( record_t);
 455     // reserve space on stack
 456     void * sp = static_cast< char * >( palloc.sp) - func_size - func_alignment;
 457     // align sp pointer
 458     std::size_t space = func_size + func_alignment;
 459     sp = std::align( func_alignment, func_size, sp, space);
 460     BOOST_ASSERT( nullptr != sp);
 461     // calculate remaining size
 462     const std::size_t size = palloc.size - ( static_cast< char * >( palloc.sp) - static_cast< char * >( sp) );
 463 #endif
 464     // create fast-context
 465     const fcontext_t fctx = make_fcontext( sp, size, & context_entry< record_t >);
 466     BOOST_ASSERT( nullptr != fctx);
 467     // placment new for control structure on context-stack
 468     auto rec = ::new ( sp) record_t{
 469             palloc.sctx, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn), std::forward< Params >( params) ... };
 470     // transfer control structure to context-stack
 471     return jump_fcontext( fctx, rec).fctx;
 472 }
 473
 474 }
 475
 476 #include <boost/context/execution_context_v2_void.ipp>
 477
 478 template< typename ... Args >
 479 void swap( execution_context< Args ... > & l, execution_context< Args ... > & r) noexcept {
 480     l.swap( r);
 481 }
 482
 483 }}
 484
 485 #if defined(BOOST_MSVC)
 486 # pragma warning(pop)
 487 #endif
 488
 489 #ifdef BOOST_HAS_ABI_HEADERS
 490 # include BOOST_ABI_SUFFIX
 491 #endif
 492
 493 #endif // BOOST_CONTEXT_EXECUTION_CONTEXT_H