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+
+// Copyright Oliver Kowalke 2014.
+// Distributed under the Boost Software License, Version 1.0.
+// (See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_CONTEXT_EXECUTION_CONTEXT_H
+#define BOOST_CONTEXT_EXECUTION_CONTEXT_H
+
+#include <boost/context/detail/config.hpp>
+
+#if ! defined(BOOST_CONTEXT_NO_EXECUTION_CONTEXT)
+
+#include <windows.h>
+
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <memory>
+#include <tuple>
+#include <utility>
+
+#include <boost/assert.hpp>
+#include <boost/config.hpp>
+#include <boost/intrusive_ptr.hpp>
+
+#include <boost/context/detail/invoke.hpp>
+#include <boost/context/stack_context.hpp>
+
+#ifdef BOOST_HAS_ABI_HEADERS
+# include BOOST_ABI_PREFIX
+#endif
+
+namespace boost {
+namespace context {
+
+struct preallocated {
+ void * sp;
+ std::size_t size;
+ stack_context sctx;
+
+ preallocated( void * sp_, std::size_t size_, stack_context sctx_) noexcept :
+ sp( sp_), size( size_), sctx( sctx_) {
+ }
+};
+
+class BOOST_CONTEXT_DECL execution_context {
+private:
+ struct activation_record {
+ typedef boost::intrusive_ptr< activation_record > ptr_t;
+
+ enum flag_t {
+ flag_main_ctx = 1 << 1,
+ flag_preserve_fpu = 1 << 2,
+ flag_segmented_stack = 1 << 3
+ };
+
+ thread_local static activation_record toplevel_rec;
+ thread_local static ptr_t current_rec;
+
+ std::size_t use_count;
+ LPVOID fiber;
+ stack_context sctx;
+ int flags;
+
+ // used for toplevel-context
+ // (e.g. main context, thread-entry context)
+ activation_record() noexcept :
+ use_count( 1),
+ fiber( nullptr),
+ sctx(),
+ flags( flag_main_ctx) {
+ }
+
+ activation_record( stack_context sctx_, bool use_segmented_stack) noexcept :
+ use_count( 0),
+ fiber( nullptr),
+ sctx( sctx_),
+ flags( use_segmented_stack ? flag_segmented_stack : 0) {
+ }
+
+ virtual ~activation_record() noexcept = default;
+
+ void resume() noexcept {
+ // store current activation record in local variable
+ activation_record * from = current_rec.get();
+ // store `this` in static, thread local pointer
+ // `this` will become the active (running) context
+ // returned by execution_context::current()
+ current_rec = this;
+ // context switch from parent context to `this`-context
+#if ( _WIN32_WINNT > 0x0600)
+ if ( ::IsThreadAFiber() ) {
+ from->fiber = ::GetCurrentFiber();
+ } else {
+ from->fiber = ::ConvertThreadToFiber( nullptr);
+ }
+#else
+ from->fiber = ::ConvertThreadToFiber( nullptr);
+ if ( nullptr == from->fiber) {
+ DWORD err = ::GetLastError();
+ BOOST_ASSERT( ERROR_ALREADY_FIBER == err);
+ from->fiber = ::GetCurrentFiber();
+ BOOST_ASSERT( nullptr != from->fiber);
+ BOOST_ASSERT( reinterpret_cast< LPVOID >( 0x1E00) != from->fiber);
+ }
+#endif
+ ::SwitchToFiber( fiber);
+ }
+
+ virtual void deallocate() {}
+
+ friend void intrusive_ptr_add_ref( activation_record * ar) {
+ ++ar->use_count;
+ }
+
+ friend void intrusive_ptr_release( activation_record * ar) {
+ BOOST_ASSERT( nullptr != ar);
+
+ if ( 0 == --ar->use_count) {
+ ar->deallocate();
+ }
+ }
+ };
+
+ template< typename Fn, typename StackAlloc >
+ class capture_record : public activation_record {
+ private:
+ StackAlloc salloc_;
+ Fn fn_;
+
+ static void destroy( capture_record * p) {
+ StackAlloc salloc( p->salloc_);
+ stack_context sctx( p->sctx);
+ // deallocate activation record
+ p->~capture_record();
+ // destroy stack with stack allocator
+ salloc.deallocate( sctx);
+ }
+
+ public:
+ explicit capture_record( stack_context sctx, StackAlloc const& salloc, Fn && fn, bool use_segmented_stack) noexcept :
+ activation_record( sctx, use_segmented_stack),
+ salloc_( salloc),
+ fn_( std::forward< Fn >( fn) ) {
+ }
+
+ void deallocate() override final {
+ destroy( this);
+ }
+
+ void run() noexcept {
+ try {
+ fn_();
+ } catch (...) {
+ std::terminate();
+ }
+ BOOST_ASSERT( 0 == (flags & flag_main_ctx) );
+ }
+ };
+
+ // tampoline function
+ // entered if the execution context
+ // is resumed for the first time
+ template< typename AR >
+ static VOID WINAPI entry_func( LPVOID p) {
+ BOOST_ASSERT( 0 != p);
+
+ AR * ar( reinterpret_cast< AR * >( p) );
+ // start execution of toplevel context-function
+ ar->run();
+ //ctx->fn_(ctx->param_);
+ ::DeleteFiber( ar->fiber);
+ }
+
+ typedef boost::intrusive_ptr< activation_record > ptr_t;
+
+ ptr_t ptr_;
+
+ template< typename StackAlloc, typename Fn >
+ static activation_record * create_context( StackAlloc salloc, Fn && fn, bool use_segmented_stack) {
+ typedef capture_record< Fn, StackAlloc > capture_t;
+
+ // hackish
+ std::size_t fsize = salloc.size_;
+ salloc.size_ = sizeof( capture_t);
+
+ stack_context sctx( salloc.allocate() );
+ // reserve space for control structure
+ void * sp = static_cast< char * >( sctx.sp) - sizeof( capture_t);
+ // placment new for control structure on fast-context stack
+ capture_t * cr = new ( sp) capture_t( sctx, salloc, std::forward< Fn >( fn), use_segmented_stack);
+ // create fiber
+ // use default stacksize
+ cr->fiber = ::CreateFiber( fsize, execution_context::entry_func< capture_t >, cr);
+ BOOST_ASSERT( nullptr != cr->fiber);
+ return cr;
+ }
+
+ template< typename StackAlloc, typename Fn >
+ static activation_record * create_context( preallocated palloc, StackAlloc salloc, Fn && fn, bool use_segmented_stack) {
+ typedef capture_record< Fn, StackAlloc > capture_t;
+
+ // hackish
+ std::size_t fsize = salloc.size_;
+ salloc.size_ = sizeof( capture_t);
+
+ // reserve space for control structure
+ void * sp = static_cast< char * >( palloc.sp) - sizeof( capture_t);
+ // placment new for control structure on fast-context stack
+ capture_t * cr = new ( sp) capture_t( palloc.sctx, salloc, std::forward< Fn >( fn), use_segmented_stack);
+ // create fiber
+ // use default stacksize
+ cr->fiber = ::CreateFiber( fsize, execution_context::entry_func< capture_t >, cr);
+ BOOST_ASSERT( nullptr != cr->fiber);
+ return cr;
+ }
+
+ template< typename StackAlloc, typename Fn, typename Tpl, std::size_t ... I >
+ static activation_record * create_capture_record( StackAlloc salloc,
+ Fn && fn_, Tpl && tpl_,
+ std::index_sequence< I ... >,
+ bool use_segmented_stack) {
+ return create_context(
+ salloc,
+ // lambda, executed in new execution context
+ [fn=std::forward< Fn >( fn_),tpl=std::forward< Tpl >( tpl_)] () mutable -> decltype( auto) {
+ detail::invoke( fn,
+ // non-type template parameter pack used to extract the
+ // parameters (arguments) from the tuple and pass them to fn
+ // via parameter pack expansion
+ // std::tuple_element<> does not perfect forwarding
+ std::forward< decltype( std::get< I >( std::declval< Tpl >() ) ) >(
+ std::get< I >( std::forward< Tpl >( tpl) ) ) ... );
+ },
+ use_segmented_stack);
+ }
+
+ template< typename StackAlloc, typename Fn, typename Tpl, std::size_t ... I >
+ static activation_record * create_capture_record( preallocated palloc, StackAlloc salloc,
+ Fn && fn_, Tpl && tpl_,
+ std::index_sequence< I ... >,
+ bool use_segmented_stack) {
+ return create_context(
+ palloc, salloc,
+ // lambda, executed in new execution context
+ [fn=std::forward< Fn >( fn_),tpl=std::forward< Tpl >( tpl_)] () mutable -> decltype( auto) {
+ detail::invoke( fn,
+ // non-type template parameter pack used to extract the
+ // parameters (arguments) from the tuple and pass them to fn
+ // via parameter pack expansion
+ // std::tuple_element<> does not perfect forwarding
+ std::forward< decltype( std::get< I >( std::declval< Tpl >() ) ) >(
+ std::get< I >( std::forward< Tpl >( tpl) ) ) ... );
+ },
+ use_segmented_stack);
+ }
+
+ execution_context() :
+ // default constructed with current activation_record
+ ptr_( activation_record::current_rec) {
+ }
+
+public:
+ static execution_context current() noexcept {
+ return execution_context();
+ }
+
+ template< typename StackAlloc, typename Fn, typename ... Args >
+ explicit execution_context( StackAlloc salloc, Fn && fn, Args && ... args) :
+ // deferred execution of fn and its arguments
+ // arguments are stored in std::tuple<>
+ // non-type template parameter pack via std::index_sequence_for<>
+ // preserves the number of arguments
+ // used to extract the function arguments from std::tuple<>
+ ptr_( create_capture_record( salloc,
+ std::forward< Fn >( fn),
+ std::make_tuple( std::forward< Args >( args) ... ),
+ std::index_sequence_for< Args ... >(), false) ) {
+ }
+
+ template< typename StackAlloc, typename Fn, typename ... Args >
+ explicit execution_context( preallocated palloc, StackAlloc salloc, Fn && fn, Args && ... args) :
+ // deferred execution of fn and its arguments
+ // arguments are stored in std::tuple<>
+ // non-type template parameter pack via std::index_sequence_for<>
+ // preserves the number of arguments
+ // used to extract the function arguments from std::tuple<>
+ ptr_( create_capture_record( palloc, salloc,
+ std::forward< Fn >( fn),
+ std::make_tuple( std::forward< Args >( args) ... ),
+ std::index_sequence_for< Args ... >(), false) ) {
+ }
+
+ void operator()( bool preserve_fpu = false) noexcept {
+ ptr_->resume();
+ }
+};
+
+}}
+
+# ifdef BOOST_HAS_ABI_HEADERS
+# include BOOST_ABI_SUFFIX
+# endif
+
+#endif
+
+#endif // BOOST_CONTEXT_EXECUTION_CONTEXT_H
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