mirror of
https://github.com/ecency/ecency-mobile.git
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498 lines
18 KiB
C++
498 lines
18 KiB
C++
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// Copyright Oliver Kowalke 2014.
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_CONTEXT_EXECUTION_CONTEXT_H
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#define BOOST_CONTEXT_EXECUTION_CONTEXT_H
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#include <boost/context/detail/config.hpp>
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#include <algorithm>
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#include <atomic>
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#include <cstddef>
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#include <cstdint>
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#include <cstdlib>
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#include <functional>
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#include <memory>
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#include <ostream>
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#include <tuple>
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#include <utility>
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#include <boost/assert.hpp>
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#include <boost/config.hpp>
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#include <boost/intrusive_ptr.hpp>
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#if defined(BOOST_NO_CXX17_STD_APPLY)
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#include <boost/context/detail/apply.hpp>
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#endif
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#include <boost/context/detail/disable_overload.hpp>
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#include <boost/context/detail/fcontext.hpp>
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#include <boost/context/fixedsize_stack.hpp>
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#include <boost/context/flags.hpp>
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#include <boost/context/preallocated.hpp>
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#include <boost/context/segmented_stack.hpp>
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#include <boost/context/stack_context.hpp>
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#ifdef BOOST_HAS_ABI_HEADERS
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# include BOOST_ABI_PREFIX
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#endif
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#if defined(BOOST_USE_SEGMENTED_STACKS)
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extern "C" {
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void __splitstack_getcontext( void * [BOOST_CONTEXT_SEGMENTS]);
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void __splitstack_setcontext( void * [BOOST_CONTEXT_SEGMENTS]);
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}
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#endif
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namespace boost {
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namespace context {
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namespace detail {
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template< typename Fn >
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transfer_t context_ontop( transfer_t);
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struct activation_record;
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struct data_t {
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activation_record * from;
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void * data;
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};
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struct activation_record {
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typedef boost::intrusive_ptr< activation_record > ptr_t;
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thread_local static ptr_t current_rec;
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std::atomic< std::size_t > use_count{ 0 };
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fcontext_t fctx{ nullptr };
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stack_context sctx{};
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bool main_ctx{ true };
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// used for toplevel-context
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// (e.g. main context, thread-entry context)
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constexpr activation_record() = default;
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activation_record( fcontext_t fctx_, stack_context sctx_) noexcept :
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fctx{ fctx_ },
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sctx( sctx_ ), // sctx{ sctx_ } - clang-3.6: no viable conversion from 'boost::context::stack_context' to 'std::size_t'
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main_ctx{ false } {
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}
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virtual ~activation_record() = default;
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bool is_main_context() const noexcept {
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return main_ctx;
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}
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void * resume( void * vp) {
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// store current activation record in local variable
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auto from = current_rec.get();
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// store `this` in static, thread local pointer
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// `this` will become the active (running) context
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// returned by execution_context::current()
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current_rec = this;
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#if defined(BOOST_USE_SEGMENTED_STACKS)
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// adjust segmented stack properties
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__splitstack_getcontext( from->sctx.segments_ctx);
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__splitstack_setcontext( sctx.segments_ctx);
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#endif
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data_t d = { from, vp };
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// context switch from parent context to `this`-context
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transfer_t t = jump_fcontext( fctx, & d);
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data_t * dp = reinterpret_cast< data_t * >( t.data);
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dp->from->fctx = t.fctx;
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// parent context resumed
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return dp->data;
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}
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template< typename Fn >
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void * resume_ontop( void * data, Fn && fn) {
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// store current activation record in local variable
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activation_record * from = current_rec.get();
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// store `this` in static, thread local pointer
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// `this` will become the active (running) context
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// returned by execution_context::current()
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current_rec = this;
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#if defined(BOOST_USE_SEGMENTED_STACKS)
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// adjust segmented stack properties
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__splitstack_getcontext( from->sctx.segments_ctx);
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__splitstack_setcontext( sctx.segments_ctx);
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#endif
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std::tuple< void *, Fn > p = std::forward_as_tuple( data, fn);
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data_t d = { from, & p };
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// context switch from parent context to `this`-context
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// execute Fn( Tpl) on top of `this`
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transfer_t t = ontop_fcontext( fctx, & d, context_ontop< Fn >);
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data_t * dp = reinterpret_cast< data_t * >( t.data);
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dp->from->fctx = t.fctx;
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// parent context resumed
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return dp->data;
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}
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virtual void deallocate() noexcept {
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}
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friend void intrusive_ptr_add_ref( activation_record * ar) noexcept {
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++ar->use_count;
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}
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friend void intrusive_ptr_release( activation_record * ar) noexcept {
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BOOST_ASSERT( nullptr != ar);
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if ( 0 == --ar->use_count) {
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ar->deallocate();
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}
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}
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};
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struct activation_record_initializer {
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activation_record_initializer() noexcept;
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~activation_record_initializer();
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};
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template< typename Fn >
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transfer_t context_ontop( transfer_t t) {
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data_t * dp = reinterpret_cast< data_t * >( t.data);
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dp->from->fctx = t.fctx;
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auto tpl = reinterpret_cast< std::tuple< void *, Fn > * >( dp->data);
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BOOST_ASSERT( nullptr != tpl);
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auto data = std::get< 0 >( * tpl);
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typename std::decay< Fn >::type fn = std::forward< Fn >( std::get< 1 >( * tpl) );
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#if defined(BOOST_NO_CXX17_STD_APPLY)
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dp->data = apply( fn, std::tie( data) );
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#else
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dp->data = std::apply( fn, std::tie( data) );
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#endif
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return { t.fctx, dp };
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}
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template< typename StackAlloc, typename Fn, typename ... Args >
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class capture_record : public activation_record {
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private:
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StackAlloc salloc_;
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typename std::decay< Fn >::type fn_;
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std::tuple< typename std::decay< Args >::type ... > args_;
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activation_record * caller_;
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static void destroy( capture_record * p) noexcept {
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StackAlloc salloc = p->salloc_;
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stack_context sctx = p->sctx;
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// deallocate activation record
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p->~capture_record();
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// destroy stack with stack allocator
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salloc.deallocate( sctx);
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}
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public:
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capture_record( stack_context sctx, StackAlloc const& salloc,
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fcontext_t fctx,
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activation_record * caller,
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Fn && fn, Args && ... args) noexcept :
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activation_record{ fctx, sctx },
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salloc_{ salloc },
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fn_( std::forward< Fn >( fn) ),
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args_( std::forward< Args >( args) ... ),
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caller_{ caller } {
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}
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void deallocate() noexcept override final {
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destroy( this);
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}
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void run() {
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auto data = caller_->resume( nullptr);
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#if defined(BOOST_NO_CXX17_STD_APPLY)
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apply( fn_, std::tuple_cat( args_, std::tie( data) ) );
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#else
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std::apply( fn_, std::tuple_cat( args_, std::tie( data) ) );
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#endif
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BOOST_ASSERT_MSG( ! main_ctx, "main-context does not execute activation-record::run()");
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}
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};
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}
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class BOOST_CONTEXT_DECL execution_context {
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private:
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// tampoline function
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// entered if the execution context
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// is resumed for the first time
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template< typename AR >
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static void entry_func( detail::transfer_t t) noexcept {
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detail::data_t * dp = reinterpret_cast< detail::data_t * >( t.data);
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AR * ar = static_cast< AR * >( dp->data);
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BOOST_ASSERT( nullptr != ar);
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dp->from->fctx = t.fctx;
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// start execution of toplevel context-function
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ar->run();
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}
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typedef boost::intrusive_ptr< detail::activation_record > ptr_t;
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ptr_t ptr_;
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template< typename StackAlloc, typename Fn, typename ... Args >
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static detail::activation_record * create_context( StackAlloc salloc,
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Fn && fn, Args && ... args) {
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typedef detail::capture_record<
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StackAlloc, Fn, Args ...
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> capture_t;
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auto sctx = salloc.allocate();
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// reserve space for control structure
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#if defined(BOOST_NO_CXX11_CONSTEXPR) || defined(BOOST_NO_CXX11_STD_ALIGN)
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const std::size_t size = sctx.size - sizeof( capture_t);
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void * sp = static_cast< char * >( sctx.sp) - sizeof( capture_t);
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#else
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constexpr std::size_t func_alignment = 64; // alignof( capture_t);
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constexpr std::size_t func_size = sizeof( capture_t);
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// reserve space on stack
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void * sp = static_cast< char * >( sctx.sp) - func_size - func_alignment;
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// align sp pointer
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std::size_t space = func_size + func_alignment;
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sp = std::align( func_alignment, func_size, sp, space);
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BOOST_ASSERT( nullptr != sp);
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// calculate remaining size
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const std::size_t size = sctx.size - ( static_cast< char * >( sctx.sp) - static_cast< char * >( sp) );
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#endif
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// create fast-context
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const detail::fcontext_t fctx = detail::make_fcontext( sp, size, & execution_context::entry_func< capture_t >);
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BOOST_ASSERT( nullptr != fctx);
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// get current activation record
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auto curr = execution_context::current().ptr_;
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// placment new for control structure on fast-context stack
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return ::new ( sp) capture_t{
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sctx, salloc, fctx, curr.get(), std::forward< Fn >( fn), std::forward< Args >( args) ... };
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}
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template< typename StackAlloc, typename Fn, typename ... Args >
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static detail::activation_record * create_context( preallocated palloc, StackAlloc salloc,
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Fn && fn, Args && ... args) {
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typedef detail::capture_record<
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StackAlloc, Fn, Args ...
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> capture_t;
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// reserve space for control structure
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#if defined(BOOST_NO_CXX11_CONSTEXPR) || defined(BOOST_NO_CXX11_STD_ALIGN)
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const std::size_t size = palloc.size - sizeof( capture_t);
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void * sp = static_cast< char * >( palloc.sp) - sizeof( capture_t);
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#else
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constexpr std::size_t func_alignment = 64; // alignof( capture_t);
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constexpr std::size_t func_size = sizeof( capture_t);
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// reserve space on stack
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void * sp = static_cast< char * >( palloc.sp) - func_size - func_alignment;
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// align sp pointer
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std::size_t space = func_size + func_alignment;
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sp = std::align( func_alignment, func_size, sp, space);
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BOOST_ASSERT( nullptr != sp);
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// calculate remaining size
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const std::size_t size = palloc.size - ( static_cast< char * >( palloc.sp) - static_cast< char * >( sp) );
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#endif
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// create fast-context
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const detail::fcontext_t fctx = detail::make_fcontext( sp, size, & execution_context::entry_func< capture_t >);
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BOOST_ASSERT( nullptr != fctx);
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// get current activation record
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auto curr = execution_context::current().ptr_;
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// placment new for control structure on fast-context stack
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return ::new ( sp) capture_t{
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palloc.sctx, salloc, fctx, curr.get(), std::forward< Fn >( fn), std::forward< Args >( args) ... };
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}
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execution_context() noexcept :
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// default constructed with current activation_record
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ptr_{ detail::activation_record::current_rec } {
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}
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public:
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static execution_context current() noexcept;
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#if defined(BOOST_USE_SEGMENTED_STACKS)
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template< typename Fn,
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typename ... Args,
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typename = detail::disable_overload< execution_context, Fn >
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>
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execution_context( Fn && fn, Args && ... args) :
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// deferred execution of fn and its arguments
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// arguments are stored in std::tuple<>
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// non-type template parameter pack via std::index_sequence_for<>
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// preserves the number of arguments
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// used to extract the function arguments from std::tuple<>
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ptr_{ create_context( segmented_stack(),
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std::forward< Fn >( fn),
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std::forward< Args >( args) ...) } {
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ptr_->resume( ptr_.get() );
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}
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template< typename Fn,
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typename ... Args
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>
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execution_context( std::allocator_arg_t, segmented_stack salloc, Fn && fn, Args && ... args) :
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// deferred execution of fn and its arguments
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// arguments are stored in std::tuple<>
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// non-type template parameter pack via std::index_sequence_for<>
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// preserves the number of arguments
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// used to extract the function arguments from std::tuple<>
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ptr_{ create_context( salloc,
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std::forward< Fn >( fn),
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std::forward< Args >( args) ...) } {
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ptr_->resume( ptr_.get() );
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}
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template< typename Fn,
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typename ... Args
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>
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execution_context( std::allocator_arg_t, preallocated palloc, segmented_stack salloc, Fn && fn, Args && ... args) :
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// deferred execution of fn and its arguments
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// arguments are stored in std::tuple<>
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// non-type template parameter pack via std::index_sequence_for<>
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// preserves the number of arguments
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// used to extract the function arguments from std::tuple<>
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ptr_{ create_context( palloc, salloc,
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std::forward< Fn >( fn),
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std::forward< Args >( args) ...) } {
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ptr_->resume( ptr_.get() );
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}
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#else
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template< typename Fn,
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typename ... Args,
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typename = detail::disable_overload< execution_context, Fn >
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>
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execution_context( Fn && fn, Args && ... args) :
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// deferred execution of fn and its arguments
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// arguments are stored in std::tuple<>
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// non-type template parameter pack via std::index_sequence_for<>
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// preserves the number of arguments
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// used to extract the function arguments from std::tuple<>
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ptr_{ create_context( fixedsize_stack(),
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std::forward< Fn >( fn),
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std::forward< Args >( args) ...) } {
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ptr_->resume( ptr_.get() );
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}
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template< typename StackAlloc,
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typename Fn,
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typename ... Args
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>
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execution_context( std::allocator_arg_t, StackAlloc salloc, Fn && fn, Args && ... args) :
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// deferred execution of fn and its arguments
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// arguments are stored in std::tuple<>
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// non-type template parameter pack via std::index_sequence_for<>
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// preserves the number of arguments
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// used to extract the function arguments from std::tuple<>
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ptr_{ create_context( salloc,
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std::forward< Fn >( fn),
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std::forward< Args >( args) ...) } {
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ptr_->resume( ptr_.get() );
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}
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template< typename StackAlloc,
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typename Fn,
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typename ... Args
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>
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execution_context( std::allocator_arg_t, preallocated palloc, StackAlloc salloc, Fn && fn, Args && ... args) :
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// deferred execution of fn and its arguments
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// arguments are stored in std::tuple<>
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// non-type template parameter pack via std::index_sequence_for<>
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// preserves the number of arguments
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// used to extract the function arguments from std::tuple<>
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ptr_{ create_context( palloc, salloc,
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std::forward< Fn >( fn),
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std::forward< Args >( args) ...) } {
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ptr_->resume( ptr_.get() );
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}
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#endif
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execution_context( execution_context const& other) noexcept :
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ptr_{ other.ptr_ } {
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}
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execution_context( execution_context && other) noexcept :
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ptr_{ other.ptr_ } {
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other.ptr_.reset();
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}
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execution_context & operator=( execution_context const& other) noexcept {
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// intrusive_ptr<> does not test for self-assignment
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if ( this == & other) return * this;
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ptr_ = other.ptr_;
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return * this;
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}
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execution_context & operator=( execution_context && other) noexcept {
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if ( this == & other) return * this;
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execution_context tmp{ std::move( other) };
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swap( tmp);
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return * this;
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}
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void * operator()( void * vp = nullptr) {
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return ptr_->resume( vp);
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}
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template< typename Fn >
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void * operator()( exec_ontop_arg_t, Fn && fn, void * vp = nullptr) {
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return ptr_->resume_ontop( vp,
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std::forward< Fn >( fn) );
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}
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explicit operator bool() const noexcept {
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return nullptr != ptr_.get();
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}
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bool operator!() const noexcept {
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return nullptr == ptr_.get();
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}
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bool operator==( execution_context const& other) const noexcept {
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return ptr_ == other.ptr_;
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}
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bool operator!=( execution_context const& other) const noexcept {
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return ptr_ != other.ptr_;
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}
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bool operator<( execution_context const& other) const noexcept {
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return ptr_ < other.ptr_;
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}
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bool operator>( execution_context const& other) const noexcept {
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return other.ptr_ < ptr_;
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}
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bool operator<=( execution_context const& other) const noexcept {
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return ! ( * this > other);
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}
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bool operator>=( execution_context const& other) const noexcept {
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return ! ( * this < other);
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}
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template< typename charT, class traitsT >
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friend std::basic_ostream< charT, traitsT > &
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operator<<( std::basic_ostream< charT, traitsT > & os, execution_context const& other) {
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if ( nullptr != other.ptr_) {
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return os << other.ptr_;
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} else {
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return os << "{not-a-context}";
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}
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}
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void swap( execution_context & other) noexcept {
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ptr_.swap( other.ptr_);
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}
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};
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inline
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void swap( execution_context & l, execution_context & r) noexcept {
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l.swap( r);
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}
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}}
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#ifdef BOOST_HAS_ABI_HEADERS
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# include BOOST_ABI_SUFFIX
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#endif
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#endif // BOOST_CONTEXT_EXECUTION_CONTEXT_H
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