371 lines
12 KiB
C++
Executable File
371 lines
12 KiB
C++
Executable File
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// Copyright Oliver Kowalke 2017.
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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_CONTINUATION_H
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#define BOOST_CONTEXT_CONTINUATION_H
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#include <boost/context/detail/config.hpp>
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#include <algorithm>
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#include <cstddef>
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#include <cstdint>
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#include <cstdlib>
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#include <exception>
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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_CXX14_STD_EXCHANGE)
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#include <boost/context/detail/exchange.hpp>
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#endif
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#if defined(BOOST_NO_CXX17_STD_INVOKE)
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#include <boost/context/detail/invoke.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/exception.hpp>
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#include <boost/context/detail/fcontext.hpp>
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#include <boost/context/detail/tuple.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_MSVC)
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# pragma warning(push)
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# pragma warning(disable: 4702)
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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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inline
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transfer_t context_unwind( transfer_t t) {
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throw forced_unwind( t.fctx);
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return { nullptr, nullptr };
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}
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template< typename Rec >
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transfer_t context_exit( transfer_t t) noexcept {
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Rec * rec = static_cast< Rec * >( t.data);
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// destroy context stack
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rec->deallocate();
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return { nullptr, nullptr };
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}
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template< typename Rec >
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void context_entry( transfer_t t) noexcept {
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// transfer control structure to the context-stack
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Rec * rec = static_cast< Rec * >( t.data);
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BOOST_ASSERT( nullptr != t.fctx);
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BOOST_ASSERT( nullptr != rec);
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try {
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// jump back to `create_context()`
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t = jump_fcontext( t.fctx, nullptr);
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// start executing
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t.fctx = rec->run( t.fctx);
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} catch ( forced_unwind const& ex) {
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t = { ex.fctx, nullptr };
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}
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BOOST_ASSERT( nullptr != t.fctx);
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// destroy context-stack of `this`context on next context
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ontop_fcontext( t.fctx, rec, context_exit< Rec >);
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BOOST_ASSERT_MSG( false, "context already terminated");
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}
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template< typename Ctx, typename Fn >
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transfer_t context_ontop( transfer_t t) {
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auto p = static_cast< std::tuple< Fn > * >( t.data);
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BOOST_ASSERT( nullptr != p);
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typename std::decay< Fn >::type fn = std::get< 0 >( * p);
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t.data = nullptr;
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Ctx c{ t.fctx };
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// execute function, pass continuation via reference
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c = fn( std::move( c) );
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#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
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return { exchange( c.fctx_, nullptr), nullptr };
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#else
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return { std::exchange( c.fctx_, nullptr), nullptr };
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#endif
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}
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template< typename Ctx, typename StackAlloc, typename Fn >
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class record {
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private:
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stack_context sctx_;
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typename std::decay< StackAlloc >::type salloc_;
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typename std::decay< Fn >::type fn_;
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static void destroy( record * p) noexcept {
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typename std::decay< StackAlloc >::type salloc = std::move( p->salloc_);
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stack_context sctx = p->sctx_;
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// deallocate record
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p->~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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record( stack_context sctx, StackAlloc && salloc,
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Fn && fn) noexcept :
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sctx_( sctx),
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salloc_( std::forward< StackAlloc >( salloc)),
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fn_( std::forward< Fn >( fn) ) {
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}
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record( record const&) = delete;
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record & operator=( record const&) = delete;
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void deallocate() noexcept {
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destroy( this);
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}
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fcontext_t run( fcontext_t fctx) {
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Ctx c{ fctx };
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// invoke context-function
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#if defined(BOOST_NO_CXX17_STD_INVOKE)
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c = boost::context::detail::invoke( fn_, std::move( c) );
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#else
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c = std::invoke( fn_, std::move( c) );
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#endif
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#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
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return exchange( c.fctx_, nullptr);
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#else
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return std::exchange( c.fctx_, nullptr);
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#endif
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}
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};
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template< typename Record, typename StackAlloc, typename Fn >
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fcontext_t create_context1( StackAlloc && salloc, Fn && fn) {
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auto sctx = salloc.allocate();
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// reserve space for control structure
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void * storage = reinterpret_cast< void * >(
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( reinterpret_cast< uintptr_t >( sctx.sp) - static_cast< uintptr_t >( sizeof( Record) ) )
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& ~static_cast< uintptr_t >( 0xff) );
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// placment new for control structure on context stack
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Record * record = new ( storage) Record{
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sctx, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) };
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// 64byte gab between control structure and stack top
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// should be 16byte aligned
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void * stack_top = reinterpret_cast< void * >(
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reinterpret_cast< uintptr_t >( storage) - static_cast< uintptr_t >( 64) );
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void * stack_bottom = reinterpret_cast< void * >(
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reinterpret_cast< uintptr_t >( sctx.sp) - static_cast< uintptr_t >( sctx.size) );
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// create fast-context
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const std::size_t size = reinterpret_cast< uintptr_t >( stack_top) - reinterpret_cast< uintptr_t >( stack_bottom);
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const fcontext_t fctx = make_fcontext( stack_top, size, & context_entry< Record >);
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BOOST_ASSERT( nullptr != fctx);
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// transfer control structure to context-stack
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return jump_fcontext( fctx, record).fctx;
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}
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template< typename Record, typename StackAlloc, typename Fn >
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fcontext_t create_context2( preallocated palloc, StackAlloc && salloc, Fn && fn) {
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// reserve space for control structure
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void * storage = reinterpret_cast< void * >(
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( reinterpret_cast< uintptr_t >( palloc.sp) - static_cast< uintptr_t >( sizeof( Record) ) )
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& ~ static_cast< uintptr_t >( 0xff) );
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// placment new for control structure on context-stack
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Record * record = new ( storage) Record{
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palloc.sctx, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) };
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// 64byte gab between control structure and stack top
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void * stack_top = reinterpret_cast< void * >(
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reinterpret_cast< uintptr_t >( storage) - static_cast< uintptr_t >( 64) );
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void * stack_bottom = reinterpret_cast< void * >(
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reinterpret_cast< uintptr_t >( palloc.sctx.sp) - static_cast< uintptr_t >( palloc.sctx.size) );
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// create fast-context
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const std::size_t size = reinterpret_cast< uintptr_t >( stack_top) - reinterpret_cast< uintptr_t >( stack_bottom);
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const fcontext_t fctx = make_fcontext( stack_top, size, & context_entry< Record >);
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BOOST_ASSERT( nullptr != fctx);
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// transfer control structure to context-stack
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return jump_fcontext( fctx, record).fctx;
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}
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}
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class continuation {
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private:
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template< typename Ctx, typename StackAlloc, typename Fn >
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friend class detail::record;
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template< typename Ctx, typename Fn >
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friend detail::transfer_t
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detail::context_ontop( detail::transfer_t);
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template< typename StackAlloc, typename Fn >
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friend continuation
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callcc( std::allocator_arg_t, StackAlloc &&, Fn &&);
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template< typename StackAlloc, typename Fn >
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friend continuation
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callcc( std::allocator_arg_t, preallocated, StackAlloc &&, Fn &&);
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detail::fcontext_t fctx_{ nullptr };
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continuation( detail::fcontext_t fctx) noexcept :
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fctx_{ fctx } {
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}
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public:
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continuation() noexcept = default;
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~continuation() {
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if ( BOOST_UNLIKELY( nullptr != fctx_) ) {
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detail::ontop_fcontext(
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#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
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detail::exchange( fctx_, nullptr),
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#else
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std::exchange( fctx_, nullptr),
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#endif
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nullptr,
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detail::context_unwind);
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}
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}
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continuation( continuation && other) noexcept {
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swap( other);
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}
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continuation & operator=( continuation && other) noexcept {
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if ( BOOST_LIKELY( this != & other) ) {
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continuation tmp = std::move( other);
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swap( tmp);
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}
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return * this;
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}
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continuation( continuation const& other) noexcept = delete;
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continuation & operator=( continuation const& other) noexcept = delete;
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continuation resume() & {
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return std::move( * this).resume();
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}
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continuation resume() && {
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BOOST_ASSERT( nullptr != fctx_);
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return { detail::jump_fcontext(
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#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
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detail::exchange( fctx_, nullptr),
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#else
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std::exchange( fctx_, nullptr),
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#endif
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nullptr).fctx };
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}
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template< typename Fn >
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continuation resume_with( Fn && fn) & {
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return std::move( * this).resume_with( std::forward< Fn >( fn) );
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}
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template< typename Fn >
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continuation resume_with( Fn && fn) && {
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BOOST_ASSERT( nullptr != fctx_);
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auto p = std::make_tuple( std::forward< Fn >( fn) );
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return { detail::ontop_fcontext(
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#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
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detail::exchange( fctx_, nullptr),
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#else
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std::exchange( fctx_, nullptr),
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#endif
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& p,
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detail::context_ontop< continuation, Fn >).fctx };
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}
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explicit operator bool() const noexcept {
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return nullptr != fctx_;
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}
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bool operator!() const noexcept {
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return nullptr == fctx_;
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}
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bool operator<( continuation const& other) const noexcept {
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return fctx_ < other.fctx_;
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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, continuation const& other) {
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if ( nullptr != other.fctx_) {
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return os << other.fctx_;
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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( continuation & other) noexcept {
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std::swap( fctx_, other.fctx_);
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}
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};
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template<
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typename Fn,
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typename = detail::disable_overload< continuation, Fn >
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>
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continuation
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callcc( Fn && fn) {
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return callcc(
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std::allocator_arg, fixedsize_stack(),
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std::forward< Fn >( fn) );
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}
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template< typename StackAlloc, typename Fn >
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continuation
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callcc( std::allocator_arg_t, StackAlloc && salloc, Fn && fn) {
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using Record = detail::record< continuation, StackAlloc, Fn >;
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return continuation{
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detail::create_context1< Record >(
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std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) ) }.resume();
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}
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template< typename StackAlloc, typename Fn >
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continuation
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callcc( std::allocator_arg_t, preallocated palloc, StackAlloc && salloc, Fn && fn) {
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using Record = detail::record< continuation, StackAlloc, Fn >;
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return continuation{
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detail::create_context2< Record >(
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palloc, std::forward< StackAlloc >( salloc), std::forward< Fn >( fn) ) }.resume();
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}
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#if defined(BOOST_USE_SEGMENTED_STACKS)
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template< typename Fn >
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continuation
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callcc( std::allocator_arg_t, segmented_stack, Fn &&);
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template< typename StackAlloc, typename Fn >
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continuation
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callcc( std::allocator_arg_t, preallocated, segmented_stack, Fn &&);
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#endif
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inline
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void swap( continuation & l, continuation & r) noexcept {
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l.swap( r);
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}
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}}
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#if defined(BOOST_MSVC)
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# pragma warning(pop)
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#endif
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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_CONTINUATION_H
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