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-rw-r--r--boost/context/continuation_fcontext.hpp382
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+
+// Copyright Oliver Kowalke 2017.
+// 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_CONTINUATION_H
+#define BOOST_CONTEXT_CONTINUATION_H
+
+#include <boost/context/detail/config.hpp>
+
+#include <algorithm>
+#include <cstddef>
+#include <cstdint>
+#include <cstdlib>
+#include <exception>
+#include <functional>
+#include <memory>
+#include <ostream>
+#include <tuple>
+#include <utility>
+
+#include <boost/assert.hpp>
+#include <boost/config.hpp>
+#include <boost/intrusive_ptr.hpp>
+
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+#include <boost/context/detail/exchange.hpp>
+#endif
+#if defined(BOOST_NO_CXX17_STD_INVOKE)
+#include <boost/context/detail/invoke.hpp>
+#endif
+#include <boost/context/detail/disable_overload.hpp>
+#include <boost/context/detail/exception.hpp>
+#include <boost/context/detail/fcontext.hpp>
+#include <boost/context/detail/tuple.hpp>
+#include <boost/context/fixedsize_stack.hpp>
+#include <boost/context/flags.hpp>
+#include <boost/context/preallocated.hpp>
+#include <boost/context/segmented_stack.hpp>
+#include <boost/context/stack_context.hpp>
+
+#ifdef BOOST_HAS_ABI_HEADERS
+# include BOOST_ABI_PREFIX
+#endif
+
+#if defined(BOOST_MSVC)
+# pragma warning(push)
+# pragma warning(disable: 4702)
+#endif
+
+namespace boost {
+namespace context {
+namespace detail {
+
+inline
+transfer_t context_unwind( transfer_t t) {
+ throw forced_unwind( t.fctx);
+ return { nullptr, nullptr };
+}
+
+template< typename Rec >
+transfer_t context_exit( transfer_t t) noexcept {
+ Rec * rec = static_cast< Rec * >( t.data);
+ // destroy context stack
+ rec->deallocate();
+ return { nullptr, nullptr };
+}
+
+template< typename Rec >
+void context_entry( transfer_t t) noexcept {
+ // transfer control structure to the context-stack
+ Rec * rec = static_cast< Rec * >( t.data);
+ BOOST_ASSERT( nullptr != t.fctx);
+ BOOST_ASSERT( nullptr != rec);
+ try {
+ // jump back to `create_context()`
+ t = jump_fcontext( t.fctx, nullptr);
+ // start executing
+ t.fctx = rec->run( t.fctx);
+ } catch ( forced_unwind const& e) {
+ t = { e.fctx, nullptr };
+ }
+ BOOST_ASSERT( nullptr != t.fctx);
+ // destroy context-stack of `this`context on next context
+ ontop_fcontext( t.fctx, rec, context_exit< Rec >);
+ BOOST_ASSERT_MSG( false, "context already terminated");
+}
+
+template< typename Ctx, typename Fn >
+transfer_t context_ontop( transfer_t t) {
+ auto p = static_cast< std::tuple< Fn > * >( t.data);
+ BOOST_ASSERT( nullptr != p);
+ typename std::decay< Fn >::type fn = std::get< 0 >( * p);
+ t.data = nullptr;
+ Ctx c{ t.fctx };
+ // execute function, pass continuation via reference
+ fn( std::move( c) );
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+ return { exchange( c.fctx_, nullptr), nullptr };
+#else
+ return { std::exchange( c.fctx_, nullptr), nullptr };
+#endif
+}
+
+template< typename Ctx, typename StackAlloc, typename Fn >
+class record {
+private:
+ stack_context sctx_;
+ StackAlloc salloc_;
+ typename std::decay< Fn >::type fn_;
+
+ static void destroy( record * p) noexcept {
+ StackAlloc salloc = p->salloc_;
+ stack_context sctx = p->sctx_;
+ // deallocate record
+ p->~record();
+ // destroy stack with stack allocator
+ salloc.deallocate( sctx);
+ }
+
+public:
+ record( stack_context sctx, StackAlloc const& salloc,
+ Fn && fn) noexcept :
+ sctx_( sctx),
+ salloc_( salloc),
+ fn_( std::forward< Fn >( fn) ) {
+ }
+
+ record( record const&) = delete;
+ record & operator=( record const&) = delete;
+
+ void deallocate() noexcept {
+ destroy( this);
+ }
+
+ fcontext_t run( fcontext_t fctx) {
+ Ctx c{ fctx };
+ // invoke context-function
+#if defined(BOOST_NO_CXX17_STD_INVOKE)
+ c = invoke( fn_, std::move( c) );
+#else
+ c = std::invoke( fn_, std::move( c) );
+#endif
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+ return exchange( c.fctx_, nullptr);
+#else
+ return std::exchange( c.fctx_, nullptr);
+#endif
+ }
+};
+
+template< typename Record, typename StackAlloc, typename Fn >
+fcontext_t create_context1( StackAlloc salloc, Fn && fn) {
+ auto sctx = salloc.allocate();
+ // reserve space for control structure
+ void * storage = reinterpret_cast< void * >(
+ ( reinterpret_cast< uintptr_t >( sctx.sp) - static_cast< uintptr_t >( sizeof( Record) ) )
+ & ~static_cast< uintptr_t >( 0xff) );
+ // placment new for control structure on context stack
+ Record * record = new ( storage) Record{
+ sctx, salloc, std::forward< Fn >( fn) };
+ // 64byte gab between control structure and stack top
+ // should be 16byte aligned
+ void * stack_top = reinterpret_cast< void * >(
+ reinterpret_cast< uintptr_t >( storage) - static_cast< uintptr_t >( 64) );
+ void * stack_bottom = reinterpret_cast< void * >(
+ reinterpret_cast< uintptr_t >( sctx.sp) - static_cast< uintptr_t >( sctx.size) );
+ // create fast-context
+ const std::size_t size = reinterpret_cast< uintptr_t >( stack_top) - reinterpret_cast< uintptr_t >( stack_bottom);
+ const fcontext_t fctx = make_fcontext( stack_top, size, & context_entry< Record >);
+ BOOST_ASSERT( nullptr != fctx);
+ // transfer control structure to context-stack
+ return jump_fcontext( fctx, record).fctx;
+}
+
+template< typename Record, typename StackAlloc, typename Fn >
+fcontext_t create_context2( preallocated palloc, StackAlloc salloc, Fn && fn) {
+ // reserve space for control structure
+ void * storage = reinterpret_cast< void * >(
+ ( reinterpret_cast< uintptr_t >( palloc.sp) - static_cast< uintptr_t >( sizeof( Record) ) )
+ & ~ static_cast< uintptr_t >( 0xff) );
+ // placment new for control structure on context-stack
+ Record * record = new ( storage) Record{
+ palloc.sctx, salloc, std::forward< Fn >( fn) };
+ // 64byte gab between control structure and stack top
+ void * stack_top = reinterpret_cast< void * >(
+ reinterpret_cast< uintptr_t >( storage) - static_cast< uintptr_t >( 64) );
+ void * stack_bottom = reinterpret_cast< void * >(
+ reinterpret_cast< uintptr_t >( palloc.sctx.sp) - static_cast< uintptr_t >( palloc.sctx.size) );
+ // create fast-context
+ const std::size_t size = reinterpret_cast< uintptr_t >( stack_top) - reinterpret_cast< uintptr_t >( stack_bottom);
+ const fcontext_t fctx = make_fcontext( stack_top, size, & context_entry< Record >);
+ BOOST_ASSERT( nullptr != fctx);
+ // transfer control structure to context-stack
+ return jump_fcontext( fctx, record).fctx;
+}
+
+}
+
+class continuation {
+private:
+ template< typename Ctx, typename StackAlloc, typename Fn >
+ friend class detail::record;
+
+ template< typename Ctx, typename Fn >
+ friend detail::transfer_t
+ detail::context_ontop( detail::transfer_t);
+
+ template< typename StackAlloc, typename Fn >
+ friend continuation
+ callcc( std::allocator_arg_t, StackAlloc, Fn &&);
+
+ template< typename StackAlloc, typename Fn >
+ friend continuation
+ callcc( std::allocator_arg_t, preallocated, StackAlloc, Fn &&);
+
+ detail::fcontext_t fctx_{ nullptr };
+
+ continuation( detail::fcontext_t fctx) noexcept :
+ fctx_{ fctx } {
+ }
+
+public:
+ continuation() noexcept = default;
+
+ ~continuation() {
+ if ( BOOST_UNLIKELY( nullptr != fctx_) ) {
+ detail::ontop_fcontext(
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+ detail::exchange( fctx_, nullptr),
+#else
+ std::exchange( fctx_, nullptr),
+#endif
+ nullptr,
+ detail::context_unwind);
+ }
+ }
+
+ continuation( continuation && other) noexcept {
+ std::swap( fctx_, other.fctx_);
+ }
+
+ continuation & operator=( continuation && other) noexcept {
+ if ( BOOST_LIKELY( this != & other) ) {
+ continuation tmp = std::move( other);
+ swap( tmp);
+ }
+ return * this;
+ }
+
+ continuation( continuation const& other) noexcept = delete;
+ continuation & operator=( continuation const& other) noexcept = delete;
+
+ continuation resume() {
+ BOOST_ASSERT( nullptr != fctx_);
+ return detail::jump_fcontext(
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+ detail::exchange( fctx_, nullptr),
+#else
+ std::exchange( fctx_, nullptr),
+#endif
+ nullptr).fctx;
+ }
+
+ template< typename Fn >
+ continuation resume_with( Fn && fn) {
+ BOOST_ASSERT( nullptr != fctx_);
+ auto p = std::make_tuple( std::forward< Fn >( fn) );
+ return detail::ontop_fcontext(
+#if defined(BOOST_NO_CXX14_STD_EXCHANGE)
+ detail::exchange( fctx_, nullptr),
+#else
+ std::exchange( fctx_, nullptr),
+#endif
+ & p,
+ detail::context_ontop< continuation, Fn >).fctx;
+ }
+
+ explicit operator bool() const noexcept {
+ return nullptr != fctx_;
+ }
+
+ bool operator!() const noexcept {
+ return nullptr == fctx_;
+ }
+
+ bool operator==( continuation const& other) const noexcept {
+ return fctx_ == other.fctx_;
+ }
+
+ bool operator!=( continuation const& other) const noexcept {
+ return fctx_ != other.fctx_;
+ }
+
+ bool operator<( continuation const& other) const noexcept {
+ return fctx_ < other.fctx_;
+ }
+
+ bool operator>( continuation const& other) const noexcept {
+ return other.fctx_ < fctx_;
+ }
+
+ bool operator<=( continuation const& other) const noexcept {
+ return ! ( * this > other);
+ }
+
+ bool operator>=( continuation const& other) const noexcept {
+ return ! ( * this < other);
+ }
+
+ template< typename charT, class traitsT >
+ friend std::basic_ostream< charT, traitsT > &
+ operator<<( std::basic_ostream< charT, traitsT > & os, continuation const& other) {
+ if ( nullptr != other.fctx_) {
+ return os << other.fctx_;
+ } else {
+ return os << "{not-a-context}";
+ }
+ }
+
+ void swap( continuation & other) noexcept {
+ std::swap( fctx_, other.fctx_);
+ }
+};
+
+template<
+ typename Fn,
+ typename = detail::disable_overload< continuation, Fn >
+>
+continuation
+callcc( Fn && fn) {
+ return callcc(
+ std::allocator_arg, fixedsize_stack(),
+ std::forward< Fn >( fn) );
+}
+
+template< typename StackAlloc, typename Fn >
+continuation
+callcc( std::allocator_arg_t, StackAlloc salloc, Fn && fn) {
+ using Record = detail::record< continuation, StackAlloc, Fn >;
+ return continuation{
+ detail::create_context1< Record >(
+ salloc, std::forward< Fn >( fn) ) }.resume();
+}
+
+template< typename StackAlloc, typename Fn >
+continuation
+callcc( std::allocator_arg_t, preallocated palloc, StackAlloc salloc, Fn && fn) {
+ using Record = detail::record< continuation, StackAlloc, Fn >;
+ return continuation{
+ detail::create_context2< Record >(
+ palloc, salloc, std::forward< Fn >( fn) ) }.resume();
+}
+
+#if defined(BOOST_USE_SEGMENTED_STACKS)
+template< typename Fn >
+continuation
+callcc( std::allocator_arg_t, segmented_stack, Fn &&);
+
+template< typename StackAlloc, typename Fn >
+continuation
+callcc( std::allocator_arg_t, preallocated, segmented_stack, Fn &&);
+#endif
+
+// swap
+inline
+void swap( continuation & l, continuation & r) noexcept {
+ l.swap( r);
+}
+
+}}
+
+#if defined(BOOST_MSVC)
+# pragma warning(pop)
+#endif
+
+#ifdef BOOST_HAS_ABI_HEADERS
+# include BOOST_ABI_SUFFIX
+#endif
+
+#endif // BOOST_CONTEXT_CONTINUATION_H