339 lines
9.4 KiB
C++
339 lines
9.4 KiB
C++
/*
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* This program source code file is part of KiCad, a free EDA CAD application.
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*
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* Copyright (C) 2013 CERN
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* @author Tomasz Wlostowski <tomasz.wlostowski@cern.ch>
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* Copyright (C) 2016 KiCad Developers, see AUTHORS.txt for contributors.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, you may find one here:
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* http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
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* or you may search the http://www.gnu.org website for the version 2 license,
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* or you may write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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#ifndef __COROUTINE_H
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#define __COROUTINE_H
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#include <cstdlib>
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#include <boost/version.hpp>
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#include <type_traits>
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#if BOOST_VERSION < 106100
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#include <boost/context/fcontext.hpp>
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#else
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#include <boost/context/execution_context.hpp>
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#include <boost/context/protected_fixedsize_stack.hpp>
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#endif
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/**
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* Note: in the history of boost, two changes to the context interface happened.
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* [1.54, 1.56)
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* http://www.boost.org/doc/libs/1_55_0/libs/context/doc/html/context/context/boost_fcontext.html
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* intptr_t jump_fcontext(
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* fcontext_t* ofc,
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* fcontext_t const* nfc,
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* intptr_t vp,
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* bool preserve_fpu = true
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* );
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*
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* fcontext_t* make_fcontext(
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* void* sp,
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* std::size_t size,
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* void (*fn)(intptr_t)
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* );
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*
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* [1.56, 1.61)
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* http://www.boost.org/doc/libs/1_56_0/libs/context/doc/html/context/context/boost_fcontext.html
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* intptr_t jump_fcontext(
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* fcontext_t* ofc,
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* fcontext_t nfc, <-----
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* intptr_t vp,
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* bool preserve_fpu = true
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* );
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*
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* fcontext_t make_fcontext( <-----
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* void* sp,
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* std::size_t size,
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* void(*fn)(intptr_t)
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* );
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*
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* [1.61, oo)
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* http://www.boost.org/doc/libs/1_61_0/libs/context/doc/html/context/ecv2.html
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* fcontext_t is hidden away behind the boost::execution_context(_v2) and the stack is created on behalf of
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* the user.
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*/
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/**
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* Class COROUNTINE.
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* Implements a coroutine. Wikipedia has a good explanation:
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*
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* "Coroutines are computer program components that generalize subroutines to
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* allow multiple entry points for suspending and resuming execution at certain locations.
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* Coroutines are well-suited for implementing more familiar program components such as cooperative
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* tasks, exceptions, event loop, iterators, infinite lists and pipes."
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*
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* In other words, a coroutine can be considered a lightweight thread - which can be
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* preempted only when it deliberately yields the control to the caller. This way,
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* we avoid concurrency problems such as locking / race conditions.
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*
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* Uses boost::context library to do the actual context switching.
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*
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* This particular version takes a DELEGATE as an entry point, so it can invoke
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* methods within a given object as separate coroutines.
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*
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* See coroutine_example.cpp for sample code.
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*/
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template <typename ReturnType, typename ArgType>
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class COROUTINE
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{
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public:
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COROUTINE() :
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COROUTINE( nullptr )
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{
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}
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/**
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* Constructor
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* Creates a coroutine from a member method of an object
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*/
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template <class T>
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COROUTINE( T* object, ReturnType(T::*ptr)( ArgType ) ) :
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COROUTINE( std::bind( ptr, object, std::placeholders::_1 ) )
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{
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}
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/**
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* Constructor
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* Creates a coroutine from a delegate object
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*/
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COROUTINE( std::function<ReturnType(ArgType)> aEntry ) :
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m_func( std::move( aEntry ) ),
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m_running( false ),
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m_args( 0 ),
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#if BOOST_VERSION < 106100 // -> m_callee = void* or void**
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m_callee( nullptr ),
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#endif
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m_retVal( 0 )
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{
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}
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~COROUTINE()
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{
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}
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private:
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#if BOOST_VERSION < 106100
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using context_type = boost::context::fcontext_t;
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#else
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using context_type = boost::context::execution_context<COROUTINE*>;
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#endif
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public:
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/**
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* Function Yield()
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*
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* Stops execution of the coroutine and returns control to the caller.
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* After a yield, Call() or Resume() methods invoked by the caller will
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* immediately return true, indicating that we are not done yet, just asleep.
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*/
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void Yield()
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{
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jumpOut();
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}
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/**
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* Function Yield()
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*
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* Yield with a value - passes a value of given type to the caller.
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* Useful for implementing generator objects.
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*/
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void Yield( ReturnType& aRetVal )
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{
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m_retVal = aRetVal;
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jumpOut();
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}
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/**
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* Function Resume()
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*
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* Resumes execution of a previously yielded coroutine.
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* @return true, if the coroutine has yielded again and false if it has finished its
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* execution (returned).
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*/
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bool Resume()
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{
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jumpIn();
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return m_running;
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}
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/**
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* Function SetEntry()
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*
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* Defines the entry point for the coroutine, if not set in the constructor.
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*/
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void SetEntry( std::function<ReturnType(ArgType)> aEntry )
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{
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m_func = std::move( aEntry );
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}
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/* Function Call()
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*
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* Starts execution of a coroutine, passing args as its arguments.
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* @return true, if the coroutine has yielded and false if it has finished its
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* execution (returned).
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*/
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bool Call( ArgType aArgs )
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{
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assert( m_func );
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assert( !m_callee );
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m_args = &aArgs;
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#if BOOST_VERSION < 106100
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assert( m_stack == nullptr );
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// fixme: Clean up stack stuff. Add a guard
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size_t stackSize = c_defaultStackSize;
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m_stack.reset( new char[stackSize] );
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// align to 16 bytes
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void* sp = (void*) ( ( ( (ptrdiff_t) m_stack.get() ) + stackSize - 0xf ) & ( ~0x0f ) );
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// correct the stack size
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stackSize -= size_t( ( (ptrdiff_t) m_stack.get() + stackSize) - (ptrdiff_t) sp );
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m_callee = boost::context::make_fcontext( sp, stackSize, callerStub );
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#else
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m_callee = context_type(
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std::allocator_arg_t(),
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boost::context::protected_fixedsize_stack( c_defaultStackSize ),
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&COROUTINE::callerStub
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);
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#endif
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m_running = true;
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// off we go!
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jumpIn();
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return m_running;
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}
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/**
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* Function ReturnValue()
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*
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* Returns the yielded value (the argument Yield() was called with)
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*/
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const ReturnType& ReturnValue() const
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{
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return m_retVal;
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}
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/**
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* Function Running()
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*
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* @return true, if the coroutine is active
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*/
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bool Running() const
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{
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return m_running;
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}
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private:
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static const int c_defaultStackSize = 2000000; // fixme: make configurable
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/* real entry point of the coroutine */
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#if BOOST_VERSION < 106100
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static void callerStub( intptr_t aData )
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{
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// get pointer to self
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COROUTINE* cor = reinterpret_cast<COROUTINE*>( aData );
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// call the coroutine method
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cor->m_retVal = cor->m_func( *(cor->m_args) );
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cor->m_running = false;
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// go back to wherever we came from.
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cor->jumpOut();
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}
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#else
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/* real entry point of the coroutine */
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static context_type callerStub( context_type caller, COROUTINE* cor )
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{
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cor->m_caller = std::move( caller );
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// call the coroutine method
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cor->m_retVal = cor->m_func( *(cor->m_args) );
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cor->m_running = false;
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// go back to wherever we came from.
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return std::move( cor->m_caller );
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}
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#endif
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void jumpIn()
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{
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#if BOOST_VERSION < 105600
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boost::context::jump_fcontext( &m_caller, m_callee, reinterpret_cast<intptr_t>(this) );
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#elif BOOST_VERSION < 106100
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boost::context::jump_fcontext( &m_caller, m_callee, reinterpret_cast<intptr_t>(this) );
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#else
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auto result = m_callee( this );
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m_callee = std::move( std::get<0>( result ) );
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#endif
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}
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void jumpOut()
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{
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#if BOOST_VERSION < 105600
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boost::context::jump_fcontext( m_callee, &m_caller, 0 );
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#elif BOOST_VERSION < 106100
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boost::context::jump_fcontext( &m_callee, m_caller, 0 );
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#else
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auto result = m_caller( nullptr );
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m_caller = std::move( std::get<0>( result ) );
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#endif
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}
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std::function<ReturnType(ArgType)> m_func;
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bool m_running;
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#if BOOST_VERSION < 106100
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///< coroutine stack
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std::unique_ptr<char[]> m_stack;
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#endif
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///< pointer to coroutine entry arguments. Stripped of references
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///< to avoid compiler errors.
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typename std::remove_reference<ArgType>::type* m_args;
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///< saved caller context
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context_type m_caller;
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///< saved coroutine context
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#if BOOST_VERSION < 105600
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context_type* m_callee;
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#else
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context_type m_callee;
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#endif
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ReturnType m_retVal;
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};
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#endif
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