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/*
* This program source code file is part of KiCad, a free EDA CAD application.
*
* Copyright (C) 2013 CERN
* @author Tomasz Wlostowski <tomasz.wlostowski@cern.ch>
* Copyright (C) 2016 KiCad Developers, see AUTHORS.txt for contributors.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, you may find one here:
* http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
* or you may search the http://www.gnu.org website for the version 2 license,
* or you may write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
*/
#ifndef __COROUTINE_H
#define __COROUTINE_H
#include <cstdlib>
#include <boost/version.hpp>
#include <type_traits>
#if BOOST_VERSION <= 106000
#include <boost/context/fcontext.hpp>
#else
#include <boost/context/execution_context.hpp>
#include <boost/context/protected_fixedsize_stack.hpp>
#endif
/**
* Class COROUNTINE.
* Implements a coroutine. Wikipedia has a good explanation:
*
* "Coroutines are computer program components that generalize subroutines to
* allow multiple entry points for suspending and resuming execution at certain locations.
* Coroutines are well-suited for implementing more familiar program components such as cooperative
* tasks, exceptions, event loop, iterators, infinite lists and pipes."
*
* In other words, a coroutine can be considered a lightweight thread - which can be
* preempted only when it deliberately yields the control to the caller. This way,
* we avoid concurrency problems such as locking / race conditions.
*
* Uses boost::context library to do the actual context switching.
*
* This particular version takes a DELEGATE as an entry point, so it can invoke
* methods within a given object as separate coroutines.
*
* See coroutine_example.cpp for sample code.
*/
template <typename ReturnType, typename ArgType>
class COROUTINE
{
public:
COROUTINE() :
COROUTINE( nullptr )
{
}
/**
* Constructor
* Creates a coroutine from a member method of an object
*/
template <class T>
COROUTINE( T* object, ReturnType(T::* ptr)( ArgType ) ) :
COROUTINE( std::bind( ptr, object, std::placeholders::_1 ) )
{
}
/**
* Constructor
* Creates a coroutine from a delegate object
*/
COROUTINE( std::function<ReturnType(ArgType)> aEntry ) :
m_func( std::move( aEntry ) ),
m_running( false ),
#if BOOST_VERSION <= 106000
m_stack( nullptr ),
m_stackSize( c_defaultStackSize ),
#endif
m_caller( nullptr ),
m_callee( nullptr )
{
// Avoid not initialized members, and make static analysers quiet
m_args = 0;
m_retVal = 0;
}
~COROUTINE()
{
#if BOOST_VERSION >= 105600
delete m_callee;
#endif
#if BOOST_VERSION <= 106000
delete m_caller;
if( m_stack )
free( m_stack );
#endif
}
private:
#if BOOST_VERSION <= 106000
using context_type = boost::context::fcontext_t;
#else
using context_type = boost::context::execution_context<COROUTINE*>;
#endif
public:
/**
* Function Yield()
*
* Stops execution of the coroutine and returns control to the caller.
* After a yield, Call() or Resume() methods invoked by the caller will
* immediately return true, indicating that we are not done yet, just asleep.
*/
void Yield()
{
#if BOOST_VERSION <= 106000
jump( m_callee, m_caller, false );
#else
auto result = (*m_caller)( this );
*m_caller = std::move( std::get<0>( result ) );
#endif
}
/**
* Function Yield()
*
* Yield with a value - passes a value of given type to the caller.
* Useful for implementing generator objects.
*/
void Yield( ReturnType& aRetVal )
{
m_retVal = aRetVal;
#if BOOST_VERSION <= 106000
jump( m_callee, m_caller, false );
#else
m_caller( this );
#endif
}
/**
* Function SetEntry()
*
* Defines the entry point for the coroutine, if not set in the constructor.
*/
void SetEntry( std::function<ReturnType(ArgType)> aEntry )
{
m_func = std::move( aEntry );
}
/* Function Call()
*
* Starts execution of a coroutine, passing args as its arguments.
* @return true, if the coroutine has yielded and false if it has finished its
* execution (returned).
*/
bool Call( ArgType aArgs )
{
assert( m_callee == NULL );
assert( m_caller == NULL );
#if BOOST_VERSION <= 106000
// fixme: Clean up stack stuff. Add a guard
m_stack = malloc( c_defaultStackSize );
// align to 16 bytes
void* sp = (void*) ( ( ( (ptrdiff_t) m_stack ) + m_stackSize - 0xf ) & ( ~0x0f ) );
// correct the stack size
m_stackSize -= ( (size_t) m_stack + m_stackSize - (size_t) sp );
#endif
m_args = &aArgs;
#if BOOST_VERSION < 105600
m_callee = boost::context::make_fcontext( sp, m_stackSize, callerStub );
#elif BOOST_VERSION <= 106000
m_callee = new context_type( boost::context::make_fcontext( sp, m_stackSize, callerStub ) );
#else
m_callee = new context_type( std::allocator_arg_t(),
boost::context::protected_fixedsize_stack( c_defaultStackSize ), &COROUTINE::callerStub );
#endif
#if BOOST_VERSION <= 106000
m_caller = new context_type();
#endif
m_running = true;
// off we go!
#if BOOST_VERSION <= 106000
jump( m_caller, m_callee, reinterpret_cast<intptr_t>( this ) );
#else
auto result = (*m_callee)( this );
*m_callee = std::move( std::get<0>( result ) );
#endif
return m_running;
}
/**
* Function Resume()
*
* Resumes execution of a previously yielded coroutine.
* @return true, if the coroutine has yielded again and false if it has finished its
* execution (returned).
*/
bool Resume()
{
#if BOOST_VERSION <= 106000
jump( m_caller, m_callee, false );
#else
auto result = (*m_callee)( this );
*m_callee = std::move( std::get<0>( result ) );
#endif
return m_running;
}
/**
* Function ReturnValue()
*
* Returns the yielded value (the argument Yield() was called with)
*/
const ReturnType& ReturnValue() const
{
return m_retVal;
}
/**
* Function Running()
*
* @return true, if the coroutine is active
*/
bool Running() const
{
return m_running;
}
private:
static const int c_defaultStackSize = 2000000; // fixme: make configurable
/* real entry point of the coroutine */
#if BOOST_VERSION <= 106000
static void callerStub( intptr_t aData )
#else
static context_type callerStub( context_type caller, COROUTINE* cor )
#endif
{
// get pointer to self
#if BOOST_VERSION <= 106000
COROUTINE<ReturnType, ArgType>* cor = reinterpret_cast<COROUTINE<ReturnType, ArgType>*>( aData );
#else
cor->m_caller = &caller;
#endif
// call the coroutine method
cor->m_retVal = cor->m_func( *( cor->m_args ) );
cor->m_running = false;
// go back to wherever we came from.
#if BOOST_VERSION <= 106000
jump( cor->m_callee, cor->m_caller, 0 );
#else
return caller;
#endif
}
///> Wrapper for jump_fcontext to assure compatibility between different boost versions
#if BOOST_VERSION <= 106000
static inline intptr_t jump( context_type* aOld, context_type* aNew,
intptr_t aP, bool aPreserveFPU = true )
{
#if BOOST_VERSION < 105600
return boost::context::jump_fcontext( aOld, aNew, aP, aPreserveFPU );
#else
return boost::context::jump_fcontext( aOld, *aNew, aP, aPreserveFPU );
#endif
}
#endif
std::function<ReturnType(ArgType)> m_func;
bool m_running;
#if BOOST_VERSION <= 106000
///< coroutine stack
void* m_stack;
size_t m_stackSize;
#endif
///< pointer to coroutine entry arguments. Stripped of references
///< to avoid compiler errors.
typename std::remove_reference<ArgType>::type* m_args;
ReturnType m_retVal;
///< saved caller context
context_type* m_caller;
///< saved coroutine context
context_type* m_callee;
};
#endif
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