/*
* Copyright (c) 2018 ARM Limited
* All rights reserved
*
* The license below extends only to copyright in the software and shall
* not be construed as granting a license to any other intellectual
* property including but not limited to intellectual property relating
* to a hardware implementation of the functionality of the software
* licensed hereunder. You may use the software subject to the license
* terms below provided that you ensure that this notice is replicated
* unmodified and in its entirety in all distributions of the software,
* modified or unmodified, in source code or in binary form.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Authors: Giacomo Travaglini
*/
#ifndef __BASE_COROUTINE_HH__
#define __BASE_COROUTINE_HH__
#include <functional>
#include <stack>
#include "base/fiber.hh"
namespace m5
{
/**
* This template defines a Coroutine wrapper type with a Boost-like
* interface. It is built on top of the gem5 fiber class.
* The two template parameters (Arg and Ret) are the coroutine
* argument and coroutine return types which are passed between
* the coroutine and the caller via operator() and get() method.
* This implementation doesn't support passing multiple values,
* so a tuple must be used in that scenario.
*
* Most methods are templatized since it is relevant to distinguish
* the cases where one or both of the template parameters are void
*/
template <typename Arg, typename Ret>
class Coroutine : public Fiber
{
// This empty struct type is meant to replace coroutine channels
// in case the channel should be void (Coroutine template parameters
// are void. (See following ArgChannel, RetChannel typedef)
struct Empty {};
using ArgChannel = typename std::conditional<
std::is_same<Arg, void>::value, Empty, std::stack<Arg>>::type;
using RetChannel = typename std::conditional<
std::is_same<Ret, void>::value, Empty, std::stack<Ret>>::type;
public:
/**
* CallerType:
* A reference to an object of this class will be passed
* to the coroutine task. This is the way it is possible
* for the coroutine to interface (e.g. switch back)
* to the coroutine caller.
*/
class CallerType
{
friend class Coroutine;
protected:
CallerType(Coroutine& _coro) : coro(_coro), callerFiber(nullptr) {}
public:
/**
* operator() is the way we can jump outside the coroutine
* and return a value to the caller.
*
* This method is generated only if the coroutine returns
* a value (Ret != void)
*/
template <typename T = Ret>
CallerType&
operator()(typename std::enable_if<
!std::is_same<T, void>::value, T>::type param)
{
retChannel.push(param);
callerFiber->run();
return *this;
}
/**
* operator() is the way we can jump outside the coroutine
*
* This method is generated only if the coroutine doesn't
* return a value (Ret = void)
*/
template <typename T = Ret>
typename std::enable_if<std::is_same<T, void>::value,
CallerType>::type&
operator()()
{
callerFiber->run();
return *this;
}
/**
* get() is the way we can extrapolate arguments from the
* coroutine caller.
* The coroutine blocks, waiting for the value, unless it is already
* available; otherwise caller execution is resumed,
* and coroutine won't execute until a value is pushed
* from the caller.
*
* @return arg coroutine argument
*/
template <typename T = Arg>
typename std::enable_if<!std::is_same<T, void>::value, T>::type
get()
{
auto& args_channel = coro.argsChannel;
while (args_channel.empty()) {
callerFiber->run();
}
auto ret = args_channel.top();
args_channel.pop();
return ret;
}
private:
Coroutine& coro;
Fiber* callerFiber;
RetChannel retChannel;
};
Coroutine() = delete;
Coroutine(const Coroutine& rhs) = delete;
Coroutine& operator=(const Coroutine& rhs) = delete;
/**
* Coroutine constructor.
* The only way to construct a coroutine is to pass it the routine
* it needs to run. The first argument of the function should be a
* reference to the Coroutine<Arg,Ret>::caller_type which the
* routine will use as a way for yielding to the caller.
* The optional second boolean argument controls if the Coroutine
* should be run on creation, which mimics Boost's Coroutine
* semantics by default. This can be disabled as an optimization to
* avoid unnecessary context switches on Coroutine creation.
*
* @param f task run by the coroutine
* @param run_coroutine set to false to disable running the coroutine
* immediately after it is created
*/
Coroutine(std::function<void(CallerType&)> f, bool run_coroutine = true)
: Fiber(), task(f), caller(*this)
{
// When desired, run the Coroutine after it is created
if (run_coroutine)
this->call();
}
virtual ~Coroutine() {}
public:
/** Coroutine interface */
/**
* operator() is the way we can jump inside the coroutine
* and passing arguments.
*
* This method is generated only if the coroutine takes
* arguments (Arg != void)
*/
template <typename T = Arg>
Coroutine&
operator()(typename std::enable_if<
!std::is_same<T, void>::value, T>::type param)
{
argsChannel.push(param);
this->call();
return *this;
}
/**
* operator() is the way we can jump inside the coroutine.
*
* This method is generated only if the coroutine takes
* no arguments. (Arg = void)
*/
template <typename T = Arg>
typename std::enable_if<std::is_same<T, void>::value, Coroutine>::type&
operator()()
{
this->call();
return *this;
}
/**
* get() is the way we can extrapolate return values
* (yielded) from the coroutine.
* The caller blocks, waiting for the value, unless it is already
* available; otherwise coroutine execution is resumed,
* and caller won't execute until a value is yielded back
* from the coroutine.
*
* @return ret yielded value
*/
template <typename T = Ret>
typename std::enable_if<!std::is_same<T, void>::value, T>::type
get()
{
auto& ret_channel = caller.retChannel;
while (ret_channel.empty()) {
this->call();
}
auto ret = ret_channel.top();
ret_channel.pop();
return ret;
}
/** Check if coroutine is still running */
operator bool() const { return !this->finished(); }
private:
/**
* Overriding base (Fiber) main.
* This method will be automatically called by the Fiber
* running engine and it is a simple wrapper for the task
* that the coroutine is supposed to run.
*/
void main() override { this->task(caller); }
void
call()
{
caller.callerFiber = currentFiber();
run();
}
private:
/** Arguments for the coroutine */
ArgChannel argsChannel;
/** Coroutine task */
std::function<void(CallerType&)> task;
/** Coroutine caller */
CallerType caller;
};
} //namespace m5
#endif // __BASE_COROUTINE_HH__