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/* RPC call and callback templates
Copyright (C) 2014-2021 Free Software Foundation, Inc.
This file is part of GCC.
GCC 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 3, or (at your option) any later
version.
GCC 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 GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#ifndef CC1_PLUGIN_RPC_HH
#define CC1_PLUGIN_RPC_HH
#include "status.hh"
#include "connection.hh"
#include "deleter.hh"
namespace cc1_plugin
{
// The plugin API may contain some "const" method parameters.
// However, when unmarshalling we cannot unmarshall into a const
// object; and furthermore we want to be able to deallocate pointers
// when finished with them. This wrapper class lets us properly
// remove the "const" and handle deallocation from pointer types.
template<typename T>
class argument_wrapper
{
public:
argument_wrapper () { }
~argument_wrapper () { }
argument_wrapper (const argument_wrapper &) = delete;
argument_wrapper &operator= (const argument_wrapper &) = delete;
T get () const { return m_object; }
status unmarshall (connection *conn)
{
return ::cc1_plugin::unmarshall (conn, &m_object);
}
private:
T m_object;
};
// Specialization for any kind of pointer.
template<typename T>
class argument_wrapper<T *>
{
public:
argument_wrapper () = default;
~argument_wrapper () = default;
argument_wrapper (const argument_wrapper &) = delete;
argument_wrapper &operator= (const argument_wrapper &) = delete;
typedef typename std::remove_const<T>::type type;
const type *get () const
{
return m_object.get ();
}
status unmarshall (connection *conn)
{
type *ptr;
if (!::cc1_plugin::unmarshall (conn, &ptr))
return FAIL;
m_object.reset (ptr);
return OK;
}
private:
unique_ptr<type> m_object;
};
// There are two kinds of template functions here: "call" and
// "invoker".
// The "call" template is used for making a remote procedure call.
// It starts a query ('Q') packet, marshalls its arguments, waits
// for a result, and finally reads and returns the result via an
// "out" parameter.
// The "invoker" template is used when receiving a remote procedure
// call. This template function is suitable for use with the
// "callbacks" and "connection" classes. It decodes incoming
// arguments, passes them to the wrapped function, and finally
// marshalls a reply packet.
template<typename R, typename... Arg>
status
call (connection *conn, const char *method, R *result, Arg... args)
{
if (!conn->send ('Q'))
return FAIL;
if (!marshall (conn, method))
return FAIL;
if (!marshall (conn, (int) sizeof... (Arg)))
return FAIL;
if (!marshall (conn, args...))
return FAIL;
if (!conn->wait_for_result ())
return FAIL;
if (!unmarshall (conn, result))
return FAIL;
return OK;
}
// The base case -- just return OK.
template<int I, typename... T>
typename std::enable_if<I == sizeof... (T), status>::type
unmarshall (connection *, std::tuple<T...> &)
{
return OK;
}
// Unmarshall this argument, then unmarshall all subsequent args.
template<int I, typename... T>
typename std::enable_if<I < sizeof... (T), status>::type
unmarshall (connection *conn, std::tuple<T...> &value)
{
if (!std::get<I> (value).unmarshall (conn))
return FAIL;
return unmarshall<I + 1, T...> (conn, value);
}
// Wrap a static function that is suitable for use as a callback.
// This is a template function inside a template class to work
// around limitations with multiple variadic packs.
template<typename R, typename... Arg>
class invoker
{
// Base case -- we can call the function.
template<int I, R func (connection *, Arg...), typename... T>
static typename std::enable_if<I == sizeof... (Arg), R>::type
call (connection *conn, const std::tuple<argument_wrapper<Arg>...> &,
T... args)
{
return func (conn, args...);
}
// Unpack one argument and continue the recursion.
template<int I, R func (connection *, Arg...), typename... T>
static typename std::enable_if<I < sizeof... (Arg), R>::type
call (connection *conn, const std::tuple<argument_wrapper<Arg>...> &value,
T... args)
{
return call<I + 1, func> (conn, value, args...,
std::get<I> (value).get ());
}
public:
// A callback function that reads arguments from the connection,
// calls the wrapped function, and then sends the result back on
// the connection.
template<R func (connection *, Arg...)>
static status
invoke (connection *conn)
{
if (!unmarshall_check (conn, sizeof... (Arg)))
return FAIL;
std::tuple<argument_wrapper<Arg>...> wrapped;
if (!unmarshall<0> (conn, wrapped))
return FAIL;
R result = call<0, func> (conn, wrapped);
if (!conn->send ('R'))
return FAIL;
return marshall (conn, result);
}
};
};
#endif // CC1_PLUGIN_RPC_HH
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