eab477370f
Libc components cannot use regular calls to select() as this may suspend their execution. In this case incoming RPCs will be deferred until select() returns and the component returns to the entrypoint dispatch loop. The Libc::Signal_handler solves this problem with a its select() that either returns the currently ready file descriptors immediately or calls the registered handler function during libc resume.
68 lines
1.7 KiB
C++
68 lines
1.7 KiB
C++
/*
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* \brief Support for handling select() in LibC components
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* \author Christian Helmuth
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* \date 2017-02-13
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*/
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/*
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* Copyright (C) 2017 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__LIBC__SELECT_H_
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#define _INCLUDE__LIBC__SELECT_H_
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/* Libc includes */
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#include <sys/select.h> /* for fd_set */
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namespace Libc {
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struct Select_cb;
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typedef Genode::Constructible<Libc::Select_cb> Select_handler_cb;
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struct Select_handler_base
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{
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Select_handler_cb *_select_cb;
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Select_handler_base();
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~Select_handler_base();
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/**
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* Traditional select()
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*
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* \returns 0 if no descriptor was ready and schedules for later call
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* of select_ready(), or number of currently ready file
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* descriptors. The latter case does not schedule
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* select_ready().
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*/
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int select(int nfds, fd_set &readfds, fd_set &writefds, fd_set &exceptfds);
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virtual void select_ready(int nready, fd_set const &, fd_set const &, fd_set const &) = 0;
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/* \noapi */
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void dispatch_select();
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};
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template <typename T>
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struct Select_handler : Select_handler_base
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{
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T &obj;
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void (T::*member) (int, fd_set const &, fd_set const &, fd_set const &);
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Select_handler(T &obj,
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void (T::*member)(int, fd_set const &, fd_set const &, fd_set const &))
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: obj(obj), member(member) { }
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void select_ready(int nready, fd_set const &readfds,
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fd_set const &writefds, fd_set const &exceptfds) override
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{
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(obj.*member)(nready, readfds, writefds, exceptfds);
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}
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};
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}
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#endif /* _INCLUDE__LIBC__SELECT_H_ */
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