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This patch introduces a publish/subscribe mechanism, allowing for loosely-coupled senders and receivers, with strongly-typed messages passing between them. For example, a GCC subsystem could publish messages about events, and a plugin could subscribe to them. An example can be seen in the selftests. gcc/ChangeLog: * Makefile.in (OBJS-libcommon): Add pub-sub.o. * pub-sub.cc: New file. * pub-sub.h: New file. * selftest-run-tests.cc (selftest::run_tests): Call selftest::pub_sub_cc_tests. * selftest.h (selftest::pub_sub_cc_tests): New decl. Signed-off-by: David Malcolm <dmalcolm@redhat.com>
139 lines
3.3 KiB
C++
139 lines
3.3 KiB
C++
/* Loosely-coupled notifications via the Publish-Subscribe pattern.
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Copyright (C) 2025 Free Software Foundation, Inc.
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Contributed by David Malcolm <dmalcolm@redhat.com>.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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#define INCLUDE_LIST
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#define INCLUDE_STRING
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "pub-sub.h"
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#if CHECKING_P
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#include "selftest.h"
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namespace selftest {
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/* Selftests. */
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// A topic for use in selftests
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namespace snafu {
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struct paper_jam {};
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struct out_of_paper
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{
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int tray;
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};
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struct ink_low
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{
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std::string color;
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};
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struct subscriber
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{
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virtual void on_message (const paper_jam &m) = 0;
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virtual void on_message (const out_of_paper &m) = 0;
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virtual void on_message (const ink_low &m) = 0;
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};
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} // namespace snafu
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static void
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test_example ()
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{
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struct logger : public snafu::subscriber
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{
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void on_message (const snafu::paper_jam &) final override
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{
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m_log += "paper jam\n";
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}
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void on_message (const snafu::out_of_paper &m) final override
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{
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m_log += "out of paper (tray " + std::to_string (m.tray) + ")\n";
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}
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void on_message (const snafu::ink_low &m) final override
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{
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m_log += "ink low: " + m.color + "\n";
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}
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std::string m_log;
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};
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pub_sub::channel<snafu::subscriber> printer_a;
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pub_sub::channel<snafu::subscriber> printer_b;
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pub_sub::channel<snafu::subscriber> printer_c;
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// No subscribers yet
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ASSERT_EQ (printer_a.get_if_active (), nullptr);
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ASSERT_EQ (printer_b.get_if_active (), nullptr);
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ASSERT_EQ (printer_c.get_if_active (), nullptr);
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// Subscribers to individual channels
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logger log_a;
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logger log_b;
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logger log_c;
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printer_a.add_subscriber (log_a);
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printer_b.add_subscriber (log_b);
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printer_c.add_subscriber (log_c);
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// A subscriber to all channels
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logger log_all;
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printer_a.add_subscriber (log_all);
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printer_b.add_subscriber (log_all);
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printer_c.add_subscriber (log_all);
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// The channels now have subscribers
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ASSERT_EQ (printer_a.get_if_active (), &printer_a);
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ASSERT_EQ (printer_b.get_if_active (), &printer_b);
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ASSERT_EQ (printer_c.get_if_active (), &printer_c);
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// Publish a message to each channel
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printer_a.publish (snafu::paper_jam {});
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printer_b.publish (snafu::out_of_paper {1});
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printer_c.publish (snafu::ink_low {"cyan"});
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// Verify that the subscribers got the messages they were meant to
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ASSERT_EQ (log_a.m_log, "paper jam\n");
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ASSERT_EQ (log_b.m_log, "out of paper (tray 1)\n");
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ASSERT_EQ (log_c.m_log, "ink low: cyan\n");
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ASSERT_EQ (log_all.m_log,
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"paper jam\n"
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"out of paper (tray 1)\n"
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"ink low: cyan\n");
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}
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/* Run all of the selftests within this file. */
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void
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pub_sub_cc_tests ()
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{
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test_example ();
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}
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} // namespace selftest
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#endif /* #if CHECKING_P */
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