/** * OpenAL cross platform audio library * Copyright (C) 2010 by Chris Robinson * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Library General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This library 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 * Library General Public License for more details. * * You should have received a copy of the GNU Library General Public * License along with this library; if not, write to the * Free Software Foundation, Inc., * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. * Or go to http://www.gnu.org/copyleft/lgpl.html */ #include "config.h" #include "backends/null.h" #include #include #include #include #include #include #include #include "alcmain.h" #include "alexcpt.h" #include "almalloc.h" #include "alu.h" #include "logging.h" #include "threads.h" namespace { using std::chrono::seconds; using std::chrono::milliseconds; using std::chrono::nanoseconds; constexpr ALCchar nullDevice[] = "No Output"; struct NullBackend final : public BackendBase { NullBackend(ALCdevice *device) noexcept : BackendBase{device} { } int mixerProc(); void open(const ALCchar *name) override; bool reset() override; bool start() override; void stop() override; std::atomic mKillNow{true}; std::thread mThread; DEF_NEWDEL(NullBackend) }; int NullBackend::mixerProc() { const milliseconds restTime{mDevice->UpdateSize*1000/mDevice->Frequency / 2}; SetRTPriority(); althrd_setname(MIXER_THREAD_NAME); int64_t done{0}; auto start = std::chrono::steady_clock::now(); while(!mKillNow.load(std::memory_order_acquire) && mDevice->Connected.load(std::memory_order_acquire)) { auto now = std::chrono::steady_clock::now(); /* This converts from nanoseconds to nanosamples, then to samples. */ int64_t avail{std::chrono::duration_cast((now-start) * mDevice->Frequency).count()}; if(avail-done < mDevice->UpdateSize) { std::this_thread::sleep_for(restTime); continue; } while(avail-done >= mDevice->UpdateSize) { lock(); aluMixData(mDevice, nullptr, mDevice->UpdateSize); unlock(); done += mDevice->UpdateSize; } /* For every completed second, increment the start time and reduce the * samples done. This prevents the difference between the start time * and current time from growing too large, while maintaining the * correct number of samples to render. */ if(done >= mDevice->Frequency) { seconds s{done/mDevice->Frequency}; start += s; done -= mDevice->Frequency*s.count(); } } return 0; } void NullBackend::open(const ALCchar *name) { if(!name) name = nullDevice; else if(strcmp(name, nullDevice) != 0) throw al::backend_exception{ALC_INVALID_VALUE, "Device name \"%s\" not found", name}; mDevice->DeviceName = name; } bool NullBackend::reset() { SetDefaultWFXChannelOrder(mDevice); return true; } bool NullBackend::start() { try { mKillNow.store(false, std::memory_order_release); mThread = std::thread{std::mem_fn(&NullBackend::mixerProc), this}; return true; } catch(std::exception& e) { ERR("Failed to start mixing thread: %s\n", e.what()); } catch(...) { } return false; } void NullBackend::stop() { if(mKillNow.exchange(true, std::memory_order_acq_rel) || !mThread.joinable()) return; mThread.join(); } } // namespace bool NullBackendFactory::init() { return true; } bool NullBackendFactory::querySupport(BackendType type) { return (type == BackendType::Playback); } void NullBackendFactory::probe(DevProbe type, std::string *outnames) { switch(type) { case DevProbe::Playback: /* Includes null char. */ outnames->append(nullDevice, sizeof(nullDevice)); break; case DevProbe::Capture: break; } } BackendPtr NullBackendFactory::createBackend(ALCdevice *device, BackendType type) { if(type == BackendType::Playback) return BackendPtr{new NullBackend{device}}; return nullptr; } BackendFactory &NullBackendFactory::getFactory() { static NullBackendFactory factory{}; return factory; }