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/**
* 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 <exception>
#include <atomic>
#include <chrono>
#include <cstdint>
#include <cstring>
#include <functional>
#include <thread>
#include "alcmain.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();
ALCenum open(const ALCchar *name) override;
bool reset() override;
bool start() override;
void stop() override;
std::atomic<bool> 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<seconds>((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;
}
ALCenum NullBackend::open(const ALCchar *name)
{
if(!name)
name = nullDevice;
else if(strcmp(name, nullDevice) != 0)
return ALC_INVALID_VALUE;
mDevice->DeviceName = name;
return ALC_NO_ERROR;
}
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;
}
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