1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
/**
* 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 "null.h"
#include <exception>
#include <atomic>
#include <chrono>
#include <cstdint>
#include <cstring>
#include <functional>
#include <thread>
#include "althrd_setname.h"
#include "almalloc.h"
#include "core/device.h"
#include "core/helpers.h"
namespace {
using std::chrono::seconds;
using std::chrono::milliseconds;
using std::chrono::nanoseconds;
constexpr char nullDevice[] = "No Output";
struct NullBackend final : public BackendBase {
NullBackend(DeviceBase *device) noexcept : BackendBase{device} { }
int mixerProc();
void open(std::string_view name) override;
bool reset() override;
void 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)
{
mDevice->renderSamples(nullptr, mDevice->UpdateSize, 0u);
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(std::string_view name)
{
if(name.empty())
name = nullDevice;
else if(name != nullDevice)
throw al::backend_exception{al::backend_error::NoDevice, "Device name \"%.*s\" not found",
static_cast<int>(name.length()), name.data()};
mDevice->DeviceName = name;
}
bool NullBackend::reset()
{
setDefaultWFXChannelOrder();
return true;
}
void NullBackend::start()
{
try {
mKillNow.store(false, std::memory_order_release);
mThread = std::thread{std::mem_fn(&NullBackend::mixerProc), this};
}
catch(std::exception& e) {
throw al::backend_exception{al::backend_error::DeviceError,
"Failed to start mixing thread: %s", e.what()};
}
}
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); }
std::string NullBackendFactory::probe(BackendType type)
{
std::string outnames;
switch(type)
{
case BackendType::Playback:
/* Includes null char. */
outnames.append(nullDevice, sizeof(nullDevice));
break;
case BackendType::Capture:
break;
}
return outnames;
}
BackendPtr NullBackendFactory::createBackend(DeviceBase *device, BackendType type)
{
if(type == BackendType::Playback)
return BackendPtr{new NullBackend{device}};
return nullptr;
}
BackendFactory &NullBackendFactory::getFactory()
{
static NullBackendFactory factory{};
return factory;
}
|
