alc/backends/base.cpp

   1
   2 #include "config.h"
   3
   4 #include "base.h"
   5
   6 #include <atomic>
   7 #include <thread>
   8
   9 #include "AL/al.h"
  10
  11 #include "alcmain.h"
  12 #include "alnumeric.h"
  13 #include "atomic.h"
  14
  15
  16 ClockLatency GetClockLatency(ALCdevice *device)
  17 {
  18     BackendBase *backend{device->Backend.get()};
  19     ClockLatency ret{backend->getClockLatency()};
  20     ret.Latency += device->FixedLatency;
  21     return ret;
  22 }
  23
  24
  25 /* BackendBase method implementations. */
  26 BackendBase::BackendBase(ALCdevice *device) noexcept : mDevice{device}
  27 { }
  28
  29 BackendBase::~BackendBase() = default;
  30
  31 bool BackendBase::reset()
  32 { return false; }
  33
  34 ALCenum BackendBase::captureSamples(al::byte*, ALCuint)
  35 { return ALC_INVALID_DEVICE; }
  36
  37 ALCuint BackendBase::availableSamples()
  38 { return 0; }
  39
  40 ClockLatency BackendBase::getClockLatency()
  41 {
  42     ClockLatency ret;
  43
  44     ALuint refcount;
  45     do {
  46         while(((refcount=ReadRef(mDevice->MixCount))&1) != 0)
  47             std::this_thread::yield();
  48         ret.ClockTime = GetDeviceClockTime(mDevice);
  49         std::atomic_thread_fence(std::memory_order_acquire);
  50     } while(refcount != ReadRef(mDevice->MixCount));
  51
  52     /* NOTE: The device will generally have about all but one periods filled at
  53      * any given time during playback. Without a more accurate measurement from
  54      * the output, this is an okay approximation.
  55      */
  56     ret.Latency = std::max(std::chrono::seconds{mDevice->BufferSize-mDevice->UpdateSize},
  57         std::chrono::seconds::zero());
  58     ret.Latency /= mDevice->Frequency;
  59
  60     return ret;
  61 }