1 files changed, 62 insertions, 0 deletions
diff --git a/alc/backends/base.cpp b/alc/backends/base.cpp
new file mode 100644
index 00000000..25531cf5
--- /dev/null
+++ b/alc/backends/base.cpp
@@ -0,0 +1,62 @@
+
+#include "config.h"
+
+#include "base.h"
+
+#include <atomic>
+#include <thread>
+
+#include "AL/al.h"
+
+#include "alcmain.h"
+#include "alexcpt.h"
+#include "alnumeric.h"
+#include "atomic.h"
+
+
+ClockLatency GetClockLatency(ALCdevice *device)
+{
+    BackendBase *backend{device->Backend.get()};
+    ClockLatency ret{backend->getClockLatency()};
+    ret.Latency += device->FixedLatency;
+    return ret;
+}
+
+
+/* BackendBase method implementations. */
+BackendBase::BackendBase(ALCdevice *device) noexcept : mDevice{device}
+{ }
+
+BackendBase::~BackendBase() = default;
+
+bool BackendBase::reset()
+{ throw al::backend_exception{ALC_INVALID_DEVICE, "Invalid BackendBase call"}; }
+
+ALCenum BackendBase::captureSamples(al::byte*, ALCuint)
+{ return ALC_INVALID_DEVICE; }
+
+ALCuint BackendBase::availableSamples()
+{ return 0; }
+
+ClockLatency BackendBase::getClockLatency()
+{
+    ClockLatency ret;
+
+    ALuint refcount;
+    do {
+        while(((refcount=ReadRef(mDevice->MixCount))&1) != 0)
+            std::this_thread::yield();
+        ret.ClockTime = GetDeviceClockTime(mDevice);
+        std::atomic_thread_fence(std::memory_order_acquire);
+    } while(refcount != ReadRef(mDevice->MixCount));
+
+    /* NOTE: The device will generally have about all but one periods filled at
+     * any given time during playback. Without a more accurate measurement from
+     * the output, this is an okay approximation.
+     */
+    ret.Latency = std::max(std::chrono::seconds{mDevice->BufferSize-mDevice->UpdateSize},
+        std::chrono::seconds::zero());
+    ret.Latency /= mDevice->Frequency;
+
+    return ret;
+}