CDROM: Implement asynchronous disc reading

src/core/cdrom_async_reader.cpp

@@ -0,0 +1,162 @@
+#include "cdrom_async_reader.h"
+#include "common/assert.h"
+#include "common/log.h"
+#include "common/timer.h"
+Log_SetChannel(CDROMAsyncReader);
+
+CDROMAsyncReader::CDROMAsyncReader() = default;
+
+CDROMAsyncReader::~CDROMAsyncReader()
+{
+  StopThread();
+}
+
+void CDROMAsyncReader::StartThread()
+{
+  if (IsUsingThread())
+    return;
+
+  m_shutdown_flag.store(false);
+  m_read_thread = std::thread(&CDROMAsyncReader::WorkerThreadEntryPoint, this);
+}
+
+void CDROMAsyncReader::StopThread()
+{
+  if (!IsUsingThread())
+    return;
+
+  {
+    std::unique_lock<std::mutex> lock(m_mutex);
+    if (m_sector_read_pending.load())
+      m_notify_read_complete_cv.wait(lock, [this]() { return !m_sector_read_pending.load(); });
+
+    m_shutdown_flag.store(true);
+    m_do_read_cv.notify_one();
+  }
+
+  m_read_thread.join();
+}
+
+void CDROMAsyncReader::SetMedia(std::unique_ptr<CDImage> media)
+{
+  WaitForReadToComplete();
+  m_media = std::move(media);
+}
+
+void CDROMAsyncReader::RemoveMedia()
+{
+  WaitForReadToComplete();
+  m_media.reset();
+}
+
+void CDROMAsyncReader::QueueReadSector(CDImage::LBA lba)
+{
+  if (!IsUsingThread())
+  {
+    m_sector_read_pending.store(true);
+    m_next_position_set.store(true);
+    m_next_position = lba;
+    DoSectorRead();
+    return;
+  }
+
+  std::unique_lock<std::mutex> lock(m_mutex);
+  if (m_sector_read_pending.load())
+    m_notify_read_complete_cv.wait(lock, [this]() { return !m_sector_read_pending.load(); });
+
+  // don't re-read the same sector if it was the last one we read
+  // the CDC code does this when seeking->reading
+  if (m_last_read_sector == lba && m_sector_read_result.load())
+  {
+    Log_DebugPrintf("Skipping re-reading same sector %u", lba);
+    return;
+  }
+
+  m_sector_read_pending.store(true);
+  m_next_position_set.store(true);
+  m_next_position = lba;
+  m_do_read_cv.notify_one();
+}
+
+void CDROMAsyncReader::QueueReadNextSector()
+{
+  if (!IsUsingThread())
+  {
+    m_sector_read_pending.store(true);
+    DoSectorRead();
+    return;
+  }
+
+  std::unique_lock<std::mutex> lock(m_mutex);
+  if (m_sector_read_pending.load())
+    m_notify_read_complete_cv.wait(lock, [this]() { return !m_sector_read_pending.load(); });
+
+  m_sector_read_pending.store(true);
+  m_do_read_cv.notify_one();
+}
+
+bool CDROMAsyncReader::WaitForReadToComplete()
+{
+  if (!IsUsingThread())
+    return m_sector_read_result.load();
+
+  std::unique_lock<std::mutex> lock(m_mutex);
+  if (m_sector_read_pending.load())
+  {
+    Log_DebugPrintf("Sector read pending, waiting");
+    m_notify_read_complete_cv.wait(lock, [this]() { return !m_sector_read_pending.load(); });
+  }
+
+  return m_sector_read_result.load();
+}
+
+void CDROMAsyncReader::DoSectorRead()
+{
+#ifdef _DEBUG
+  Common::Timer timer;
+#endif
+
+  if (m_next_position_set.load())
+  {
+    if (m_media->GetPositionOnDisc() != m_next_position && !m_media->Seek(m_next_position))
+    {
+      Log_WarningPrintf("Seek to LBA %u failed", m_next_position);
+      m_sector_read_result.store(false);
+      return;
+    }
+  }
+
+  CDImage::LBA pos = m_media->GetPositionOnDisc();
+  if (!m_media->ReadSubChannelQ(&m_subq) || !m_media->ReadRawSector(m_sector_buffer.data()))
+  {
+    m_sector_read_result.store(false);
+    Log_WarningPrintf("Read of LBA %u failed", pos);
+    return;
+  }
+
+  m_last_read_sector = pos;
+  m_sector_read_result.store(true);
+
+#ifdef _DEBUG
+  if (timer.GetTimeMilliseconds() > 1.0f)
+    Log_WarningPrintf("Read LBA %u took %.2f msec", pos, timer.GetTimeMilliseconds());
+#endif
+}
+
+void CDROMAsyncReader::WorkerThreadEntryPoint()
+{
+  std::unique_lock lock(m_mutex);
+
+  while (!m_shutdown_flag.load())
+  {
+    m_do_read_cv.wait(lock, [this]() { return (m_shutdown_flag.load() || m_sector_read_pending.load()); });
+    if (m_sector_read_pending.load())
+    {
+      lock.unlock();
+      DoSectorRead();
+      lock.lock();
+      m_sector_read_pending.store(false);
+      m_notify_read_complete_cv.notify_one();
+    }
+  }
+}