AudioServer: Add a buffer queue so we can buffer some sound.

The idea here is to keep a small number of sample buffers queued in the
AudioServer so we don't get caught without something to play.

Libraries/LibAudio/AClientConnection.cpp

@@ -25,3 +25,18 @@ void AClientConnection::play(const ABuffer& buffer, bool block)
  request.play_buffer.buffer_id = buffer.shared_buffer_id();
  sync_request(request, block ? ASAPI_ServerMessage::Type::FinishedPlayingBuffer : ASAPI_ServerMessage::Type::PlayingBuffer);
 }
+
+void AClientConnection::enqueue(const ABuffer& buffer)
+{
+ for (;;) {
+ const_cast<ABuffer&>(buffer).shared_buffer().share_with(server_pid());
+ ASAPI_ClientMessage request;
+ request.type = ASAPI_ClientMessage::Type::EnqueueBuffer;
+ request.play_buffer.buffer_id = buffer.shared_buffer_id();
+ auto response = sync_request(request, ASAPI_ServerMessage::Type::EnqueueBufferResponse);
+ if (response.success)
+ break;
+ dbg() << "EnqueueBuffer failed, retrying...";
+ sleep(1);
+ }
+}

Libraries/LibAudio/AClientConnection.h

@@ -12,4 +12,5 @@ class AClientConnection : public IPC::Client::Connection<ASAPI_ServerMessage, AS
 
  virtual void handshake() override;
  void play(const ABuffer&, bool block);
+ void enqueue(const ABuffer&);
 };

Libraries/LibAudio/ASAPI.h

@@ -6,10 +6,12 @@ struct ASAPI_ServerMessage {
  Greeting,
  PlayingBuffer,
  FinishedPlayingBuffer,
+ EnqueueBufferResponse,
  };
 
  Type type { Type::Invalid };
  unsigned extra_size { 0 };
+ bool success { true };
 
  union {
  struct {
@@ -27,6 +29,7 @@ struct ASAPI_ClientMessage {
  Invalid,
  Greeting,
  PlayBuffer,
+ EnqueueBuffer,
  };
 
  Type type { Type::Invalid };

Servers/AudioServer/ASClientConnection.cpp

@@ -54,6 +54,30 @@ bool ASClientConnection::handle_message(const ASAPI_ClientMessage& message, cons
  m_mixer.queue(*this, ABuffer::create_with_shared_buffer(*shared_buffer));
  break;
  }
+ case ASAPI_ClientMessage::Type::EnqueueBuffer: {
+ auto shared_buffer = SharedBuffer::create_from_shared_buffer_id(message.play_buffer.buffer_id);
+ if (!shared_buffer) {
+ did_misbehave();
+ return false;
+ }
+
+ static const int max_in_queue = 2;
+
+ ASAPI_ServerMessage reply;
+ reply.type = ASAPI_ServerMessage::Type::EnqueueBufferResponse;
+ reply.playing_buffer.buffer_id = message.play_buffer.buffer_id;
+ if (m_buffer_queue.size() >= max_in_queue) {
+ reply.success = false;
+ } else {
+ m_buffer_queue.enqueue(ABuffer::create_with_shared_buffer(*shared_buffer));
+ }
+ post_message(reply);
+
+ if (m_playing_queued_buffer_id == -1)
+ play_next_in_queue();
+
+ break;
+ }
  case ASAPI_ClientMessage::Type::Invalid:
  default:
  dbgprintf("ASClientConnection: Unexpected message ID %d\n", int(message.type));
@@ -65,8 +89,19 @@ bool ASClientConnection::handle_message(const ASAPI_ClientMessage& message, cons
 
 void ASClientConnection::did_finish_playing_buffer(Badge<ASMixer>, int buffer_id)
 {
+ if (m_playing_queued_buffer_id == buffer_id)
+ play_next_in_queue();
+
  ASAPI_ServerMessage reply;
  reply.type = ASAPI_ServerMessage::Type::FinishedPlayingBuffer;
  reply.playing_buffer.buffer_id = buffer_id;
  post_message(reply);
 }
+
+void ASClientConnection::play_next_in_queue()
+{
+ dbg() << "Playing next in queue (" << m_buffer_queue.size() << " queued)";
+ auto buffer = m_buffer_queue.dequeue();
+ m_playing_queued_buffer_id = buffer->shared_buffer_id();
+ m_mixer.queue(*this, move(buffer));
+}

Servers/AudioServer/ASClientConnection.h

@@ -1,8 +1,10 @@
 #pragma once
 
+#include <AK/Queue.h>
 #include <LibAudio/ASAPI.h>
 #include <LibCore/CoreIPCServer.h>
 
+class ABuffer;
 class ASMixer;
 
 class ASClientConnection final : public IPC::Server::Connection<ASAPI_ServerMessage, ASAPI_ClientMessage> {
@@ -16,5 +18,9 @@ class ASClientConnection final : public IPC::Server::Connection<ASAPI_ServerMess
  void did_finish_playing_buffer(Badge<ASMixer>, int buffer_id);
 
 private:
+ void play_next_in_queue();
+
  ASMixer& m_mixer;
+ Queue<NonnullRefPtr<ABuffer>> m_buffer_queue;
+ int m_playing_queued_buffer_id { -1 };
 };

Userland/aplay.cpp

@@ -25,7 +25,7 @@ int main(int argc, char **argv)
  break;
  }
  printf("Playing %d sample(s)\n", samples->sample_count());
- a_conn.play(*samples, true);
+ a_conn.enqueue(*samples);
  }
 
  printf("Exiting! :)\n");