From e7494667adbb5c0a5264eb3872f83cc4099881ea Mon Sep 17 00:00:00 2001
From: Skyth <19259897+blueskythlikesclouds@users.noreply.github.com>
Date: Sun, 1 Dec 2024 13:55:50 +0300
Subject: [PATCH] Use readerwriterqueue for SDL2 audio.

---
 UnleashedRecomp/CMakeLists.txt             |  2 +
 UnleashedRecomp/apu/driver/sdl2_driver.cpp | 44 ++++++----------------
 UnleashedRecomp/stdafx.h                   |  1 +
 vcpkg.json                                 |  3 +-
 4 files changed, 17 insertions(+), 33 deletions(-)

diff --git a/UnleashedRecomp/CMakeLists.txt b/UnleashedRecomp/CMakeLists.txt
index f206680..6f0af6e 100644
--- a/UnleashedRecomp/CMakeLists.txt
+++ b/UnleashedRecomp/CMakeLists.txt
@@ -160,6 +160,7 @@ find_package(unofficial-concurrentqueue REQUIRED)
 find_package(imgui CONFIG REQUIRED)
 find_package(magic_enum CONFIG REQUIRED)
 find_package(unofficial-tiny-aes-c CONFIG REQUIRED)
+find_path(READERWRITERQUEUE_INCLUDE_DIRS "readerwriterqueue/atomicops.h")
 
 file(MAKE_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR}/D3D12)
 add_custom_command(TARGET UnleashedRecomp POST_BUILD
@@ -207,6 +208,7 @@ target_include_directories(UnleashedRecomp PRIVATE
     ${LIBMSPACK_PATH}
     ${Stb_INCLUDE_DIR}
     ${SMOLV_SOURCE_DIR}
+    ${READERWRITERQUEUE_INCLUDE_DIRS}
 )
 
 target_precompile_headers(UnleashedRecomp PUBLIC ${SWA_PRECOMPILED_HEADERS})
diff --git a/UnleashedRecomp/apu/driver/sdl2_driver.cpp b/UnleashedRecomp/apu/driver/sdl2_driver.cpp
index 87c7e2f..da4cba7 100644
--- a/UnleashedRecomp/apu/driver/sdl2_driver.cpp
+++ b/UnleashedRecomp/apu/driver/sdl2_driver.cpp
@@ -5,35 +5,22 @@
 #include <kernel/heap.h>
 
 #define SDLAUDIO_DRIVER_KEY (uint32_t)('SDLA')
-constexpr uint32_t g_semaphoreCount = 16;
-constexpr uint32_t g_audioFrameSize = XAUDIO_NUM_SAMPLES * XAUDIO_NUM_CHANNELS;
 
-PPCFunc* volatile g_clientCallback{};
-DWORD g_clientCallbackParam{}; // pointer in guest memory
+static constexpr uint32_t AUDIO_FRAME_SIZE = XAUDIO_NUM_SAMPLES * XAUDIO_NUM_CHANNELS;
 
-SDL_AudioDeviceID g_audioDevice{};
-SDL_sem* g_audioSemaphore{ SDL_CreateSemaphore(g_semaphoreCount) };
-uint32_t g_audioFrames[g_audioFrameSize * g_semaphoreCount];
-uint32_t g_audioFrameIndex = 0;
-uint32_t g_renderFrameIndex = 0; // Index of frame that's being rendered
-uint32_t g_numRenderFrames = 0; // Number of frames to render
-Mutex g_framesMutex{};
+static std::atomic<PPCFunc*> g_clientCallback{};
+static DWORD g_clientCallbackParam{}; // pointer in guest memory
+
+static SDL_AudioDeviceID g_audioDevice{};
+static moodycamel::BlockingReaderWriterCircularBuffer<std::array<uint32_t, AUDIO_FRAME_SIZE>> g_audioQueue(16);
 
 static void SDLAudioCallback(void*, uint8_t* frames, int len)
 {
-    std::lock_guard guard{ g_framesMutex };
-    if (g_numRenderFrames == 0)
-    {
-        memset(frames, 0, len);
-    }
+    std::array<uint32_t, AUDIO_FRAME_SIZE> audioFrame;
+    if (g_audioQueue.try_dequeue(audioFrame))
+        memcpy(frames, &audioFrame, sizeof(audioFrame));
     else
-    {
-        g_renderFrameIndex = (g_renderFrameIndex + 1) % g_semaphoreCount;
-        auto* srcFrames = &g_audioFrames[g_renderFrameIndex * g_audioFrameSize];
-        memcpy(frames, srcFrames, g_audioFrameSize * sizeof(float));
-        --g_numRenderFrames;
-    }
-    SDL_SemPost(g_audioSemaphore);
+        memset(frames, 0, len);
 }
 
 static PPC_FUNC(DriverLoop)
@@ -43,11 +30,8 @@ static PPC_FUNC(DriverLoop)
     while (true)
     {
         if (!g_clientCallback)
-        {
             continue;
-        }
 
-        SDL_SemWait(g_audioSemaphore);
         ctx.r3.u64 = g_clientCallbackParam;
         GuestCode::Run((void*)g_clientCallback, &ctx);
     }
@@ -55,8 +39,6 @@ static PPC_FUNC(DriverLoop)
 
 void XAudioInitializeSystem()
 {
-    assert(g_audioSemaphore);
-
     SDL_SetHint(SDL_HINT_AUDIO_CATEGORY, "playback");
     SDL_SetHint(SDL_HINT_AUDIO_DEVICE_APP_NAME, "SWA");
 
@@ -87,9 +69,7 @@ void XAudioRegisterClient(PPCFunc* callback, uint32_t param)
 
 void XAudioSubmitFrame(void* samples)
 {
-    std::lock_guard guard{ g_framesMutex };
-    uint32_t* audioFrame = &g_audioFrames[g_audioFrameSize * g_audioFrameIndex];
-    g_audioFrameIndex = (g_audioFrameIndex + 1) % g_semaphoreCount;
+    std::array<uint32_t, AUDIO_FRAME_SIZE> audioFrame;
 
     for (size_t i = 0; i < XAUDIO_NUM_SAMPLES; i++)
     {
@@ -97,5 +77,5 @@ void XAudioSubmitFrame(void* samples)
             audioFrame[i * XAUDIO_NUM_CHANNELS + j] = std::byteswap(((uint32_t*)samples)[j * XAUDIO_NUM_SAMPLES + i]);
     }
 
-    ++g_numRenderFrames;
+    g_audioQueue.wait_enqueue(audioFrame);
 }
diff --git a/UnleashedRecomp/stdafx.h b/UnleashedRecomp/stdafx.h
index 8fd5bb2..bf52446 100644
--- a/UnleashedRecomp/stdafx.h
+++ b/UnleashedRecomp/stdafx.h
@@ -32,6 +32,7 @@
 #include <wrl/client.h>
 #include <smolv.h>
 #include <print>
+#include <readerwriterqueue/readerwritercircularbuffer.h>
 
 using Microsoft::WRL::ComPtr;
 
diff --git a/vcpkg.json b/vcpkg.json
index e5db0fe..5e13523 100644
--- a/vcpkg.json
+++ b/vcpkg.json
@@ -21,6 +21,7 @@
             "name": "imgui",
             "features": [ "sdl2-binding" ]
         },
-        "magic-enum"
+        "magic-enum",
+        "readerwriterqueue"
     ]
 }