From e7d73e8493b3c66c561cace94b43e21e75c405fe Mon Sep 17 00:00:00 2001
From: Kp <kp@valhallalegends.com>
Date: Sat, 13 May 2023 15:02:55 +0000
Subject: [PATCH] Use RAII to manage SDL_LockAudio state

---
 common/main/d_sdl_audio.h       | 26 ++++++++++++++++++++++++++
 d2x-rebirth/libmve/mveplay.cpp  |  9 ++++-----
 similar/arch/sdl/digi_audio.cpp |  9 +++------
 similar/arch/sdl/digi_mixer.cpp |  1 -
 4 files changed, 33 insertions(+), 12 deletions(-)
 create mode 100644 common/main/d_sdl_audio.h

diff --git a/common/main/d_sdl_audio.h b/common/main/d_sdl_audio.h
new file mode 100644
index 000000000..fd1d070f3
--- /dev/null
+++ b/common/main/d_sdl_audio.h
@@ -0,0 +1,26 @@
+/*
+ * Portions of this file are copyright Rebirth contributors and licensed as
+ * described in COPYING.txt.
+ * See COPYING.txt for license details.
+ */
+
+#pragma once
+#include <SDL_audio.h>
+
+namespace dcx {
+
+struct RAII_SDL_LockAudio
+{
+	RAII_SDL_LockAudio()
+	{
+		SDL_LockAudio();
+	}
+	~RAII_SDL_LockAudio()
+	{
+		SDL_UnlockAudio();
+	}
+	RAII_SDL_LockAudio(const RAII_SDL_LockAudio &) = delete;
+	RAII_SDL_LockAudio &operator=(const RAII_SDL_LockAudio &) = delete;
+};
+
+}
diff --git a/d2x-rebirth/libmve/mveplay.cpp b/d2x-rebirth/libmve/mveplay.cpp
index f7ee76875..f43c927bd 100644
--- a/d2x-rebirth/libmve/mveplay.cpp
+++ b/d2x-rebirth/libmve/mveplay.cpp
@@ -33,6 +33,7 @@
 #endif
 
 #include "config.h"
+#include "d_sdl_audio.h"
 #include "mvelib.h"
 #include "mve_audio.h"
 #include "byteutil.h"
@@ -409,8 +410,9 @@ int MVESTREAM::handle_mve_segment_audioframedata(const mve_opcode major, const u
 	static const int selected_chan=1;
 	if (mve_audio_spec)
 	{
-		if (mve_audio_playing)
-			SDL_LockAudio();
+		std::optional<RAII_SDL_LockAudio> lock_audio{
+			mve_audio_playing ? std::optional<RAII_SDL_LockAudio>(std::in_place) : std::nullopt
+		};
 
 		const auto chan = get_ushort(data + 2);
 		unsigned nsamp = get_ushort(data + 4);
@@ -500,9 +502,6 @@ int MVESTREAM::handle_mve_segment_audioframedata(const mve_opcode major, const u
 			if (mve_audio_buftail == mve_audio_bufhead)
 				con_printf(CON_CRITICAL, "d'oh!  buffer ring overrun (%d)", mve_audio_bufhead);
 		}
-
-		if (mve_audio_playing)
-			SDL_UnlockAudio();
 	}
 
 	return 1;
diff --git a/similar/arch/sdl/digi_audio.cpp b/similar/arch/sdl/digi_audio.cpp
index 29f46e034..1ad23d491 100644
--- a/similar/arch/sdl/digi_audio.cpp
+++ b/similar/arch/sdl/digi_audio.cpp
@@ -26,6 +26,7 @@
 #include "piggy.h"
 
 #include "compiler-range_for.h"
+#include "d_sdl_audio.h"
 #include "d_underlying_value.h"
 
 namespace dcx {
@@ -147,7 +148,7 @@ static void audio_mixcallback(void *, Uint8 *stream, int len)
 
 	memset(stream, 0x80, len); // fix "static" sound bug on Mac OS X
 
-	SDL_LockAudio();
+	RAII_SDL_LockAudio lock_audio{};
 
 	range_for (auto &sl, SoundSlots)
 	{
@@ -184,8 +185,6 @@ static void audio_mixcallback(void *, Uint8 *stream, int len)
 			sl.position = std::distance(sl.samples.begin(), sldata);
 		}
 	}
-
-	SDL_UnlockAudio();
 }
 
 }
@@ -256,7 +255,7 @@ sound_channel digi_audio_start_sound(short soundnum, fix volume, sound_pan pan,
 	if (soundnum < 0)
 		return sound_channel::None;
 
-	SDL_LockAudio();
+	RAII_SDL_LockAudio lock_audio{};
 
 	const auto starting_channel = next_channel;
 
@@ -271,7 +270,6 @@ sound_channel digi_audio_start_sound(short soundnum, fix volume, sound_pan pan,
 		next_channel = next(next_channel);
 		if (next_channel == starting_channel)
 		{
-			SDL_UnlockAudio();
 			return sound_channel::None;
 		}
 	}
@@ -304,7 +302,6 @@ sound_channel digi_audio_start_sound(short soundnum, fix volume, sound_pan pan,
 
 	const auto i = next_channel;
 	next_channel = next(next_channel);
-	SDL_UnlockAudio();
 
 	return i;
 }
diff --git a/similar/arch/sdl/digi_mixer.cpp b/similar/arch/sdl/digi_mixer.cpp
index bfb4337a6..fb4e024c4 100644
--- a/similar/arch/sdl/digi_mixer.cpp
+++ b/similar/arch/sdl/digi_mixer.cpp
@@ -21,7 +21,6 @@
 #include <string.h>
 
 #include <SDL.h>
-#include <SDL_audio.h>
 #include <SDL_mixer.h>
 
 #include "pstypes.h"