From 9acb513fde8c9f4f205c4796aacd562a736f01dd Mon Sep 17 00:00:00 2001
From: Alula <julekonopinska@gmail.com>
Date: Sun, 20 Sep 2020 17:37:53 +0200
Subject: [PATCH] fix integer overflow handling in sample mixer

---
 src/sound/mod.rs | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/sound/mod.rs b/src/sound/mod.rs
index 2148adb..42f11b4 100644
--- a/src/sound/mod.rs
+++ b/src/sound/mod.rs
@@ -13,6 +13,7 @@ use crate::sound::pixtone::PixTonePlayback;
 use crate::sound::playback::{PlaybackEngine, SavedPlaybackState};
 use crate::sound::wave_bank::SoundBank;
 use crate::str;
+use num_traits::clamp;
 
 mod wave_bank;
 mod organya;
@@ -266,7 +267,7 @@ fn run<T>(rx: Receiver<PlaybackMessage>, bank: SoundBank,
                         (sample & 0xff) << 8
                     }
                 };
-                let pxt_sample: u16 = pxt_buf[pxt_index] ^ 0x8000;
+                let pxt_sample: u16 = pxt_buf[pxt_index];
 
                 if pxt_index < (pxt_buf.len() - 1) {
                     pxt_index += 1;
@@ -276,7 +277,10 @@ fn run<T>(rx: Receiver<PlaybackMessage>, bank: SoundBank,
                     pixtone.mix(&mut pxt_buf, sample_rate / speed);
                 }
 
-                let sample = org_sample.wrapping_add(pxt_sample);
+                let sample = clamp(
+                    (((org_sample ^ 0x8000) as i16) as isize)
+                        + (((pxt_sample ^ 0x8000) as i16) as isize)
+                    , -0x7fff, 0x7fff) as u16 ^ 0x8000;
 
                 let value: T = Sample::from::<u16>(&sample);
                 for sample in frame.iter_mut() {