audio: replace open-coded buffer arithmetic

Replace open-coded buffer arithmetic with the new function
audio_ring_posb(). That's the position in backward direction
of a given point at a given distance.

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Reviewed-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Message-Id: <20220301191311.26695-1-vr_qemu@t-online.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/audio/audio_int.h b/audio/audio_int.h
index 428a091d05..71be162271 100644
--- a/audio/audio_int.h
+++ b/audio/audio_int.h
@@ -266,6 +266,19 @@ static inline size_t audio_ring_dist(size_t dst, size_t src, size_t len)
     return (dst >= src) ? (dst - src) : (len - src + dst);
 }
 
+/**
+ * audio_ring_posb() - returns new position in ringbuffer in backward
+ * direction at given distance
+ *
+ * @pos: current position in ringbuffer
+ * @dist: distance in ringbuffer to walk in reverse direction
+ * @len: size of ringbuffer
+ */
+static inline size_t audio_ring_posb(size_t pos, size_t dist, size_t len)
+{
+    return pos >= dist ? pos - dist : len - dist + pos;
+}
+
 #define dolog(fmt, ...) AUD_log(AUDIO_CAP, fmt, ## __VA_ARGS__)
 
 #ifdef DEBUG