I took time to understand these functions in the context of the rest of the code, which would have been a lot quicker with a comment like this. --- src/pcm/pcm_local.h | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+)
diff --git a/src/pcm/pcm_local.h b/src/pcm/pcm_local.h index cf018fc0..aae58ed3 100644 --- a/src/pcm/pcm_local.h +++ b/src/pcm/pcm_local.h @@ -480,6 +480,13 @@ static inline int snd_pcm_check_error(snd_pcm_t *pcm, int err) return err; }
+/** + * \retval number of frames available to the application for playback + * + * This is how far ahead the hardware position in the ring buffer is, + * compared to the application position. ie. for playback it's the + * number of frames in the empty part of the ring buffer. + */ static inline snd_pcm_uframes_t __snd_pcm_playback_avail(snd_pcm_t *pcm, const snd_pcm_uframes_t hw_ptr, const snd_pcm_uframes_t appl_ptr) @@ -498,6 +505,13 @@ static inline snd_pcm_uframes_t snd_pcm_mmap_playback_avail(snd_pcm_t *pcm) return __snd_pcm_playback_avail(pcm, *pcm->hw.ptr, *pcm->appl.ptr); }
+/* + * \retval number of frames available to the application for capture + * + * This is how far ahead the hardware position in the ring buffer is + * compared to the application position. ie. for capture, it's the + * number of frames in the filled part of the ring buffer. + */ static inline snd_pcm_uframes_t __snd_pcm_capture_avail(snd_pcm_t *pcm, const snd_pcm_uframes_t hw_ptr, const snd_pcm_uframes_t appl_ptr) @@ -529,11 +543,21 @@ static inline snd_pcm_uframes_t snd_pcm_mmap_avail(snd_pcm_t *pcm) return __snd_pcm_avail(pcm, *pcm->hw.ptr, *pcm->appl.ptr); }
+/* + * \retval number of frames available to the hardware for playback + * + * ie. the filled part of the ring buffer + */ static inline snd_pcm_sframes_t snd_pcm_mmap_playback_hw_avail(snd_pcm_t *pcm) { return pcm->buffer_size - snd_pcm_mmap_playback_avail(pcm); }
+/* + * \retval number of frames available to the hardware for capture + * + * ie. the empty part of the ring buffer. + */ static inline snd_pcm_sframes_t snd_pcm_mmap_capture_hw_avail(snd_pcm_t *pcm) { return pcm->buffer_size - snd_pcm_mmap_capture_avail(pcm);