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rawmidi: define more abstract API for the timestamp reads

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The frame structure is a bit internal thing for the kernel
data transfer implementation. Introduce snd_rawmidi_tread()
function which is straight for the application usage and hides
the framing data transfers (kernel space API).

The current code implements the read cache and does the merging
of the frame reads with the similar timestamps (opposite
to the kernel data split for big chunks).

If the application wants to use super-duper-lighting-fast reads,
the snd_rawmidi_read() may be used, but the structure must be
defined on it's own, because this mechanism is not preferred
and unsupported.

BugLink: https://github.com/alsa-project/alsa-lib/issues/172
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
This commit is contained in:
Jaroslav Kysela 2021-08-24 11:36:30 +02:00
parent 42eeb5eca0
commit 5a5c2953ea
5 changed files with 144 additions and 37 deletions
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21
include/rawmidi.h
View file

@ -93,26 +93,6 @@ typedef enum _snd_rawmidi_framing {
SND_RAWMIDI_FRAMING_TSTAMP = 1,
} snd_rawmidi_framing_t;
#define SND_RAWMIDI_FRAME_TYPE_DEFAULT 0
#define SND_RAWMIDI_FRAMING_DATA_LENGTH 16
/** Incoming RawMidi bytes is put inside this container if tstamp type framing is enabled. */
struct _snd_rawmidi_framing_tstamp {
/**
* For now, frame_type is always SND_RAWMIDI_FRAME_TYPE_DEFAULT.
* Midi 2.0 is expected to add new types here.
* Applications are expected to skip unknown frame types.
*/
uint8_t frame_type;
uint8_t length; /* number of valid bytes in data field */
uint8_t reserved[2];
uint32_t tv_nsec; /* nanoseconds */
uint64_t tv_sec; /* seconds */
uint8_t data[SND_RAWMIDI_FRAMING_DATA_LENGTH];
} __attribute__((packed));
typedef struct _snd_rawmidi_framing_tstamp snd_rawmidi_framing_tstamp_t;
int snd_rawmidi_open(snd_rawmidi_t **in_rmidi, snd_rawmidi_t **out_rmidi,
const char *name, int mode);
int snd_rawmidi_open_lconf(snd_rawmidi_t **in_rmidi, snd_rawmidi_t **out_rmidi,
@ -184,6 +164,7 @@ int snd_rawmidi_drain(snd_rawmidi_t *rmidi);
int snd_rawmidi_drop(snd_rawmidi_t *rmidi);
ssize_t snd_rawmidi_write(snd_rawmidi_t *rmidi, const void *buffer, size_t size);
ssize_t snd_rawmidi_read(snd_rawmidi_t *rmidi, void *buffer, size_t size);
ssize_t snd_rawmidi_tread(snd_rawmidi_t *rmidi, struct timespec *tstamp, void *buffer, size_t size);
const char *snd_rawmidi_name(snd_rawmidi_t *rmidi);
snd_rawmidi_type_t snd_rawmidi_type(snd_rawmidi_t *rmidi);
snd_rawmidi_stream_t snd_rawmidi_stream(snd_rawmidi_t *rawmidi);