til: add preliminary audio backend

This is an early implementation of something resembling an audio
backend for rototiller/libtil.

The assumption for now is that everything will use signed 16-bit
native-endian stereo output @ 44.1khz.

1 files changed, 148 insertions, 0 deletions

diff --git a/src/til_audio.c b/src/til_audio.c
new file mode 100644
index 0000000..ed1ff9b
--- /dev/null
+++ b/src/til_audio.c
@@ -0,0 +1,148 @@
+#include <assert.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "til_audio.h"
+#include "til_audio_context.h"
+
+
+/* initialize audio via ops using setup, context stored in res_audio_context on success.
+ * returns -errno on error, 0 on success
+ * playback is left in a paused state, with an empty queue
+ */
+int til_audio_open(const til_audio_ops_t *ops, til_setup_t *setup, til_audio_context_t **res_audio_context)
+{
+	til_audio_context_t	*c;
+	int			r;
+
+	assert(ops);
+	assert(ops->init);
+	assert(ops->queue);
+	assert(ops->n_queued);
+	assert(setup);
+	assert(res_audio_context);
+
+	r = ops->init(setup, &c);
+	if (r < 0)
+		return r;
+
+	*res_audio_context = c;
+
+	return 0;
+}
+
+
+/* closes audio and frees context,
+ * callers are expected to use this and not til_audio_context_free().
+ */
+void til_audio_shutdown(til_audio_context_t *audio_context)
+{
+	assert(audio_context);
+	assert(audio_context->ops);
+
+	if (audio_context->ops->shutdown)
+		audio_context->ops->shutdown(audio_context);
+
+	til_audio_context_free(audio_context);
+}
+
+
+/* install audio hooks to receive notification on events like seek/pause/unpause */
+int til_audio_set_hooks(til_audio_context_t *audio_context, til_audio_hooks_t *hooks, void *hooks_context)
+{
+	assert(audio_context);
+	assert(hooks);
+
+	if (audio_context->hooks && audio_context->hooks != hooks)
+		return -EEXIST;
+
+	audio_context->hooks = hooks;
+	audio_context->hooks_context = hooks_context;
+
+	return 0;
+}
+
+
+/* remove audio hooks */
+int til_audio_unset_hooks(til_audio_context_t *audio_context, til_audio_hooks_t *hooks, void *hooks_context)
+{
+	assert(audio_context);
+	assert(hooks);
+
+	/* this is kind of silly, but seems potentially useful in the defensive department */
+	if (audio_context->hooks != hooks ||
+	    audio_context->hooks_context != hooks_context)
+		return -EINVAL;
+
+	audio_context->hooks = NULL;
+	audio_context->hooks_context = NULL;
+
+	return 0;
+}
+
+
+/* seek to an absolute ticks, playback is left in a paused state with an empty queue */
+void til_audio_seek(til_audio_context_t *audio_context, unsigned ticks)
+{
+	assert(audio_context);
+
+	if (audio_context->ops->pause)
+		audio_context->ops->pause(audio_context);
+
+	if (audio_context->ops->drop)
+		audio_context->ops->drop(audio_context);
+
+	if (audio_context->hooks && audio_context->hooks->seeked)
+		audio_context->hooks->seeked(audio_context->hooks_context, audio_context, ticks);
+}
+
+
+/* queue n_frames frames to audio_context,
+ * returns 0 on success, -errno on error
+ */
+int til_audio_queue(til_audio_context_t *audio_context, int16_t *frames, int n_frames)
+{
+	assert(audio_context);
+	assert(frames);
+	assert(n_frames > 0);
+
+	return audio_context->ops->queue(audio_context, frames, n_frames);
+}
+
+
+/* query how many frames are currently queued
+ * returns 0 on success, -errno on error
+ */
+unsigned til_audio_n_queued(til_audio_context_t *audio_context)
+{
+	assert(audio_context);
+
+	return audio_context->ops->n_queued(audio_context);
+}
+
+
+/* pause the underlying audio playback, queue is left as-is, should be idempotent */
+void til_audio_pause(til_audio_context_t *audio_context)
+{
+	assert(audio_context);
+
+	if (audio_context->ops->pause)
+		audio_context->ops->pause(audio_context);
+
+	if (audio_context->hooks && audio_context->hooks->paused)
+		audio_context->hooks->paused(audio_context->hooks_context, audio_context);
+}
+
+
+/* unpause the underlying audio playback, queue is left as-is, should be idempotent */
+void til_audio_unpause(til_audio_context_t *audio_context)
+{
+	assert(audio_context);
+
+	if (audio_context->ops->unpause)
+		audio_context->ops->unpause(audio_context);
+
+	if (audio_context->hooks && audio_context->hooks->unpaused)
+		audio_context->hooks->unpaused(audio_context->hooks_context, audio_context);
+}