--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/twjit_out.c	Fri Jul 05 21:24:56 2024 +0000
@@ -0,0 +1,117 @@
+/*
+ * Themyscira Wireless jitter buffer implementation:
+ * output to the fixed timing system.
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/utils.h>
+
+#include <themwi/rtp/twjit.h>
+
+static bool starting_sb_is_ready(struct twrtp_jibuf_inst *twjit)
+{
+	struct twrtp_jibuf_sub *sb = &twjit->sb[twjit->write_sb];
+
+	if (sb->depth < sb->conf.bd_start)
+		return false;
+	if (sb->delta_ms < sb->conf.start_min_delta)
+		return false;
+	return true;
+}
+
+static bool read_sb_is_empty(struct twrtp_jibuf_inst *twjit)
+{
+	struct twrtp_jibuf_sub *sb = &twjit->sb[twjit->read_sb];
+
+	return sb->depth == 0;
+}
+
+static struct msgb *pull_from_read_sb(struct twrtp_jibuf_inst *twjit)
+{
+	struct twrtp_jibuf_sub *sb = &twjit->sb[twjit->read_sb];
+	struct msgb *msg;
+
+	OSMO_ASSERT(!llist_empty(&sb->queue));
+	OSMO_ASSERT(sb->depth > 0);
+	msg = llist_entry(sb->queue.next, struct msgb, list);
+	if (msg->cb[0] == sb->head_ts) {
+		llist_del(&msg->list);
+		twjit->stats.delivered_pkt++;
+		twjit->stats.delivered_bytes += msg->len;
+	} else {
+		msg = NULL;
+		twjit->stats.output_gaps++;
+	}
+	sb->head_ts += twjit->ts_quantum;
+	sb->depth--;
+	return msg;
+}
+
+static void read_sb_thinning(struct twrtp_jibuf_inst *twjit)
+{
+	struct twrtp_jibuf_sub *sb = &twjit->sb[twjit->read_sb];
+	struct msgb *msg;
+
+	if (sb->drop_int_count) {
+		sb->drop_int_count--;
+		return;
+	}
+	if (sb->depth <= sb->conf.bd_hiwat)
+		return;
+	twjit->stats.thinning_drops++;
+	msg = pull_from_read_sb(twjit);
+	if (msg)
+		msgb_free(msg);
+	sb->drop_int_count = sb->conf.thinning_int - 2;
+}
+
+static void toss_read_queue(struct twrtp_jibuf_inst *twjit)
+{
+	struct twrtp_jibuf_sub *sb = &twjit->sb[twjit->read_sb];
+
+	msgb_queue_free(&sb->queue);
+	sb->depth = 0;
+}
+
+struct msgb *twrtp_jibuf_output(struct twrtp_jibuf_inst *twjit)
+{
+	switch (twjit->state) {
+	case TWJIT_STATE_EMPTY:
+		return NULL;
+	case TWJIT_STATE_HUNT:
+		if (!starting_sb_is_ready(twjit))
+			return NULL;
+		twjit->state = TWJIT_STATE_FLOWING;
+		twjit->read_sb = twjit->write_sb;
+		return pull_from_read_sb(twjit);
+	case TWJIT_STATE_FLOWING:
+		if (read_sb_is_empty(twjit)) {
+			twjit->state = TWJIT_STATE_EMPTY;
+			twjit->stats.underruns++;
+			return NULL;
+		}
+		read_sb_thinning(twjit);
+		return pull_from_read_sb(twjit);
+	case TWJIT_STATE_HANDOVER:
+		if (starting_sb_is_ready(twjit)) {
+			toss_read_queue(twjit);
+			twjit->state = TWJIT_STATE_FLOWING;
+			twjit->read_sb = twjit->write_sb;
+			return pull_from_read_sb(twjit);
+		}
+		if (read_sb_is_empty(twjit)) {
+			twjit->state = TWJIT_STATE_HUNT;
+			twjit->stats.underruns++;
+			return NULL;
+		}
+		read_sb_thinning(twjit);
+		return pull_from_read_sb(twjit);
+	default:
+		OSMO_ASSERT(0);
+	}
+}