harden USB telemetry transport

main/trikke_transport.h

@@ -0,0 +1,48 @@
+#pragma once
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef enum {
+    TRIKKE_TRANSPORT_COMPLETE = 0,
+    TRIKKE_TRANSPORT_RETRY,
+    TRIKKE_TRANSPORT_PENDING,
+    TRIKKE_TRANSPORT_FATAL,
+} trikke_transport_status_t;
+
+typedef trikke_transport_status_t (*trikke_transport_begin_fn)(
+    void *context,
+    const uint8_t *packet,
+    size_t packet_size);
+
+typedef trikke_transport_status_t (*trikke_transport_poll_fn)(void *context);
+
+typedef struct {
+    void *context;
+    trikke_transport_begin_fn begin;
+    trikke_transport_poll_fn poll;
+} trikke_transport_t;
+
+typedef struct {
+    bool pending;
+} trikke_transport_sender_t;
+
+void trikke_transport_sender_init(trikke_transport_sender_t *sender);
+
+// Advances one bounded transport operation. The packet storage must remain valid
+// and unchanged from the first PENDING result through COMPLETE. While pending,
+// only poll is called: an ambiguous timeout can never duplicate a frame.
+trikke_transport_status_t trikke_transport_sender_step(
+    trikke_transport_sender_t *sender,
+    const trikke_transport_t *transport,
+    const uint8_t *packet,
+    size_t packet_size);
+
+#ifdef __cplusplus
+}
+#endif