sys/chunked_ringbuffer: discard stale chunk when starting a new one

sys/include/chunked_ringbuffer.h

@@ -72,9 +72,26 @@ typedef void (*crb_foreach_callback_t)(void *ctx, uint8_t *bytes, size_t len);
  */
 void crb_init(chunk_ringbuf_t *rb, void *buffer, size_t len);
 
+/**
+ * @brief Close the current chunk
+ *
+ * @note  This function is expected to be called in ISR context / with
+ *        interrupts disabled.
+ *
+ * @param[in] rb        The Ringbuffer to work on
+ * @param[in] valid     True if the chunk is valid and should be stored
+ *                      False if the current chunk should be discarded
+ *
+ * @return true         If the chunk could be stored in the valid chunk array
+ * @return false        If there is no more space in the valid chunk array
+ */
+bool crb_end_chunk(chunk_ringbuf_t *rb, bool valid);
+
 /**
  * @brief Start a new chunk on the ringbuffer
  *
+ * If an unfinished chunk already exists, it will be discarded.
+ *
  * @note  This function is expected to be called in ISR context / with
  *        interrupts disabled.
  *
@@ -85,6 +102,11 @@ void crb_init(chunk_ringbuf_t *rb, void *buffer, size_t len);
  */
 static inline bool crb_start_chunk(chunk_ringbuf_t *rb)
 {
+    /* discard stale chunk */
+    if (rb->cur_start) {
+        crb_end_chunk(rb, false);
+    }
+
     /* pointing to the start of the first chunk */
     if (rb->cur == rb->protect) {
         return false;
@@ -150,21 +172,6 @@ static inline bool crb_add_byte(chunk_ringbuf_t *rb, uint8_t b)
  */
 bool crb_add_bytes(chunk_ringbuf_t *rb, const void *data, size_t len);
 
-/**
- * @brief Close the current chunk
- *
- * @note  This function is expected to be called in ISR context / with
- *        interrupts disabled.
- *
- * @param[in] rb        The Ringbuffer to work on
- * @param[in] valid     True if the chunk is valid and should be stored
- *                      False if the current chunk should be discarded
- *
- * @return true         If the chunk could be stored in the valid chunk array
- * @return false        If there is no more space in the valid chunk array
- */
-bool crb_end_chunk(chunk_ringbuf_t *rb, bool valid);
-
 /**
  * @brief Add a complete chunk to the Ringbuffer
  *