+/**
+ * Gets the Rolling Proximity Identifier for the device in binary format.
+ *
+ * For internal use. It generally makes more sense to use the
+ * contrac_get_proximity_id() function instead.
+ *
+ * This allows the Rolling Proximity Identifier to be extracted. The Rolling
+ * Proximity Identifier is public, in the sense that it is usual to broadcast
+ * the value in Bluetooth beacons.
+ *
+ * The buffer returned will contain exactly RPI_SIZE (16) bytes of data in
+ * binary format. This may therefore contain null bytes, and the buffer will not
+ * necessarily be null terminated. Future operations may cause the data to
+ * change, so the caller should make a copy of the buffer rather than keeping
+ * a pointer to it.
+ *
+ * @param data The context object to work with.
+ * @return The Rolling Proximity Identifier in binary format, not null
+ * terminated.
+ */
+unsigned char const * rpi_get_proximity_id(Rpi const * data) {