--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libgsmhr1/sid_detect.c	Mon Jun 17 23:14:19 2024 +0000
@@ -0,0 +1,22 @@
+/*
+ * The function in this module implements detection of perfect, error-free
+ * HRv1 SID frames in TS 101 318 raw packed format.  If SID is detected,
+ * the return value is 2: the code for valid SID per GSM 06.41.
+ */
+
+#include <stdint.h>
+#include <string.h>
+#include "tw_gsmhr.h"
+
+int gsmhr_ts101318_is_perfect_sid(const uint8_t *payload)
+{
+	static const uint8_t all_ff_bytes[9] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
+						0xFF, 0xFF, 0xFF, 0xFF};
+
+	if ((payload[4] & 0x7F) != 0x7F)
+		return 0;
+	if (memcmp(payload + 5, all_ff_bytes, 9) == 0)
+		return 2;
+	else
+		return 0;
+}