changeset 494:aaf4dec8bee0

libgsmhr1: implement perfect SID detection
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 17 Jun 2024 23:14:19 +0000
parents dc7249923b3a
children aee13079db3c
files libgsmhr1/Makefile libgsmhr1/sid_detect.c
diffstat 2 files changed, 24 insertions(+), 1 deletions(-) [+]
line wrap: on
line diff
--- a/libgsmhr1/Makefile	Mon Jun 17 23:00:57 2024 +0000
+++ b/libgsmhr1/Makefile	Mon Jun 17 23:14:19 2024 +0000
@@ -1,4 +1,5 @@
-OBJS=	pack_frame.o rtp_in.o twts002_in.o twts002_out.o unpack_frame.o
+OBJS=	pack_frame.o rtp_in.o sid_detect.o twts002_in.o twts002_out.o \
+	unpack_frame.o
 HDRS=	tw_gsmhr.h
 LIB=	libgsmhr1.a
 
--- /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;
+}