# HG changeset patch
# User Mychaela Falconia <falcon@freecalypso.org>
# Date 1719221308 0
# Node ID bacc590ec839f864298e02ed63a6937dbedc0acc
# Parent  2ee910aa03c3b6dce6407f9ee1254ab7ebd92949
ater: implement EFR CRC inversion option

diff -r 2ee910aa03c3 -r bacc590ec839 ater/out_frame.c
--- a/ater/out_frame.c	Mon Jun 24 09:20:54 2024 +0000
+++ b/ater/out_frame.c	Mon Jun 24 09:28:28 2024 +0000
@@ -99,10 +99,18 @@
 	}
 }
 
+static void invert_crc3(ubit_t *crc)
+{
+	crc[0] = !crc[0];
+	crc[1] = !crc[1];
+	crc[2] = !crc[2];
+}
+
 static void fill_data_efr(const uint8_t *data, struct osmo_trau_frame *tf)
 {
 	int i, j;
 	ubit_t check_bits[26];
+	uint8_t crc_inv;
 
 	/* reassemble d-bits */
 	tf->d_bits[0] = 1;
@@ -131,6 +139,19 @@
 	efr_parity_bits_5(check_bits, tf->d_bits);
 	osmo_crc8gen_set_bits(&gsm0860_efr_crc3, check_bits, 8,
 			tf->d_bits + 257);
+
+	/* inverted CRC option */
+	crc_inv = data[31];
+	if (crc_inv & 0x80)
+		invert_crc3(tf->d_bits + 39);
+	if (crc_inv & 0x40)
+		invert_crc3(tf->d_bits + 95);
+	if (crc_inv & 0x20)
+		invert_crc3(tf->d_bits + 148);
+	if (crc_inv & 0x10)
+		invert_crc3(tf->d_bits + 204);
+	if (crc_inv & 0x08)
+		invert_crc3(tf->d_bits + 257);
 }
 
 void trau_frame_from_record(const uint8_t *rec, bool is_efr,