libosmocoding: migrate transcoding routines from OsmoBTS

There are some projects, such as GR-GSM and OsmocomBB, which would
benefit from using one shared implementation of GSM 05.03 code. So,
this commit introduces a new sub-library called libosmocoding, which
(for now) provides GSM, GPRS and EDGE transcoding routines, migrated
from OsmoBTS.

The original GSM 05.03 code from OsmoBTS was relicensed under
GPLv2-or-later with permission of copyright holders (Andreas Eversberg,
Alexander Chemeris and Tom Tsou).

The following data types are currently supported:

 - xCCH
 - PDTCH (CS 1-4 and MCS 1-9)
 - TCH/FR
 - TCH/HR
 - TCH/AFS
 - RCH/AHS
 - RACH
 - SCH

Change-Id: I0c3256b87686d878e4e716d12393cad5924fdfa1

1 files changed, 132 insertions, 0 deletions

diff --git a/src/coding/gsm0503_parity.c b/src/coding/gsm0503_parity.c
new file mode 100644
index 00000000..99198ba8
--- /dev/null
+++ b/src/coding/gsm0503_parity.c
@@ -0,0 +1,132 @@
+/*
+ * (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
+ * (C) 2016 by Tom Tsou <tom.tsou@ettus.com>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include <stdint.h>
+
+#include <osmocom/core/crcgen.h>
+#include <osmocom/coding/gsm0503_parity.h>
+
+/*
+ * GSM (SACCH) parity (FIRE code)
+ *
+ * g(x) = (x^23 + 1)(x^17 + x^3 + 1)
+ *      = x^40 + x^26 + x^23 + x^17 + x^3 + a1
+ */
+const struct osmo_crc64gen_code gsm0503_fire_crc40 = {
+	.bits = 40,
+	.poly = 0x0004820009ULL,
+	.init = 0x0000000000ULL,
+	.remainder = 0xffffffffffULL,
+};
+
+/*
+ * GSM PDTCH CS-2, CS-3, CS-4 parity
+ *
+ * g(x) = x^16 + x^12 + x^5 + 1
+ */
+const struct osmo_crc16gen_code gsm0503_cs234_crc16 = {
+	.bits = 16,
+	.poly = 0x1021,
+	.init = 0x0000,
+	.remainder = 0xffff,
+};
+
+/*
+ * EDGE MCS header parity
+ *
+ */
+const struct osmo_crc8gen_code gsm0503_mcs_crc8_hdr = {
+	.bits = 8,
+	.poly = 0x49,
+	.init = 0x00,
+	.remainder = 0xff,
+};
+
+/*
+ * EDGE MCS data parity
+ *
+ */
+const struct osmo_crc16gen_code gsm0503_mcs_crc12 = {
+	.bits = 12,
+	.poly = 0x0d31,
+	.init = 0x0000,
+	.remainder = 0x0fff,
+};
+
+/*
+ * GSM RACH parity
+ *
+ * g(x) = x^6 + x^5 + x^3 + x^2 + x^1 + 1
+ */
+const struct osmo_crc8gen_code gsm0503_rach_crc6 = {
+	.bits = 6,
+	.poly = 0x2f,
+	.init = 0x00,
+	.remainder = 0x3f,
+};
+
+/*
+ * GSM SCH parity
+ *
+ * g(x) = x^10 + x^8 + x^6 + x^5 + x^4 + x^2 + 1
+ */
+const struct osmo_crc16gen_code gsm0503_sch_crc10 = {
+	.bits = 10,
+	.poly = 0x175,
+	.init = 0x000,
+	.remainder = 0x3ff,
+};
+
+/*
+ * GSM TCH FR/HR/EFR parity
+ *
+ * g(x) = x^3 + x + 1
+ */
+const struct osmo_crc8gen_code gsm0503_tch_fr_crc3 = {
+	.bits = 3,
+	.poly = 0x3,
+	.init = 0x0,
+	.remainder = 0x7,
+};
+
+/*
+ * GSM TCH EFR parity
+ *
+ * g(x) = x^8 + x^4 + x^3 + x^2 + 1
+ */
+const struct osmo_crc8gen_code gsm0503_tch_efr_crc8 = {
+	.bits = 8,
+	.poly = 0x1d,
+	.init = 0x00,
+	.remainder = 0x00,
+};
+
+/*
+ * GSM AMR parity
+ *
+ * g(x) = x^6 + x^5 + x^3 + x^2 + x^1 + 1
+ */
+const struct osmo_crc8gen_code gsm0503_amr_crc6 = {
+	.bits = 6,
+	.poly = 0x2f,
+	.init = 0x00,
+	.remainder = 0x3f,
+};