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

7 files changed, 5553 insertions, 0 deletions

diff --git a/src/coding/Makefile.am b/src/coding/Makefile.am
new file mode 100644
index 00000000..5a055c8d
--- /dev/null
+++ b/src/coding/Makefile.am
@@ -0,0 +1,27 @@
+# This is _NOT_ the library release version, it's an API version.
+# Please read Chapter 6 "Library interface versions" of the libtool
+# documentation before making any modification
+LIBVERSION = 0:0:0
+
+AM_CPPFLAGS = -I$(top_srcdir)/include $(TALLOC_CFLAGS)
+AM_CFLAGS = -Wall
+
+lib_LTLIBRARIES = libosmocoding.la
+
+libosmocoding_la_SOURCES = \
+	gsm0503_interleaving.c \
+	gsm0503_mapping.c \
+	gsm0503_tables.c \
+	gsm0503_parity.c \
+	gsm0503_coding.c
+libosmocoding_la_LDFLAGS = \
+	-version-info \
+	$(LIBVERSION) \
+	-no-undefined \
+	$(TALLOC_LIBS)
+libosmocoding_la_LIBADD = \
+	../libosmocore.la \
+	../gsm/libosmogsm.la \
+	../codec/libosmocodec.la
+
+EXTRA_DIST = libosmocoding.map
diff --git a/src/coding/gsm0503_coding.c b/src/coding/gsm0503_coding.c
new file mode 100644
index 00000000..30ec387b
--- /dev/null
+++ b/src/coding/gsm0503_coding.c
@@ -0,0 +1,2681 @@
+/*
+ * (C) 2013 by Andreas Eversberg <jolly@eversberg.eu>
+ * (C) 2015 by Alexander Chemeris <Alexander.Chemeris@fairwaves.co>
+ * (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 <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+
+#include <osmocom/core/bits.h>
+#include <osmocom/core/conv.h>
+#include <osmocom/core/utils.h>
+#include <osmocom/core/crcgen.h>
+#include <osmocom/core/endian.h>
+
+#include <osmocom/gprs/protocol/gsm_04_60.h>
+#include <osmocom/gprs/gprs_rlc.h>
+
+#include <osmocom/gsm/protocol/gsm_04_08.h>
+#include <osmocom/gsm/gsm0503.h>
+#include <osmocom/codec/codec.h>
+
+#include <osmocom/coding/gsm0503_interleaving.h>
+#include <osmocom/coding/gsm0503_mapping.h>
+#include <osmocom/coding/gsm0503_tables.h>
+#include <osmocom/coding/gsm0503_coding.h>
+#include <osmocom/coding/gsm0503_parity.h>
+
+/*
+ * EGPRS coding limits
+ */
+
+/* Max header size with parity bits */
+#define EGPRS_HDR_UPP_MAX	54
+
+/* Max encoded header size */
+#define EGPRS_HDR_C_MAX		162
+
+/* Max punctured header size */
+#define EGPRS_HDR_HC_MAX	160
+
+/* Max data block size with parity bits */
+#define EGPRS_DATA_U_MAX	612
+
+/* Max encoded data block size */
+#define EGPRS_DATA_C_MAX	1836
+
+/* Max single block punctured data size */
+#define EGPRS_DATA_DC_MAX	1248
+
+/* Dual block punctured data size */
+#define EGPRS_DATA_C1		612
+#define EGPRS_DATA_C2		EGPRS_DATA_C1
+
+/* TS 101318 Chapter 5.1: 260 bits + 4bit sig */
+#define GSM_FR_BYTES	33
+/* TS 101318 Chapter 5.2: 112 bits, no sig */
+#define GSM_HR_BYTES	14
+/* TS 101318 Chapter 5.3: 244 bits + 4bit sig */
+#define GSM_EFR_BYTES	31
+
+union gprs_rlc_ul_hdr_egprs {
+	struct gprs_rlc_ul_header_egprs_1 type1;
+	struct gprs_rlc_ul_header_egprs_2 type2;
+	struct gprs_rlc_ul_header_egprs_3 type3;
+};
+
+union gprs_rlc_dl_hdr_egprs {
+	struct gprs_rlc_dl_header_egprs_1 type1;
+	struct gprs_rlc_dl_header_egprs_2 type2;
+	struct gprs_rlc_dl_header_egprs_3 type3;
+};
+
+struct gsm0503_mcs_code {
+	uint8_t mcs;
+	uint8_t usf_len;
+
+	/* Header coding */
+	uint8_t hdr_len;
+	uint8_t hdr_code_len;
+	uint8_t hdr_punc_len;
+	const struct osmo_conv_code *hdr_conv;
+	const uint8_t *hdr_punc;
+
+	/* Data coding */
+	uint16_t data_len;
+	uint16_t data_code_len;
+	uint16_t data_punc_len;
+	const struct osmo_conv_code *data_conv;
+	const uint8_t *data_punc[3];
+};
+
+/*
+ * EGPRS UL coding parameters
+ */
+struct gsm0503_mcs_code gsm0503_mcs_ul_codes[EGPRS_NUM_MCS] = {
+	{
+		.mcs = EGPRS_MCS0,
+	},
+	{
+		.mcs = EGPRS_MCS1,
+		.hdr_len = 31,
+		.hdr_code_len = 117,
+		.hdr_punc_len = 80,
+		.hdr_conv = &gsm0503_mcs1_ul_hdr,
+		.hdr_punc = gsm0503_puncture_mcs1_ul_hdr,
+
+		.data_len = 178,
+		.data_code_len = 588,
+		.data_punc_len = 372,
+		.data_conv = &gsm0503_mcs1,
+		.data_punc = {
+			gsm0503_puncture_mcs1_p1,
+			gsm0503_puncture_mcs1_p2,
+			NULL,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS2,
+		.hdr_len = 31,
+		.hdr_code_len = 117,
+		.hdr_punc_len = 80,
+		.hdr_conv = &gsm0503_mcs1_ul_hdr,
+		.hdr_punc = gsm0503_puncture_mcs1_ul_hdr,
+
+		.data_len = 226,
+		.data_code_len = 732,
+		.data_punc_len = 372,
+		.data_conv = &gsm0503_mcs2,
+		.data_punc = {
+			gsm0503_puncture_mcs2_p1,
+			gsm0503_puncture_mcs2_p2,
+			NULL,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS3,
+		.hdr_len = 31,
+		.hdr_code_len = 117,
+		.hdr_punc_len = 80,
+		.hdr_conv = &gsm0503_mcs1_ul_hdr,
+		.hdr_punc = gsm0503_puncture_mcs1_ul_hdr,
+
+		.data_len = 298,
+		.data_code_len = 948,
+		.data_punc_len = 372,
+		.data_conv = &gsm0503_mcs3,
+		.data_punc = {
+			gsm0503_puncture_mcs3_p1,
+			gsm0503_puncture_mcs3_p2,
+			gsm0503_puncture_mcs3_p3,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS4,
+		.hdr_len = 31,
+		.hdr_code_len = 117,
+		.hdr_punc_len = 80,
+		.hdr_conv = &gsm0503_mcs1_ul_hdr,
+		.hdr_punc = gsm0503_puncture_mcs1_ul_hdr,
+
+		.data_len = 354,
+		.data_code_len = 1116,
+		.data_punc_len = 372,
+		.data_conv = &gsm0503_mcs4,
+		.data_punc = {
+			gsm0503_puncture_mcs4_p1,
+			gsm0503_puncture_mcs4_p2,
+			gsm0503_puncture_mcs4_p3,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS5,
+		.hdr_len = 37,
+		.hdr_code_len = 135,
+		.hdr_punc_len = 136,
+		.hdr_conv = &gsm0503_mcs5_ul_hdr,
+		.hdr_punc = NULL,
+
+		.data_len = 450,
+		.data_code_len = 1404,
+		.data_punc_len = 1248,
+		.data_conv = &gsm0503_mcs5,
+		.data_punc = {
+			gsm0503_puncture_mcs5_p1,
+			gsm0503_puncture_mcs5_p2,
+			NULL,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS6,
+		.hdr_len = 37,
+		.hdr_code_len = 135,
+		.hdr_punc_len = 136,
+		.hdr_conv = &gsm0503_mcs5_ul_hdr,
+		.hdr_punc = NULL,
+
+		.data_len = 594,
+		.data_code_len = 1836,
+		.data_punc_len = 1248,
+		.data_conv = &gsm0503_mcs6,
+		.data_punc = {
+			gsm0503_puncture_mcs6_p1,
+			gsm0503_puncture_mcs6_p2,
+			NULL,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS7,
+		.hdr_len = 46,
+		.hdr_code_len = 162,
+		.hdr_punc_len = 160,
+		.hdr_conv = &gsm0503_mcs7_ul_hdr,
+		.hdr_punc = gsm0503_puncture_mcs7_ul_hdr,
+
+		.data_len = 900,
+		.data_code_len = 1404,
+		.data_punc_len = 612,
+		.data_conv = &gsm0503_mcs7,
+		.data_punc = {
+			gsm0503_puncture_mcs7_p1,
+			gsm0503_puncture_mcs7_p2,
+			gsm0503_puncture_mcs7_p3,
+		}
+	},
+	{
+		.mcs = EGPRS_MCS8,
+		.hdr_len = 46,
+		.hdr_code_len = 162,
+		.hdr_punc_len = 160,
+		.hdr_conv = &gsm0503_mcs7_ul_hdr,
+		.hdr_punc = gsm0503_puncture_mcs7_ul_hdr,
+
+		.data_len = 1092,
+		.data_code_len = 1692,
+		.data_punc_len = 612,
+		.data_conv = &gsm0503_mcs8,
+		.data_punc = {
+			gsm0503_puncture_mcs8_p1,
+			gsm0503_puncture_mcs8_p2,
+			gsm0503_puncture_mcs8_p3,
+		}
+	},
+	{
+		.mcs = EGPRS_MCS9,
+		.hdr_len = 46,
+		.hdr_code_len = 162,
+		.hdr_punc_len = 160,
+		.hdr_conv = &gsm0503_mcs7_ul_hdr,
+		.hdr_punc = gsm0503_puncture_mcs7_ul_hdr,
+
+		.data_len = 1188,
+		.data_code_len = 1836,
+		.data_punc_len = 612,
+		.data_conv = &gsm0503_mcs9,
+		.data_punc = {
+			gsm0503_puncture_mcs9_p1,
+			gsm0503_puncture_mcs9_p2,
+			gsm0503_puncture_mcs9_p3,
+		}
+	},
+};
+
+/*
+ * EGPRS DL coding parameters
+ */
+struct gsm0503_mcs_code gsm0503_mcs_dl_codes[EGPRS_NUM_MCS] = {
+	{
+		.mcs = EGPRS_MCS0,
+	},
+	{
+		.mcs = EGPRS_MCS1,
+		.usf_len = 3,
+		.hdr_len = 28,
+		.hdr_code_len = 108,
+		.hdr_punc_len = 68,
+		.hdr_conv = &gsm0503_mcs1_dl_hdr,
+		.hdr_punc = gsm0503_puncture_mcs1_dl_hdr,
+
+		.data_len = 178,
+		.data_code_len = 588,
+		.data_punc_len = 372,
+		.data_conv = &gsm0503_mcs1,
+		.data_punc = {
+			gsm0503_puncture_mcs1_p1,
+			gsm0503_puncture_mcs1_p2,
+			NULL,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS2,
+		.usf_len = 3,
+		.hdr_len = 28,
+		.hdr_code_len = 108,
+		.hdr_punc_len = 68,
+		.hdr_conv = &gsm0503_mcs1_dl_hdr,
+		.hdr_punc = gsm0503_puncture_mcs1_dl_hdr,
+
+		.data_len = 226,
+		.data_code_len = 732,
+		.data_punc_len = 372,
+		.data_conv = &gsm0503_mcs2,
+		.data_punc = {
+			gsm0503_puncture_mcs2_p1,
+			gsm0503_puncture_mcs2_p2,
+			NULL,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS3,
+		.usf_len = 3,
+		.hdr_len = 28,
+		.hdr_code_len = 108,
+		.hdr_punc_len = 68,
+		.hdr_conv = &gsm0503_mcs1_dl_hdr,
+		.hdr_punc = gsm0503_puncture_mcs1_dl_hdr,
+
+		.data_len = 298,
+		.data_code_len = 948,
+		.data_punc_len = 372,
+		.data_conv = &gsm0503_mcs3,
+		.data_punc = {
+			gsm0503_puncture_mcs3_p1,
+			gsm0503_puncture_mcs3_p2,
+			gsm0503_puncture_mcs3_p3,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS4,
+		.usf_len = 3,
+		.hdr_len = 28,
+		.hdr_code_len = 108,
+		.hdr_punc_len = 68,
+		.hdr_conv = &gsm0503_mcs1_dl_hdr,
+		.hdr_punc = gsm0503_puncture_mcs1_dl_hdr,
+
+		.data_len = 354,
+		.data_code_len = 1116,
+		.data_punc_len = 372,
+		.data_conv = &gsm0503_mcs4,
+		.data_punc = {
+			gsm0503_puncture_mcs4_p1,
+			gsm0503_puncture_mcs4_p2,
+			gsm0503_puncture_mcs4_p3,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS5,
+		.usf_len = 3,
+		.hdr_len = 25,
+		.hdr_code_len = 99,
+		.hdr_punc_len = 100,
+		.hdr_conv = &gsm0503_mcs5_dl_hdr,
+		.hdr_punc = NULL,
+
+		.data_len = 450,
+		.data_code_len = 1404,
+		.data_punc_len = 1248,
+		.data_conv = &gsm0503_mcs5,
+		.data_punc = {
+			gsm0503_puncture_mcs5_p1,
+			gsm0503_puncture_mcs5_p2,
+			NULL,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS6,
+		.usf_len = 3,
+		.hdr_len = 25,
+		.hdr_code_len = 99,
+		.hdr_punc_len = 100,
+		.hdr_conv = &gsm0503_mcs5_dl_hdr,
+		.hdr_punc = NULL,
+
+		.data_len = 594,
+		.data_code_len = 1836,
+		.data_punc_len = 1248,
+		.data_conv = &gsm0503_mcs6,
+		.data_punc = {
+			gsm0503_puncture_mcs6_p1,
+			gsm0503_puncture_mcs6_p2,
+			NULL,
+		},
+	},
+	{
+		.mcs = EGPRS_MCS7,
+		.usf_len = 3,
+		.hdr_len = 37,
+		.hdr_code_len = 135,
+		.hdr_punc_len = 124,
+		.hdr_conv = &gsm0503_mcs7_dl_hdr,
+		.hdr_punc = gsm0503_puncture_mcs7_dl_hdr,
+
+		.data_len = 900,
+		.data_code_len = 1404,
+		.data_punc_len = 612,
+		.data_conv = &gsm0503_mcs7,
+		.data_punc = {
+			gsm0503_puncture_mcs7_p1,
+			gsm0503_puncture_mcs7_p2,
+			gsm0503_puncture_mcs7_p3,
+		}
+	},
+	{
+		.mcs = EGPRS_MCS8,
+		.usf_len = 3,
+		.hdr_len = 37,
+		.hdr_code_len = 135,
+		.hdr_punc_len = 124,
+		.hdr_conv = &gsm0503_mcs7_dl_hdr,
+		.hdr_punc = gsm0503_puncture_mcs7_dl_hdr,
+
+		.data_len = 1092,
+		.data_code_len = 1692,
+		.data_punc_len = 612,
+		.data_conv = &gsm0503_mcs8,
+		.data_punc = {
+			gsm0503_puncture_mcs8_p1,
+			gsm0503_puncture_mcs8_p2,
+			gsm0503_puncture_mcs8_p3,
+		}
+	},
+	{
+		.mcs = EGPRS_MCS9,
+		.usf_len = 3,
+		.hdr_len = 37,
+		.hdr_code_len = 135,
+		.hdr_punc_len = 124,
+		.hdr_conv = &gsm0503_mcs7_dl_hdr,
+		.hdr_punc = gsm0503_puncture_mcs7_dl_hdr,
+
+		.data_len = 1188,
+		.data_code_len = 1836,
+		.data_punc_len = 612,
+		.data_conv = &gsm0503_mcs9,
+		.data_punc = {
+			gsm0503_puncture_mcs9_p1,
+			gsm0503_puncture_mcs9_p2,
+			gsm0503_puncture_mcs9_p3,
+		}
+	},
+};
+
+static int osmo_conv_decode_ber(const struct osmo_conv_code *code,
+	const sbit_t *input, ubit_t *output,
+	int *n_errors, int *n_bits_total)
+{
+	int res, i, coded_len;
+	ubit_t recoded[EGPRS_DATA_C_MAX];
+
+	res = osmo_conv_decode(code, input, output);
+
+	if (n_bits_total || n_errors) {
+		coded_len = osmo_conv_encode(code, output, recoded);
+		OSMO_ASSERT(sizeof(recoded) / sizeof(recoded[0]) >= coded_len);
+	}
+
+	/* Count bit errors */
+	if (n_errors) {
+		*n_errors = 0;
+		for (i = 0; i < coded_len; i++) {
+			if (!((recoded[i] && input[i] < 0) ||
+					(!recoded[i] && input[i] > 0)) )
+						*n_errors += 1;
+		}
+	}
+
+	if (n_bits_total)
+		*n_bits_total = coded_len;
+
+	return res;
+}
+
+static int _xcch_decode_cB(uint8_t *l2_data, sbit_t *cB,
+	int *n_errors, int *n_bits_total)
+{
+	ubit_t conv[224];
+	int rv;
+
+	osmo_conv_decode_ber(&gsm0503_xcch, cB,
+		conv, n_errors, n_bits_total);
+
+	rv = osmo_crc64gen_check_bits(&gsm0503_fire_crc40,
+		conv, 184, conv + 184);
+	if (rv)
+		return -1;
+
+	osmo_ubit2pbit_ext(l2_data, 0, conv, 0, 184, 1);
+
+	return 0;
+}
+
+static int _xcch_encode_cB(ubit_t *cB, uint8_t *l2_data)
+{
+	ubit_t conv[224];
+
+	osmo_pbit2ubit_ext(conv, 0, l2_data, 0, 184, 1);
+
+	osmo_crc64gen_set_bits(&gsm0503_fire_crc40, conv, 184, conv + 184);
+
+	osmo_conv_encode(&gsm0503_xcch, conv, cB);
+
+	return 0;
+}
+
+/*
+ * GSM xCCH block transcoding
+ */
+int gsm0503_xcch_decode(uint8_t *l2_data, sbit_t *bursts,
+	int *n_errors, int *n_bits_total)
+{
+	sbit_t iB[456], cB[456];
+	int i;
+
+	for (i = 0; i < 4; i++)
+		gsm0503_xcch_burst_unmap(&iB[i * 114], &bursts[i * 116], NULL, NULL);
+
+	gsm0503_xcch_deinterleave(cB, iB);
+
+	return _xcch_decode_cB(l2_data, cB, n_errors, n_bits_total);
+}
+
+int gsm0503_xcch_encode(ubit_t *bursts, uint8_t *l2_data)
+{
+	ubit_t iB[456], cB[456], hl = 1, hn = 1;
+	int i;
+
+	_xcch_encode_cB(cB, l2_data);
+
+	gsm0503_xcch_interleave(cB, iB);
+
+	for (i = 0; i < 4; i++)
+		gsm0503_xcch_burst_map(&iB[i * 114], &bursts[i * 116], &hl, &hn);
+
+	return 0;
+}
+
+/*
+ * EGPRS PDTCH UL block decoding
+ */
+
+/*
+ * Type 3 - MCS-1,2,3,4
+ * Unmapping and deinterleaving
+ */
+static int egprs_type3_unmap(const sbit_t *bursts, sbit_t *hc, sbit_t *dc)
+{
+	int i;
+	sbit_t iB[456], q[8];
+
+	for (i = 0; i < 4; i++) {
+		gsm0503_xcch_burst_unmap(&iB[i * 114], &bursts[i * 116],
+			q + i * 2, q + i * 2 + 1);
+	}
+
+	gsm0503_mcs1_ul_deinterleave(hc, dc, iB);
+
+	return 0;
+}
+
+/*
+ * Type 2 - MCS-5,6
+ * Unmapping and deinterleaving
+ */
+static int egprs_type2_unmap(const sbit_t *bursts, sbit_t *hc, sbit_t *dc)
+{
+	int i;
+	sbit_t burst[348];
+	sbit_t hi[EGPRS_HDR_HC_MAX];
+	sbit_t di[EGPRS_DATA_DC_MAX];
+
+	for (i = 0; i < 4; i++) {
+		memcpy(burst, &bursts[i * 348], 348);
+
+		gsm0503_mcs5_burst_swap(burst);
+		gsm0503_mcs5_ul_burst_unmap(di, burst, hi, i);
+	}
+
+	gsm0503_mcs5_ul_deinterleave(hc, dc, hi, di);
+
+	return 0;
+}
+
+/*
+ * Type 1 - MCS-7,8,9
+ * Unmapping and deinterleaving - Note that MCS-7 interleaver is unique
+ */
+static int egprs_type1_unmap(const sbit_t *bursts, sbit_t *hc,
+	sbit_t *c1, sbit_t *c2, int msc)
+{
+	int i;
+	sbit_t burst[348];
+	sbit_t hi[EGPRS_HDR_HC_MAX];
+	sbit_t di[EGPRS_DATA_C1 * 2];
+
+	for (i = 0; i < 4; i++) {
+		memcpy(burst, &bursts[i * 348], 348);
+
+		gsm0503_mcs5_burst_swap(burst);
+		gsm0503_mcs7_ul_burst_unmap(di, burst, hi, i);
+	}
+
+	if (msc == EGPRS_MCS7)
+		gsm0503_mcs7_ul_deinterleave(hc, c1, c2, hi, di);
+	else
+		gsm0503_mcs8_ul_deinterleave(hc, c1, c2, hi, di);
+
+	return 0;
+}
+
+/*
+ * Decode EGPRS UL header section
+ *
+ * 1. Depuncture
+ * 2. Convolutional decoding
+ * 3. CRC check
+ */
+static int _egprs_decode_hdr(const sbit_t *hc, int mcs,
+	union gprs_rlc_ul_hdr_egprs *hdr)
+{
+	sbit_t C[EGPRS_HDR_C_MAX];
+	ubit_t upp[EGPRS_HDR_UPP_MAX];
+	int i, j, rc;
+	struct gsm0503_mcs_code *code;
+
+	code = &gsm0503_mcs_ul_codes[mcs];
+
+	/* Skip depuncturing on MCS-5,6 header */
+	if ((mcs == EGPRS_MCS5) || (mcs == EGPRS_MCS6)) {
+		memcpy(C, hc, code->hdr_code_len);
+		goto hdr_conv_decode;
+	}
+
+	if (!code->hdr_punc) {
+		/* Invalid MCS-X header puncture matrix */
+		return -1;
+	}
+
+	i = code->hdr_code_len - 1;
+	j = code->hdr_punc_len - 1;
+
+	for (; i >= 0; i--) {
+		if (!code->hdr_punc[i])
+			C[i] = hc[j--];
+		else
+			C[i] = 0;
+	}
+
+hdr_conv_decode:
+	osmo_conv_decode_ber(code->hdr_conv, C, upp, NULL, NULL);
+	rc = osmo_crc8gen_check_bits(&gsm0503_mcs_crc8_hdr, upp,
+		code->hdr_len, upp + code->hdr_len);
+	if (rc)
+		return -1;
+
+	osmo_ubit2pbit_ext((pbit_t *) hdr, 0, upp, 0, code->hdr_len, 1);
+
+	return 0;
+}
+
+/*
+ * Blind MCS header decoding based on burst length and CRC validation.
+ * Ignore 'q' value coding identification. This approach provides
+ * the strongest chance of header recovery.
+ */
+static int egprs_decode_hdr(union gprs_rlc_ul_hdr_egprs *hdr,
+	const sbit_t *bursts, uint16_t nbits)
+{
+	int rc;
+	sbit_t hc[EGPRS_HDR_HC_MAX];
+
+	if (nbits == GSM0503_GPRS_BURSTS_NBITS) {
+		/* MCS-1,2,3,4 */
+		egprs_type3_unmap(bursts, hc, NULL);
+		rc = _egprs_decode_hdr(hc, EGPRS_MCS1, hdr);
+		if (!rc)
+			return EGPRS_HDR_TYPE3;
+	} else if (nbits == GSM0503_EGPRS_BURSTS_NBITS) {
+		/* MCS-5,6 */
+		egprs_type2_unmap(bursts, hc, NULL);
+		rc = _egprs_decode_hdr(hc, EGPRS_MCS5, hdr);
+		if (!rc)
+			return EGPRS_HDR_TYPE2;
+
+		/* MCS-7,8,9 */
+		egprs_type1_unmap(bursts, hc, NULL, NULL, EGPRS_MCS7);
+		rc = _egprs_decode_hdr(hc, EGPRS_MCS7, hdr);
+		if (!rc)
+			return EGPRS_HDR_TYPE1;
+	}
+
+	return -1;
+}
+
+/*
+ * Parse EGPRS UL header for coding and puncturing scheme (CPS)
+ *
+ * Type 1 - MCS-7,8,9
+ * Type 2 - MCS-5,6
+ * Type 3 - MCS-1,2,3,4
+ */
+static int egprs_parse_ul_cps(struct egprs_cps *cps,
+	union gprs_rlc_ul_hdr_egprs *hdr, int type)
+{
+	uint8_t bits;
+
+	switch (type) {
+	case EGPRS_HDR_TYPE1:
+		bits = hdr->type1.cps;
+		break;
+	case EGPRS_HDR_TYPE2:
+		bits = (hdr->type2.cps_lo << 2) | hdr->type2.cps_hi;
+		break;
+	case EGPRS_HDR_TYPE3:
+		bits = (hdr->type3.cps_lo << 2) | hdr->type3.cps_hi;
+		break;
+	default:
+		return -1;
+	}
+
+	return egprs_get_cps(cps, type, bits);
+}
+
+/*
+ * Decode EGPRS UL data section
+ *
+ * 1. Depuncture
+ * 2. Convolutional decoding
+ * 3. CRC check
+ * 4. Block combining (MCS-7,8,9 only)
+ */
+static int egprs_decode_data(uint8_t *l2_data, sbit_t *c,
+	int mcs, int p, int blk, int *n_errors, int *n_bits_total)
+{
+	ubit_t u[EGPRS_DATA_U_MAX];
+	sbit_t C[EGPRS_DATA_C_MAX];
+
+	int i, j, rc, data_len;
+	struct gsm0503_mcs_code *code;
+
+	if (blk && mcs < EGPRS_MCS7) {
+		/* Invalid MCS-X block state */
+		return -1;
+	}
+
+	code = &gsm0503_mcs_ul_codes[mcs];
+	if (!code->data_punc[p]) {
+		/* Invalid MCS-X data puncture matrix */
+		return -1;
+	}
+
+	/*
+	 * MCS-1,6 - single block processing
+	 * MCS-7,9 - dual block processing
+	 */
+	if (mcs >= EGPRS_MCS7)
+		data_len = code->data_len / 2;
+	else
+		data_len = code->data_len;
+
+	i = code->data_code_len - 1;
+	j = code->data_punc_len - 1;
+
+	for (; i >= 0; i--) {
+		if (!code->data_punc[p][i])
+			C[i] = c[j--];
+		else
+			C[i] = 0;
+	}
+
+	osmo_conv_decode_ber(code->data_conv, C, u, n_errors, n_bits_total);
+	rc = osmo_crc16gen_check_bits(&gsm0503_mcs_crc12, u,
+		data_len, u + data_len);
+	if (rc)
+		return -1;
+
+	/* Offsets output pointer on the second block of Type 1 MCS */
+	osmo_ubit2pbit_ext(l2_data, code->hdr_len + blk * data_len,
+		u, 0, data_len, 1);
+
+	/* Return the number of bytes required for the bit message */
+	return NUM_BYTES(code->hdr_len + code->data_len);
+}
+
+/*
+ * Decode EGPRS UL message
+ *
+ * 1. Header section decoding
+ * 2. Extract CPS settings
+ * 3. Burst unmapping and deinterleaving
+ * 4. Data section decoding
+ */
+int gsm0503_pdtch_egprs_decode(uint8_t *l2_data, sbit_t *bursts, uint16_t nbits,
+	uint8_t *usf_p, int *n_errors, int *n_bits_total)
+{
+	sbit_t dc[EGPRS_DATA_DC_MAX];
+	sbit_t c1[EGPRS_DATA_C1], c2[EGPRS_DATA_C2];
+	int type, rc;
+	struct egprs_cps cps;
+	union gprs_rlc_ul_hdr_egprs *hdr;
+
+	if ((nbits != GSM0503_GPRS_BURSTS_NBITS) &&
+		(nbits != GSM0503_EGPRS_BURSTS_NBITS)) {
+		/* Invalid EGPRS bit length */
+		return -1;
+	}
+
+	hdr = (union gprs_rlc_ul_hdr_egprs *) l2_data;
+	type = egprs_decode_hdr(hdr, bursts, nbits);
+	if (egprs_parse_ul_cps(&cps, hdr, type) < 0)
+		return -1;
+
+	switch (cps.mcs) {
+	case EGPRS_MCS1:
+	case EGPRS_MCS2:
+	case EGPRS_MCS3:
+	case EGPRS_MCS4:
+		egprs_type3_unmap(bursts, NULL, dc);
+		break;
+	case EGPRS_MCS5:
+	case EGPRS_MCS6:
+		egprs_type2_unmap(bursts, NULL, dc);
+		break;
+	case EGPRS_MCS7:
+	case EGPRS_MCS8:
+	case EGPRS_MCS9:
+		egprs_type1_unmap(bursts, NULL, c1, c2, cps.mcs);
+		break;
+	default:
+		/* Invalid MCS-X */
+		return -1;
+	}
+
+	/* Decode MCS-X block, where X = cps.mcs */
+	if (cps.mcs < EGPRS_MCS7) {
+		rc = egprs_decode_data(l2_data, dc, cps.mcs, cps.p[0],
+			0, n_errors, n_bits_total);
+		if (rc < 0)
+			return -1;
+	} else {
+		/* MCS-7,8,9 block 1 */
+		rc = egprs_decode_data(l2_data, c1, cps.mcs, cps.p[0],
+			0, n_errors, n_bits_total);
+		if (rc < 0)
+			return -1;
+
+		/* MCS-7,8,9 block 2 */
+		rc = egprs_decode_data(l2_data, c2, cps.mcs, cps.p[1],
+			1, n_errors, n_bits_total);
+		if (rc < 0)
+			return -1;
+	}
+
+	return rc;
+}
+
+/*
+ * GSM PDTCH block transcoding
+ */
+
+int gsm0503_pdtch_decode(uint8_t *l2_data, sbit_t *bursts, uint8_t *usf_p,
+	int *n_errors, int *n_bits_total)
+{
+	sbit_t iB[456], cB[676], hl_hn[8];
+	ubit_t conv[456];
+	int i, j, k, rv, best = 0, cs = 0, usf = 0; /* make GCC happy */
+
+	for (i = 0; i < 4; i++)
+		gsm0503_xcch_burst_unmap(&iB[i * 114], &bursts[i * 116],
+			hl_hn + i * 2, hl_hn + i * 2 + 1);
+
+	for (i = 0; i < 4; i++) {
+		for (j = 0, k = 0; j < 8; j++)
+			k += abs(((int)gsm0503_pdtch_hl_hn_sbit[i][j]) - ((int)hl_hn[j]));
+
+		if (i == 0 || k < best) {
+			best = k;
+			cs = i + 1;
+		}
+	}
+
+	gsm0503_xcch_deinterleave(cB, iB);
+
+	switch (cs) {
+	case 1:
+		osmo_conv_decode_ber(&gsm0503_xcch, cB,
+			conv, n_errors, n_bits_total);
+
+		rv = osmo_crc64gen_check_bits(&gsm0503_fire_crc40,
+			conv, 184, conv + 184);
+		if (rv)
+			return -1;
+
+		osmo_ubit2pbit_ext(l2_data, 0, conv, 0, 184, 1);
+
+		return 23;
+	case 2:
+		for (i = 587, j = 455; i >= 0; i--) {
+			if (!gsm0503_puncture_cs2[i])
+				cB[i] = cB[j--];
+			else
+				cB[i] = 0;
+		}
+
+		osmo_conv_decode_ber(&gsm0503_cs2_np, cB,
+			conv, n_errors, n_bits_total);
+
+		for (i = 0; i < 8; i++) {
+			for (j = 0, k = 0; j < 6; j++)
+				k += abs(((int)gsm0503_usf2six[i][j]) - ((int)conv[j]));
+
+			if (i == 0 || k < best) {
+				best = k;
+				usf = i;
+			}
+		}
+
+		conv[3] = usf & 1;
+		conv[4] = (usf >> 1) & 1;
+		conv[5] = (usf >> 2) & 1;
+		if (usf_p)
+			*usf_p = usf;
+
+		rv = osmo_crc16gen_check_bits(&gsm0503_cs234_crc16,
+			conv + 3, 271, conv + 3 + 271);
+		if (rv)
+			return -1;
+
+		osmo_ubit2pbit_ext(l2_data, 0, conv, 3, 271, 1);
+
+		return 34;
+	case 3:
+		for (i = 675, j = 455; i >= 0; i--) {
+			if (!gsm0503_puncture_cs3[i])
+				cB[i] = cB[j--];
+			else
+				cB[i] = 0;
+		}
+
+		osmo_conv_decode_ber(&gsm0503_cs3_np, cB,
+			conv, n_errors, n_bits_total);
+
+		for (i = 0; i < 8; i++) {
+			for (j = 0, k = 0; j < 6; j++)
+				k += abs(((int)gsm0503_usf2six[i][j]) - ((int)conv[j]));
+
+			if (i == 0 || k < best) {
+				best = k;
+				usf = i;
+			}
+		}
+
+		conv[3] = usf & 1;
+		conv[4] = (usf >> 1) & 1;
+		conv[5] = (usf >> 2) & 1;
+		if (usf_p)
+			*usf_p = usf;
+
+		rv = osmo_crc16gen_check_bits(&gsm0503_cs234_crc16,
+			conv + 3, 315, conv + 3 + 315);
+		if (rv)
+			return -1;
+
+		osmo_ubit2pbit_ext(l2_data, 0, conv, 3, 315, 1);
+
+		return 40;
+	case 4:
+		for (i = 12; i < 456; i++)
+			conv[i] = (cB[i] < 0) ? 1 : 0;
+
+		for (i = 0; i < 8; i++) {
+			for (j = 0, k = 0; j < 12; j++)
+				k += abs(((int)gsm0503_usf2twelve_sbit[i][j]) - ((int)cB[j]));
+
+			if (i == 0 || k < best) {
+				best = k;
+				usf = i;
+			}
+		}
+
+		conv[9] = usf & 1;
+		conv[10] = (usf >> 1) & 1;
+		conv[11] = (usf >> 2) & 1;
+		if (usf_p)
+			*usf_p = usf;
+
+		rv = osmo_crc16gen_check_bits(&gsm0503_cs234_crc16,
+			conv + 9, 431, conv + 9 + 431);
+		if (rv) {
+			*n_bits_total = 456 - 12;
+			*n_errors = *n_bits_total;
+			return -1;
+		}
+
+		*n_bits_total = 456 - 12;
+		*n_errors = 0;
+
+		osmo_ubit2pbit_ext(l2_data, 0, conv, 9, 431, 1);
+
+		return 54;
+	default:
+		*n_bits_total = 0;
+		*n_errors = 0;
+		break;
+	}
+
+	return -1;
+}
+
+/*
+ * EGPRS PDTCH UL block encoding
+ */
+static int egprs_type3_map(ubit_t *bursts, ubit_t *hc, ubit_t *dc, int usf)
+{
+	int i;
+	ubit_t iB[456];
+	const ubit_t *hl_hn = gsm0503_pdtch_hl_hn_ubit[3];
+
+	gsm0503_mcs1_dl_interleave(gsm0503_usf2six[usf], hc, dc, iB);
+
+	for (i = 0; i < 4; i++) {
+		gsm0503_xcch_burst_map(&iB[i * 114], &bursts[i * 116],
+			hl_hn + i * 2, hl_hn + i * 2 + 1);
+	}
+
+	return 0;
+}
+
+static int egprs_type2_map(ubit_t *bursts, ubit_t *hc, ubit_t *dc, int usf)
+{
+	int i;
+	const ubit_t *up;
+	ubit_t hi[EGPRS_HDR_HC_MAX];
+	ubit_t di[EGPRS_DATA_DC_MAX];
+
+	gsm0503_mcs5_dl_interleave(hc, dc, hi, di);
+	up = gsm0503_mcs5_usf_precode_table[usf];
+
+	for (i = 0; i < 4; i++) {
+		gsm0503_mcs5_dl_burst_map(di, &bursts[i * 348], hi, up, i);
+		gsm0503_mcs5_burst_swap((sbit_t *) &bursts[i * 348]);
+	}
+
+	return 0;
+}
+
+static int egprs_type1_map(ubit_t *bursts, ubit_t *hc,
+	ubit_t *c1, ubit_t *c2, int usf, int mcs)
+{
+	int i;
+	const ubit_t *up;
+	ubit_t hi[EGPRS_HDR_HC_MAX];
+	ubit_t di[EGPRS_DATA_C1 * 2];
+
+	if (mcs == EGPRS_MCS7)
+		gsm0503_mcs7_dl_interleave(hc, c1, c2, hi, di);
+	else
+		gsm0503_mcs8_dl_interleave(hc, c1, c2, hi, di);
+
+	up = gsm0503_mcs5_usf_precode_table[usf];
+
+	for (i = 0; i < 4; i++) {
+		gsm0503_mcs7_dl_burst_map(di, &bursts[i * 348], hi, up, i);
+		gsm0503_mcs5_burst_swap((sbit_t *) &bursts[i * 348]);
+	}
+
+	return 0;
+}
+
+static int egprs_encode_hdr(ubit_t *hc, uint8_t *l2_data, int mcs)
+{
+	int i, j;
+	ubit_t upp[EGPRS_HDR_UPP_MAX], C[EGPRS_HDR_C_MAX];
+	struct gsm0503_mcs_code *code;
+
+	code = &gsm0503_mcs_dl_codes[mcs];
+
+	osmo_pbit2ubit_ext(upp, 0, l2_data, code->usf_len, code->hdr_len, 1);
+	osmo_crc8gen_set_bits(&gsm0503_mcs_crc8_hdr, upp,
+		code->hdr_len, upp + code->hdr_len);
+
+	osmo_conv_encode(code->hdr_conv, upp, C);
+
+	/* MCS-5,6 header direct puncture instead of table */
+	if ((mcs == EGPRS_MCS5) || (mcs == EGPRS_MCS6)) {
+		memcpy(hc, C, code->hdr_code_len);
+		hc[99] = hc[98];
+		return 0;
+	}
+
+	if (!code->hdr_punc) {
+		/* Invalid MCS-X header puncture matrix */
+		return -1;
+	}
+
+	for (i = 0, j = 0; i < code->hdr_code_len; i++) {
+		if (!code->hdr_punc[i])
+			hc[j++] = C[i];
+	}
+
+	return 0;
+}
+
+static int egprs_encode_data(ubit_t *c, uint8_t *l2_data,
+	int mcs, int p, int blk)
+{
+	int i, j, data_len;
+	ubit_t u[EGPRS_DATA_U_MAX], C[EGPRS_DATA_C_MAX];
+	struct gsm0503_mcs_code *code;
+
+	code = &gsm0503_mcs_dl_codes[mcs];
+
+	/*
+	 * Dual block   - MCS-7,8,9
+	 * Single block - MCS-1,2,3,4,5,6
+	 */
+	if (mcs >= EGPRS_MCS7)
+		data_len = code->data_len / 2;
+	else
+		data_len = code->data_len;
+
+	osmo_pbit2ubit_ext(u, 0, l2_data,
+		code->usf_len + code->hdr_len + blk * data_len, data_len, 1);
+
+	osmo_crc16gen_set_bits(&gsm0503_mcs_crc12, u, data_len, u + data_len);
+
+	osmo_conv_encode(code->data_conv, u, C);
+
+	if (!code->data_punc[p]) {
+		/* Invalid MCS-X data puncture matrix */
+		return -1;
+	}
+
+	for (i = 0, j = 0; i < code->data_code_len; i++) {
+		if (!code->data_punc[p][i])
+			c[j++] = C[i];
+	}
+
+	return 0;
+}
+
+/*
+ * Parse EGPRS DL header for coding and puncturing scheme (CPS)
+ *
+ * Type 1 - MCS-7,8,9
+ * Type 2 - MCS-5,6
+ * Type 3 - MCS-1,2,3,4
+ */
+static int egprs_parse_dl_cps(struct egprs_cps *cps,
+	union gprs_rlc_dl_hdr_egprs *hdr, int type)
+{
+	uint8_t bits;
+
+	switch (type) {
+	case EGPRS_HDR_TYPE1:
+		bits = hdr->type1.cps;
+		break;
+	case EGPRS_HDR_TYPE2:
+		bits = hdr->type2.cps;
+		break;
+	case EGPRS_HDR_TYPE3:
+		bits = hdr->type3.cps;
+		break;
+	default:
+		return -1;
+	}
+
+	return egprs_get_cps(cps, type, bits);
+}
+
+/*
+ * EGPRS DL message encoding
+ */
+int gsm0503_pdtch_egprs_encode(ubit_t *bursts,
+	uint8_t *l2_data, uint8_t l2_len)
+{
+	ubit_t hc[EGPRS_DATA_C_MAX], dc[EGPRS_DATA_DC_MAX];
+	ubit_t c1[EGPRS_DATA_C1], c2[EGPRS_DATA_C2];