X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=blobdiff_plain;f=src%2Fkernel%2Fao_fec_tx.c;fp=src%2Fkernel%2Fao_fec_tx.c;h=4941d74581254ec26402218b9ed952cdbc03138b;hp=0000000000000000000000000000000000000000;hb=24167015705ae831692b95735968b04a876f935e;hpb=bb9fdef607728cc326a82aa632e59724f272e53b

diff --git a/src/kernel/ao_fec_tx.c b/src/kernel/ao_fec_tx.c
new file mode 100644
index 00000000..4941d745
--- /dev/null
+++ b/src/kernel/ao_fec_tx.c
@@ -0,0 +1,134 @@
+/*
+ * Copyright © 2012 Keith Packard <keithp@keithp.com>
+ *
+ * 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; version 2 of the License.
+ *
+ * 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.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include <ao_fec.h>
+#include <stdio.h>
+
+#if AO_FEC_DEBUG
+void
+ao_fec_dump_bytes(const uint8_t *bytes, uint16_t len, const char *name)
+{
+	uint16_t	i;
+
+	printf ("%s (%d):", name, len);
+	for (i = 0; i < len; i++) {
+		if ((i & 7) == 0)
+			printf ("\n\t%02x:", i);
+		printf(" %02x", bytes[i]);
+	}
+	printf ("\n");
+}
+#endif
+
+uint16_t
+ao_fec_crc(const uint8_t *bytes, uint8_t len)
+{
+	uint16_t	crc = AO_FEC_CRC_INIT;
+
+	while (len--)
+		crc = ao_fec_crc_byte(*bytes++, crc);
+	return crc;
+}
+
+/*
+ * len is the length of the data; the crc will be
+ * the fist two bytes after that
+ */
+
+uint8_t
+ao_fec_check_crc(const uint8_t *bytes, uint8_t len)
+{
+	uint16_t	computed_crc = ao_fec_crc(bytes, len);
+	uint16_t	received_crc = (bytes[len] << 8) | (bytes[len+1]);
+
+	return computed_crc == received_crc;
+}
+
+/*
+ * Compute CRC and trellis-terminator/interleave-pad bytes
+ */
+static uint8_t
+ao_fec_prepare(const uint8_t *in, uint8_t len, uint8_t *extra)
+{
+	uint16_t	crc = ao_fec_crc (in, len);
+	uint8_t		i = 0;
+	uint8_t		num_fec;
+
+	/* Append CRC */
+	extra[i++] = crc >> 8;
+	extra[i++] = crc;
+
+	/* Append FEC -- 1 byte if odd, two bytes if even */
+	num_fec = 2 - (i & 1);
+	while (num_fec--)
+		extra[i++] = AO_FEC_TRELLIS_TERMINATOR;
+	return i;
+}
+
+const uint8_t ao_fec_whiten_table[] = {
+#include "ao_whiten.h"
+};
+
+static const uint8_t ao_fec_encode_table[16] = {
+/* next 0  1	  state */
+	0, 3,	/* 000 */
+	1, 2,	/* 001 */
+	3, 0,	/* 010 */
+	2, 1,	/* 011 */
+	3, 0,	/* 100 */
+	2, 1,	/* 101 */
+	0, 3,	/* 110 */
+	1, 2	/* 111 */
+};
+
+uint8_t
+ao_fec_encode(const uint8_t *in, uint8_t len, uint8_t *out)
+{
+	uint8_t		extra[AO_FEC_PREPARE_EXTRA];
+	uint8_t 	extra_len;
+	uint32_t	encode, interleave;
+	uint8_t		pair, byte, bit;
+	uint16_t	fec = 0;
+	const uint8_t	*whiten = ao_fec_whiten_table;
+
+	extra_len = ao_fec_prepare(in, len, extra);
+	for (pair = 0; pair < len + extra_len; pair += 2) {
+		encode = 0;
+		for (byte = 0; byte < 2; byte++) {
+			if (pair + byte == len)
+				in = extra;
+			fec |= *in++ ^ *whiten++;
+			for (bit = 0; bit < 8; bit++) {
+				encode = encode << 2 | ao_fec_encode_table[fec >> 7];
+				fec = (fec << 1) & 0x7ff;
+			}
+		}
+
+		interleave = 0;
+		for (bit = 0; bit < 4 * 4; bit++) {
+			uint8_t	byte_shift = (bit & 0x3) << 3;
+			uint8_t	bit_shift = (bit & 0xc) >> 1;
+
+			interleave = (interleave << 2) | ((encode >> (byte_shift + bit_shift)) & 0x3);
+		}
+		*out++ = interleave >> 24;
+		*out++ = interleave >> 16;
+		*out++ = interleave >> 8;
+		*out++ = interleave >> 0;
+	}
+	return (len + extra_len) * 2;
+}