+/*
+ * 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>
+
+void
+ao_fec_dump_bytes(uint8_t *bytes, uint8_t len, char *name)
+{
+ uint8_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");
+}
+
+static uint16_t inline
+crc_byte(uint8_t byte, uint16_t crc)
+{
+ uint8_t bit;
+
+ for (bit = 0; bit < 8; bit++) {
+ if (((crc & 0x8000) >> 8) ^ (byte & 0x80))
+ crc = (crc << 1) ^ 0x8005;
+ else
+ crc = (crc << 1);
+ byte <<= 1;
+ }
+ return crc;
+}
+
+uint16_t
+ao_fec_crc(uint8_t *bytes, uint8_t len)
+{
+ uint16_t crc = AO_FEC_CRC_INIT;
+
+ while (len--)
+ crc = crc_byte(*bytes++, crc);
+ return crc;
+}
+
+uint8_t
+ao_fec_prepare(uint8_t *in, uint8_t len, uint8_t *out)
+{
+ uint16_t crc = ao_fec_crc (in, len);
+ uint8_t i;
+ uint8_t num_fec;
+
+ /* Copy data */
+ for (i = 0; i < len; i++)
+ out[i] = in[i];
+
+ /* Append CRC */
+ out[i++] = crc >> 8;
+ out[i++] = crc;
+
+ /* Append FEC -- 1 byte if odd, two bytes if even */
+ num_fec = 2 - (i & 1);
+ while (num_fec--)
+ out[i++] = AO_FEC_TRELLIS_TERMINATOR;
+ return i;
+}
+
+static const uint8_t whiten[] = {
+#include "ao_whiten.h"
+};
+
+uint8_t
+ao_fec_whiten(uint8_t *in, uint8_t len, uint8_t *out)
+{
+ const uint8_t *w = whiten;
+
+ while (len--)
+ *out++ = *in++ ^ *w++;
+}
+
+static const uint8_t ao_fec_encode_table[16] = {
+ 0, 3, 1, 2,
+ 3, 0, 2, 1,
+ 3, 0, 2, 1,
+ 0, 3, 1, 2
+};
+
+uint8_t
+ao_fec_encode(uint8_t *in, uint8_t len, uint8_t *out)
+{
+ uint16_t fec = 0, output;
+ uint8_t byte, bit;
+
+ for (byte = 0; byte < len; byte++) {
+ fec = (fec & 0x700) | in[byte];
+ output = 0;
+ for (bit = 0; bit < 8; bit++) {
+ output = output << 2 | ao_fec_encode_table[fec >> 7];
+ fec = (fec << 1) & 0x7ff;
+ }
+ out[byte * 2] = output >> 8;
+ out[byte * 2 + 1] = output;
+ }
+ return len * 2;
+}
+
+uint8_t
+ao_fec_interleave(uint8_t *in, uint8_t len, uint8_t *out)
+{
+ uint8_t i, j;
+
+ for (i = 0; i < len; i += 4) {
+ uint32_t interleaved = 0;
+
+ for (j = 0; j < 4 * 4; j++) {
+ interleaved <<= 2;
+ interleaved |= (in[i + (~j & 0x3)] >> (2 * ((j & 0xc) >> 2))) & 0x03;
+ }
+ out[i+0] = interleaved >> 24;
+ out[i+1] = interleaved >> 16;
+ out[i+2] = interleaved >> 8;
+ out[i+3] = interleaved;
+ }
+ return len;
+}