altos: Optimize FEC encode and decode

[fw/altos] / src / core / ao_fec_tx.c

diff --git a/src/core/ao_fec_tx.c b/src/core/ao_fec_tx.c
index c9c0a3d6c98310ba26f170e5ab60782b246a3667..4941d74581254ec26402218b9ed952cdbc03138b 100644 (file)
--- a/src/core/ao_fec_tx.c
+++ b/src/core/ao_fec_tx.c
@@ -18,8 +18,9 @@
 #include <ao_fec.h>
 #include <stdio.h>
 
+#if AO_FEC_DEBUG
 void
-ao_fec_dump_bytes(uint8_t *bytes, uint16_t len, char *name)
+ao_fec_dump_bytes(const uint8_t *bytes, uint16_t len, const char *name)
 {
        uint16_t        i;
 
@@ -31,29 +32,15 @@ ao_fec_dump_bytes(uint8_t *bytes, uint16_t len, char *name)
        }
        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;
-}
+#endif
 
 uint16_t
-ao_fec_crc(uint8_t *bytes, uint8_t len)
+ao_fec_crc(const uint8_t *bytes, uint8_t len)
 {
        uint16_t        crc = AO_FEC_CRC_INIT;
 
        while (len--)
-               crc = crc_byte(*bytes++, crc);
+               crc = ao_fec_crc_byte(*bytes++, crc);
        return crc;
 }
 
@@ -63,7 +50,7 @@ ao_fec_crc(uint8_t *bytes, uint8_t len)
  */
 
 uint8_t
-ao_fec_check_crc(uint8_t *bytes, uint8_t len)
+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]);
@@ -71,8 +58,11 @@ ao_fec_check_crc(uint8_t *bytes, uint8_t len)
        return computed_crc == received_crc;
 }
 
-uint8_t
-ao_fec_prepare(uint8_t *in, uint8_t len, uint8_t *extra)
+/*
+ * 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;
@@ -93,40 +83,6 @@ const uint8_t ao_fec_whiten_table[] = {
 #include "ao_whiten.h"
 };
 
-#if 0
-void
-ao_fec_whiten(uint8_t *in, uint8_t len, uint8_t *out)
-{
-       const uint8_t   *w = ao_fec_whiten_table;
-
-       while (len--)
-               *out++ = *in++ ^ *w++;
-}
-
-/*
- * Unused as interleaving is now built in to ao_fec_encode
- */
-
-static void
-ao_fec_interleave(uint8_t *d, uint8_t len)
-{
-       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 |= (d[i + (~j & 0x3)] >> (2 * ((j & 0xc) >> 2))) & 0x03;
-               }
-               d[i+0] = interleaved >> 24;
-               d[i+1] = interleaved >> 16;
-               d[i+2] = interleaved >> 8;
-               d[i+3] = interleaved;
-       }
-}
-#endif
-
 static const uint8_t ao_fec_encode_table[16] = {
 /* next 0  1     state */
        0, 3,   /* 000 */
@@ -140,7 +96,7 @@ static const uint8_t ao_fec_encode_table[16] = {
 };
 
 uint8_t
-ao_fec_encode(uint8_t *in, uint8_t len, uint8_t *out)
+ao_fec_encode(const uint8_t *in, uint8_t len, uint8_t *out)
 {
        uint8_t         extra[AO_FEC_PREPARE_EXTRA];
        uint8_t         extra_len;