#include <ao_fec.h>
#include <stdio.h>
+#ifdef MEGAMETRUM
+#include <ao.h>
+#endif
+
+#if AO_PROFILE
+#include <ao_profile.h>
+
+uint32_t ao_fec_decode_start, ao_fec_decode_end;
+#endif
+
/*
* byte order repeats through 3 2 1 0
*
* 18/19 10/11 08/09 00/01
*/
+static const uint8_t ao_interleave_order[] = {
+ 0x1e, 0x16, 0x0e, 0x06,
+ 0x1c, 0x14, 0x0c, 0x04,
+ 0x1a, 0x12, 0x0a, 0x02,
+ 0x18, 0x10, 0x08, 0x00
+};
+
static inline uint16_t ao_interleave_index(uint16_t i) {
- uint8_t l = i & 0x1e;
- uint16_t h = i & ~0x1e;
- uint8_t o = 0x1e ^ (((l >> 2) & 0x6) | ((l << 2) & 0x18));
- return h | o;
+ return (i & ~0x1e) | ao_interleave_order[(i & 0x1e) >> 1];
}
-struct ao_soft_sym {
- uint8_t a, b;
-};
-
#define NUM_STATE 8
#define NUM_HIST 8
-#define MOD_HIST(b) ((b) & 7)
-
-#define V_0 0xc0
-#define V_1 0x40
-
-static const struct ao_soft_sym ao_fec_decode_table[NUM_STATE][2] = {
-/* next 0 1 state */
- { { V_0, V_0 }, { V_1, V_1 } } , /* 000 */
- { { V_0, V_1 }, { V_1, V_0 } }, /* 001 */
- { { V_1, V_1 }, { V_0, V_0 } }, /* 010 */
- { { V_1, V_0 }, { V_0, V_1 } }, /* 011 */
- { { V_1, V_1 }, { V_0, V_0 } }, /* 100 */
- { { V_1, V_0 }, { V_0, V_1 } }, /* 101 */
- { { V_0, V_0 }, { V_1, V_1 } }, /* 110 */
- { { V_0, V_1 }, { V_1, V_0 } } /* 111 */
+
+#define V_0 0xff
+#define V_1 0x00
+
+/*
+ * These are just the 'zero' states; the 'one' states mirror them
+ */
+static const uint8_t ao_fec_decode_table[NUM_STATE*2] = {
+ V_0, V_0, /* 000 */
+ V_0, V_1, /* 001 */
+ V_1, V_1, /* 010 */
+ V_1, V_0, /* 011 */
+ V_1, V_1, /* 100 */
+ V_1, V_0, /* 101 */
+ V_0, V_0, /* 110 */
+ V_0, V_1 /* 111 */
};
static inline uint8_t
return ((state << 1) | bit) & 0x7;
}
-static inline uint16_t ao_abs(int16_t x) { return x < 0 ? -x : x; }
-
-static inline uint16_t
-ao_cost(struct ao_soft_sym a, struct ao_soft_sym b)
-{
- return ao_abs(a.a - b.a) + ao_abs(a.b - b.b);
-}
-
/*
* 'in' is 8-bits per symbol soft decision data
* 'len' is input byte length. 'out' must be
*/
uint8_t
-ao_fec_decode(uint8_t *in, uint16_t len, uint8_t *out, uint8_t out_len, uint16_t (*callback)())
+ao_fec_decode(const uint8_t *in, uint16_t len, uint8_t *out, uint8_t out_len, uint16_t (*callback)())
{
- static uint16_t cost[2][NUM_STATE]; /* path cost */
+ static uint32_t cost[2][NUM_STATE]; /* path cost */
static uint16_t bits[2][NUM_STATE]; /* save bits to quickly output them */
+
uint16_t i; /* input byte index */
uint16_t b; /* encoded symbol index (bytes/2) */
uint16_t o; /* output bit index */
uint8_t p; /* previous cost/bits index */
uint8_t n; /* next cost/bits index */
uint8_t state; /* state index */
- uint8_t bit; /* original encoded bit index */
const uint8_t *whiten = ao_fec_whiten_table;
uint16_t interleave; /* input byte array index */
- struct ao_soft_sym s; /* input symbol pair */
+ uint8_t s0, s1;
uint16_t avail;
+ uint16_t crc = AO_FEC_CRC_INIT;
+#if AO_PROFILE
+ uint32_t start_tick;
+#endif
p = 0;
for (state = 0; state < NUM_STATE; state++) {
- cost[0][state] = 0xffff;
+ cost[0][state] = 0x7fffffff;
bits[0][state] = 0;
}
cost[0][0] = 0;
else
avail = len;
+#if AO_PROFILE
+ if (!avail) {
+ avail = callback();
+ if (!avail)
+ return 0;
+ }
+ start_tick = ao_profile_tick();
+#endif
o = 0;
for (i = 0; i < len; i += 2) {
b = i/2;
if (!avail) {
avail = callback();
if (!avail)
- break;
+ return 0;
}
/* Fetch one pair of input bytes, de-interleaving
* the input.
*/
interleave = ao_interleave_index(i);
- s.a = in[interleave];
- s.b = in[interleave+1];
+ s0 = in[interleave];
+ s1 = in[interleave+1];
+
+ avail -= 2;
/* Reset next costs to 'impossibly high' values so that
* the first path through this state is cheaper than this
*/
for (state = 0; state < NUM_STATE; state++)
- cost[n][state] = 0xffff;
+ cost[n][state] = 0x7fffffff;
/* Compute path costs and accumulate output bit path
* for each state and encoded bit value
*/
for (state = 0; state < NUM_STATE; state++) {
- for (bit = 0; bit < 2; bit++) {
- int bit_cost = cost[p][state] + ao_cost(s, ao_fec_decode_table[state][bit]);
- uint8_t bit_state = ao_next_state(state, bit);
-
- /* Only track the minimal cost to reach
- * this state; the best path can never
- * go through the higher cost paths as
- * total path cost is cumulative
- */
- if (bit_cost < cost[n][bit_state]) {
- cost[n][bit_state] = bit_cost;
- bits[n][bit_state] = (bits[p][state] << 1) | (state & 1);
+ uint32_t bitcost = ((uint32_t) (s0 ^ ao_fec_decode_table[(state<<1)]) +
+ (uint32_t) (s1 ^ ao_fec_decode_table[(state<<1)+1]));
+ {
+ uint32_t cost0 = cost[p][state] + bitcost;
+ uint8_t state0 = ao_next_state(state, 0);
+
+ if (cost0 < cost[n][state0]) {
+ cost[n][state0] = cost0;
+ bits[n][state0] = (bits[p][state] << 1) | (state & 1);
+ }
+ }
+ {
+ uint32_t cost1 = cost[p][state] + 510 - bitcost;
+ uint8_t state1 = ao_next_state(state, 1);
+
+ if (cost1 < cost[n][state1]) {
+ cost[n][state1] = cost1;
+ bits[n][state1] = (bits[p][state] << 1) | (state & 1);
}
}
}
#if 0
- printf ("bit %3d symbol %2x %2x:", i/2, s.a, s.b);
+ printf ("bit %3d symbol %2x %2x:", i/2, s0, s1);
for (state = 0; state < NUM_STATE; state++) {
printf (" %5d(%04x)", cost[n][state], bits[n][state]);
}
* it will be seven.
*/
int8_t dist = b - (o + 8); /* distance to last ready-for-writing bit */
- uint16_t min_cost; /* lowest cost */
+ uint32_t min_cost; /* lowest cost */
uint8_t min_state; /* lowest cost state */
/* Find the best fit at the current point
i/2, min_cost, o + 8, min_state, (bits[p][min_state] >> dist) & 0xff, *whiten);
#endif
if (out_len) {
- *out++ = (bits[p][min_state] >> dist) ^ *whiten++;
+ uint8_t byte = (bits[p][min_state] >> dist) ^ *whiten++;
+
+ if (out_len > 2) {
+ crc = ao_fec_crc_byte(byte, crc);
+ *out++ = byte;
+ } else {
+ *out++ = byte ^ (crc >> 8);
+ crc <<= 8;
+ }
--out_len;
}
o += 8;
}
}
+#if AO_PROFILE
+ ao_fec_decode_start = start_tick;
+ ao_fec_decode_end = ao_profile_tick();
+#endif
return len/16;
}