altos: Incremental viterbi decode

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

diff --git a/src/core/ao_viterbi.c b/src/core/ao_viterbi.c
index 594c0d91bdbf51be2e79180ba7f639ba2d615df2..69e9c1f5b7da393f9757e9b88b6448a1cf95b31d 100644 (file)
--- a/src/core/ao_viterbi.c
+++ b/src/core/ao_viterbi.c
@@ -91,7 +91,7 @@ ao_cost(struct ao_soft_sym a, struct ao_soft_sym b)
  */
 
 uint8_t
-ao_fec_decode(uint8_t *in, uint16_t len, uint8_t *out)
+ao_fec_decode(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 uint16_t bits[2][NUM_STATE];             /* save bits to quickly output them */
@@ -105,6 +105,7 @@ ao_fec_decode(uint8_t *in, uint16_t len, uint8_t *out)
        const uint8_t   *whiten = ao_fec_whiten_table;
        uint16_t        interleave;                     /* input byte array index */
        struct ao_soft_sym      s;                      /* input symbol pair */
+       uint16_t        avail;
 
        p = 0;
        for (state = 0; state < NUM_STATE; state++) {
@@ -113,11 +114,22 @@ ao_fec_decode(uint8_t *in, uint16_t len, uint8_t *out)
        }
        cost[0][0] = 0;
 
+       if (callback)
+               avail = 0;
+       else
+               avail = len;
+
        o = 0;
        for (i = 0; i < len; i += 2) {
                b = i/2;
                n = p ^ 1;
 
+               if (!avail) {
+                       avail = callback();
+                       if (!avail)
+                               break;
+               }
+
                /* Fetch one pair of input bytes, de-interleaving
                 * the input.
                 */
@@ -203,7 +215,10 @@ ao_fec_decode(uint8_t *in, uint16_t len, uint8_t *out)
                        printf ("\tbit %3d min_cost %5d old bit %3d old_state %x bits %02x whiten %0x\n",
                                i/2, min_cost, o + 8, min_state, (bits[p][min_state] >> dist) & 0xff, *whiten);
 #endif
-                       *out++ = (bits[p][min_state] >> dist) ^ *whiten++;
+                       if (out_len) {
+                               *out++ = (bits[p][min_state] >> dist) ^ *whiten++;
+                               --out_len;
+                       }
                        o += 8;
                }
        }