diff options
Diffstat (limited to 'src/core/ao_fec_tx.c')
| -rw-r--r-- | src/core/ao_fec_tx.c | 118 |
1 files changed, 76 insertions, 42 deletions
diff --git a/src/core/ao_fec_tx.c b/src/core/ao_fec_tx.c index c5f410b8..c9c0a3d6 100644 --- a/src/core/ao_fec_tx.c +++ b/src/core/ao_fec_tx.c @@ -19,9 +19,9 @@ #include <stdio.h> void -ao_fec_dump_bytes(uint8_t *bytes, uint8_t len, char *name) +ao_fec_dump_bytes(uint8_t *bytes, uint16_t len, char *name) { - uint8_t i; + uint16_t i; printf ("%s (%d):", name, len); for (i = 0; i < len; i++) { @@ -57,41 +57,76 @@ ao_fec_crc(uint8_t *bytes, uint8_t len) return crc; } +/* + * len is the length of the data; the crc will be + * the fist two bytes after that + */ + uint8_t -ao_fec_prepare(uint8_t *in, uint8_t len, uint8_t *out) +ao_fec_check_crc(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; +} + +uint8_t +ao_fec_prepare(uint8_t *in, uint8_t len, uint8_t *extra) { uint16_t crc = ao_fec_crc (in, len); - uint8_t i; + uint8_t i = 0; 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; + 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--) - out[i++] = AO_FEC_TRELLIS_TERMINATOR; + extra[i++] = AO_FEC_TRELLIS_TERMINATOR; return i; } -static const uint8_t whiten[] = { +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 = whiten; + 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 */ @@ -107,38 +142,37 @@ static const uint8_t ao_fec_encode_table[16] = { 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; + 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; + } } - 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; + interleave = 0; + for (bit = 0; bit < 4 * 4; bit++) { + uint8_t byte_shift = (bit & 0x3) << 3; + uint8_t bit_shift = (bit & 0xc) >> 1; - for (j = 0; j < 4 * 4; j++) { - interleaved <<= 2; - interleaved |= (in[i + (~j & 0x3)] >> (2 * ((j & 0xc) >> 2))) & 0x03; + interleave = (interleave << 2) | ((encode >> (byte_shift + bit_shift)) & 0x3); } - out[i+0] = interleaved >> 24; - out[i+1] = interleaved >> 16; - out[i+2] = interleaved >> 8; - out[i+3] = interleaved; + *out++ = interleave >> 24; + *out++ = interleave >> 16; + *out++ = interleave >> 8; + *out++ = interleave >> 0; } - return len; + return (len + extra_len) * 2; } |