/*
* Parse stream headers until a compressed block or end of stream is reached. Possible return codes: OK - a
* compressed block was found FINISH - end of stream was reached MORE - more input is need, parsing was suspended
* ERR_HEADER - invalid stream header ERR_STRMCRC - stream CRC does not match ERR_EOF - unterminated stream (EOF
* reached before end of stream) garbage is set only when returning FINISH. It is number of garbage bits consumed
* after end of stream was reached.
*/
Status parse(Header hd, BitStream bs, int[] garbage) throws StreamFormatException {
assert (state != ACCEPT);
while (OK == bs.need(16)) {
int word = bs.peek(16);
bs.dump(16);
switch (state) {
case STREAM_MAGIC_1:
if (0x425A != word) {
hd.bs100k = -1;
hd.crc = 0;
state = ACCEPT;
garbage[0] = 16;
return FINISH;
}
state = STREAM_MAGIC_2;
continue;
case STREAM_MAGIC_2:
if (0x6839 < word || 0x6831 > word) {
hd.bs100k = -1;
hd.crc = 0;
state = ACCEPT;
garbage[0] = 32;
return FINISH;
}
bs100k = word & 0xF;
state = BLOCK_MAGIC_1;
continue;
case BLOCK_MAGIC_1:
if (0x1772 == word) {
state = EOS_2;
continue;
}
if (0x3141 != word) throw new StreamFormatException("ERR_HEADER");
state = BLOCK_MAGIC_2;
continue;
case BLOCK_MAGIC_2:
if (0x5926 != word) throw new StreamFormatException("ERR_HEADER");
state = BLOCK_MAGIC_3;
continue;
case BLOCK_MAGIC_3:
if (0x5359 != word) throw new StreamFormatException("ERR_HEADER");
state = BLOCK_CRC_1;
continue;
case BLOCK_CRC_1:
stored_crc = word;
state = BLOCK_CRC_2;
continue;
case BLOCK_CRC_2:
hd.crc = (stored_crc << 16) | word;
hd.bs100k = bs100k;
computed_crc = (computed_crc << 1) ^ (computed_crc >>> 31) ^ hd.crc;
state = BLOCK_MAGIC_1;
return OK;
case EOS_2:
if (0x4538 != word) throw new StreamFormatException("ERR_HEADER");
state = EOS_3;
continue;
case EOS_3:
if (0x5090 != word) throw new StreamFormatException("ERR_HEADER");
state = EOS_CRC_1;
continue;
case EOS_CRC_1:
stored_crc = word;
state = EOS_CRC_2;
continue;
case EOS_CRC_2:
stored_crc = (stored_crc << 16) | word;
if (stored_crc != computed_crc) throw new StreamFormatException("ERR_STRMCRC");
computed_crc = 0;
bs.align();
state = STREAM_MAGIC_1;
continue;
default:
break;
}
throw new IllegalStateException();
}
if (FINISH != bs.need(16)) return MORE;
if (state == STREAM_MAGIC_1) {
state = ACCEPT;
garbage[0] = 0;
return FINISH;
}
if (state == STREAM_MAGIC_2) {
state = ACCEPT;
garbage[0] = 16;
return FINISH;
}
throw new StreamFormatException("ERR_EOF");
}
