private int deflate_fast(int flush)
{
// short hash_head = 0; // head of the hash chain
int hash_head = 0; // head of the hash chain
bool bflush; // set if current block must be flushed
while (true)
{
// Make sure that we always have enough lookahead, except
// at the End of the input file. We need MAX_MATCH bytes
// for the next match, plus MIN_MATCH bytes to insert the
// string following the next match.
if (lookahead < MIN_LOOKAHEAD)
{
fill_window();
if (lookahead < MIN_LOOKAHEAD && flush == (int)FlushStrategy.Z_NO_FLUSH)
{
return NeedMore;
}
if (lookahead == 0)
break; // internalFlush the current block
}
// Insert the string Window[strstart .. strstart+2] in the
// dictionary, and set hash_head to the head of the hash chain:
if (lookahead >= MIN_MATCH)
{
ins_h = (((ins_h) << hash_shift) ^ (window[(strstart) + (MIN_MATCH - 1)] & 0xff)) & hash_mask;
// prev[strstart&w_mask]=hash_head=head[ins_h];
hash_head = (head[ins_h] & 0xffff);
prev[strstart & w_mask] = head[ins_h];
head[ins_h] = (short)strstart;
}
// Find the longest match, discarding those <= prev_length.
// At this point we have always match_length < MIN_MATCH
if (hash_head != 0L && ((strstart - hash_head) & 0xffff) <= w_size - MIN_LOOKAHEAD)
{
// To simplify the code, we prevent matches with the string
// of Window index 0 (in particular we have to avoid a match
// of the string with itself at the start of the input file).
if (strategy != CompressionStrategy.Z_HUFFMAN_ONLY)
{
match_length = longest_match(hash_head);
}
// longest_match() sets match_start
}
if (match_length >= MIN_MATCH)
{
// check_match(strstart, match_start, match_length);
bflush = _tr_tally(strstart - match_start, match_length - MIN_MATCH);
lookahead -= match_length;
// Insert new strings in the hash table only if the match length
// is not too large. This saves time but degrades compression.
if (match_length <= max_lazy_match && lookahead >= MIN_MATCH)
{
match_length--; // string at strstart already in hash table
do
{
strstart++;
ins_h = ((ins_h << hash_shift) ^ (window[(strstart) + (MIN_MATCH - 1)] & 0xff)) & hash_mask;
// prev[strstart&w_mask]=hash_head=head[ins_h];
hash_head = (head[ins_h] & 0xffff);
prev[strstart & w_mask] = head[ins_h];
head[ins_h] = (short)strstart;
// strstart never exceeds WSIZE-MAX_MATCH, so there are
// always MIN_MATCH bytes ahead.
}
while (--match_length != 0);
strstart++;
}
else
{
strstart += match_length;
match_length = 0;
ins_h = window[strstart] & 0xff;
ins_h = (((ins_h) << hash_shift) ^ (window[strstart + 1] & 0xff)) & hash_mask;
// If lookahead < MIN_MATCH, ins_h is garbage, but it does not
// matter since it will be recomputed at next deflate call.
}
}
else
{
// No match, output a literal byte
bflush = _tr_tally(0, window[strstart] & 0xff);
lookahead--;
strstart++;
}
if (bflush)
{
flush_block_only(false);
if (strm.avail_out == 0)
return NeedMore;
}
}
flush_block_only(flush == (int)FlushStrategy.Z_FINISH);
if (strm.avail_out == 0)
{
if (flush == (int)FlushStrategy.Z_FINISH)
return FinishStarted;
else
return NeedMore;
}
return flush == (int)FlushStrategy.Z_FINISH ? FinishDone : BlockDone;
}