Ionic.Zlib.DeflateManager.DeflateFast C# (CSharp) Method

        internal BlockState DeflateFast(FlushType 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)
                {
                    _fillWindow();
                    if (lookahead < MIN_LOOKAHEAD && flush == FlushType.None)
                    {
                        return BlockState.NeedMore;
                    }
                    if (lookahead == 0)
                        break; // flush 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] = unchecked((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 (compressionStrategy != CompressionStrategy.HuffmanOnly)
                    {
                        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 <= config.MaxLazy && 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] = unchecked((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 (_codec.AvailableBytesOut == 0)
                        return BlockState.NeedMore;
                }
            }

            flush_block_only(flush == FlushType.Finish);
            if (_codec.AvailableBytesOut == 0)
            {
                if (flush == FlushType.Finish)
                    return BlockState.FinishStarted;
                else
                    return BlockState.NeedMore;
            }
            return flush == FlushType.Finish ? BlockState.FinishDone : BlockState.BlockDone;
        }