System.util.zlib.Deflate.longest_match C# (CSharp) Method

        internal int longest_match(int cur_match){
            int chain_length = max_chain_length; // max hash chain length
            int scan = strstart;                 // current string
            int match;                           // matched string
            int len;                             // length of current match
            int best_len = prev_length;          // best match length so far
            int limit = strstart>(w_size-MIN_LOOKAHEAD) ?
                strstart-(w_size-MIN_LOOKAHEAD) : 0;
            int nice_match=this.nice_match;

            // Stop when cur_match becomes <= limit. To simplify the code,
            // we prevent matches with the string of window index 0.

            int wmask = w_mask;

            int strend = strstart + MAX_MATCH;
            byte scan_end1 = window[scan+best_len-1];
            byte scan_end = window[scan+best_len];

            // The code is optimized for HASH_BITS >= 8 and MAX_MATCH-2 multiple of 16.
            // It is easy to get rid of this optimization if necessary.

            // Do not waste too much time if we already have a good match:
            if (prev_length >= good_match) {
                chain_length >>= 2;
            }

            // Do not look for matches beyond the end of the input. This is necessary
            // to make deflate deterministic.
            if (nice_match > lookahead) nice_match = lookahead;

            do {
                match = cur_match;

                // Skip to next match if the match length cannot increase
                // or if the match length is less than 2:
                if (window[match+best_len]   != scan_end  ||
                    window[match+best_len-1] != scan_end1 ||
                    window[match]       != window[scan]     ||
                    window[++match]     != window[scan+1])      continue;

                // The check at best_len-1 can be removed because it will be made
                // again later. (This heuristic is not always a win.)
                // It is not necessary to compare scan[2] and match[2] since they
                // are always equal when the other bytes match, given that
                // the hash keys are equal and that HASH_BITS >= 8.
                scan += 2; match++;

                // We check for insufficient lookahead only every 8th comparison;
                // the 256th check will be made at strstart+258.
                do {
                } while (window[++scan] == window[++match] &&
                    window[++scan] == window[++match] &&
                    window[++scan] == window[++match] &&
                    window[++scan] == window[++match] &&
                    window[++scan] == window[++match] &&
                    window[++scan] == window[++match] &&
                    window[++scan] == window[++match] &&
                    window[++scan] == window[++match] &&
                    scan < strend);

                len = MAX_MATCH - (int)(strend - scan);
                scan = strend - MAX_MATCH;

                if(len>best_len) {
                    match_start = cur_match;
                    best_len = len;
                    if (len >= nice_match) break;
                    scan_end1  = window[scan+best_len-1];
                    scan_end   = window[scan+best_len];
                }

            } while ((cur_match = (prev[cur_match & wmask]&0xffff)) > limit
                && --chain_length != 0);

            if (best_len <= lookahead) return best_len;
            return lookahead;
        }