Function deflate_rle

zlib/deflate.c:1683–1735

=========================================================================== * For Z_RLE, simply look for runs of bytes, generate matches only of distance * one. Do not maintain a hash table. (It will be regenerated if this run of * deflate switches away from Z_RLE.) */

(s, flush)

 * deflate switches away from Z_RLE.)
 */
local block_state deflate_rle(s, flush)
    deflate_state *s;
    int flush;
{
    int bflush;         /* set if current block must be flushed */
    uInt run;           /* length of run */
    uInt max;           /* maximum length of run */
    uInt prev;          /* byte at distance one to match */
    Bytef *scan;        /* scan for end of run */

    for (;;) {
        /* Make sure that we always have enough lookahead, except
         * at the end of the input file. We need MAX_MATCH bytes
         * for the longest encodable run.
         */
        if (s->lookahead < MAX_MATCH) {
            fill_window(s);
            if (s->lookahead < MAX_MATCH && flush == Z_NO_FLUSH) {
                return need_more;
            }
            if (s->lookahead == 0) break; /* flush the current block */
        }

        /* See how many times the previous byte repeats */
        run = 0;
        if (s->strstart > 0) {      /* if there is a previous byte, that is */
            max = s->lookahead < MAX_MATCH ? s->lookahead : MAX_MATCH;
            scan = s->window + s->strstart - 1;
            prev = *scan++;
            do {
                if (*scan++ != prev)
                    break;
            } while (++run < max);
        }

        /* Emit match if have run of MIN_MATCH or longer, else emit literal */
        if (run >= MIN_MATCH) {
            check_match(s, s->strstart, s->strstart - 1, run);
            _tr_tally_dist(s, 1, run - MIN_MATCH, bflush);
            s->lookahead -= run;
            s->strstart += run;
        } else {
            /* No match, output a literal byte */
            Tracevv((stderr,"%c", s->window[s->strstart]));
            _tr_tally_lit (s, s->window[s->strstart], bflush);
            s->lookahead--;
            s->strstart++;
        }
        if (bflush) FLUSH_BLOCK(s, 0);
    }
    FLUSH_BLOCK(s, flush == Z_FINISH);
    return flush == Z_FINISH ? finish_done : block_done;
}
#endif