/* deflate_rle.c -- compress data using RLE strategy of deflation algorithm

 *

 * Copyright (C) 1995-2024 Jean-loup Gailly and Mark Adler

 * For conditions of distribution and use, see copyright notice in zlib.h

 */

#include "zbuild.h"

#include "deflate.h"

#include "deflate_p.h"

#include "functable.h"

#include "compare256_rle.h"

#if OPTIMAL_CMP == 8

#  define compare256_rle compare256_rle_8

#else

#  define compare256_rle compare256_rle_64

#endif

/* ===========================================================================

 * 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.)

 */

Z_INTERNAL block_state deflate_rle(deflate_state *s, int flush) {

    unsigned char *window = s->window;

    unsigned char *scan;            /* scan goes up to strend for length of run */

    int bflush = 0;                 /* set if current block must be flushed */

    uint32_t match_len = 0;

    unsigned int lookahead = s->lookahead;

    unsigned int strstart = s->strstart;

    for (;;) {

        /* Make sure that we always have enough lookahead, except

         * at the end of the input file. We need STD_MAX_MATCH bytes

         * for the longest run, plus one for the unrolled loop.

         */

        if (UNLIKELY(lookahead <= STD_MAX_MATCH)) {

            s->lookahead = lookahead;

            s->strstart = strstart;

            PREFIX(fill_window)(s);

            lookahead = s->lookahead;

            strstart = s->strstart;

            if (UNLIKELY(lookahead <= STD_MAX_MATCH && flush == Z_NO_FLUSH))

                return need_more;

            if (UNLIKELY(lookahead == 0))

                break; /* flush the current block */

        }

        /* See how many times the previous byte repeats */

        if (LIKELY(lookahead >= STD_MIN_MATCH && strstart > 0)) {

            scan = window + strstart - 1;

            if (scan[0] == scan[1] && scan[1] == scan[2]) {

                match_len = compare256_rle(scan, scan+3)+2;

                match_len = MIN(match_len, lookahead);

            }

            Assert(scan+match_len <= window + s->window_size - 1, "wild scan");

        }

        /* Emit match if have run of STD_MIN_MATCH or longer, else emit literal */

        if (match_len >= STD_MIN_MATCH) {

            Assert(strstart <= UINT16_MAX, "strstart should fit in uint16_t");

            check_match(s, strstart, strstart - 1, match_len);

            bflush = zng_tr_tally_dist(s, 1, match_len - STD_MIN_MATCH);

            lookahead -= match_len;

            strstart += match_len;

            match_len = 0;

        } else {

            /* No match, output a literal byte */

            bflush = zng_tr_tally_lit(s, window[strstart]);

            lookahead--;

            strstart++;

        }

        if (bflush) {

            s->lookahead = lookahead;

            s->strstart = strstart;

            FLUSH_BLOCK(s, window, 0);

        }

    }

    s->lookahead = lookahead;

    s->strstart = strstart;

    s->insert = 0;

    if (flush == Z_FINISH) {

        FLUSH_BLOCK(s, window, 1);

        return finish_done;

    }

    if (s->sym_next)

        FLUSH_BLOCK(s, window, 0);

    return block_done;

}