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/* 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
#elif defined(HAVE_BUILTIN_CTZLL)
# define compare256_rle compare256_rle_64
#elif defined(HAVE_BUILTIN_CTZ)
# define compare256_rle compare256_rle_32
#else
# define compare256_rle compare256_rle_16
#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) {
int bflush = 0; /* set if current block must be flushed */
unsigned char *scan; /* scan goes up to strend for length of run */
uint32_t match_len = 0;
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 (s->lookahead <= STD_MAX_MATCH) {
PREFIX(fill_window)(s);
if (s->lookahead <= STD_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 */
if (s->lookahead >= STD_MIN_MATCH && s->strstart > 0) {
scan = s->window + s->strstart - 1;
if (scan[0] == scan[1] && scan[1] == scan[2]) {
match_len = compare256_rle(scan, scan+3)+2;
match_len = MIN(match_len, s->lookahead);
match_len = MIN(match_len, STD_MAX_MATCH);
}
Assert(scan+match_len <= s->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(s->strstart <= UINT16_MAX, "strstart should fit in uint16_t");
check_match(s, (Pos)s->strstart, (Pos)(s->strstart - 1), match_len);
bflush = zng_tr_tally_dist(s, 1, match_len - STD_MIN_MATCH);
s->lookahead -= match_len;
s->strstart += match_len;
match_len = 0;
} else {
/* No match, output a literal byte */
bflush = zng_tr_tally_lit(s, s->window[s->strstart]);
s->lookahead--;
s->strstart++;
}
if (bflush)
FLUSH_BLOCK(s, 0);
}
s->insert = 0;
if (flush == Z_FINISH) {
FLUSH_BLOCK(s, 1);
return finish_done;
}
if (s->sym_next)
FLUSH_BLOCK(s, 0);
return block_done;
}
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