mirror of https://github.com/opencv/opencv.git
Open Source Computer Vision Library
https://opencv.org/
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
85 lines
3.0 KiB
85 lines
3.0 KiB
/* 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 "compare256_rle.h" |
|
#include "deflate.h" |
|
#include "deflate_p.h" |
|
#include "functable.h" |
|
|
|
#ifdef UNALIGNED_OK |
|
# if defined(UNALIGNED64_OK) && defined(HAVE_BUILTIN_CTZLL) |
|
# define compare256_rle compare256_rle_unaligned_64 |
|
# elif defined(HAVE_BUILTIN_CTZ) |
|
# define compare256_rle compare256_rle_unaligned_32 |
|
# else |
|
# define compare256_rle compare256_rle_unaligned_16 |
|
# endif |
|
#else |
|
# define compare256_rle compare256_rle_c |
|
#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) { |
|
check_match(s, s->strstart, 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; |
|
}
|
|
|