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86 lines
3.0 KiB
86 lines
3.0 KiB
11 months ago
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/* deflate_rle.c -- compress data using RLE strategy of deflation algorithm
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*
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* Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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#include "zbuild.h"
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#include "compare256_rle.h"
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#include "deflate.h"
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#include "deflate_p.h"
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#include "functable.h"
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#ifdef UNALIGNED_OK
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# if defined(UNALIGNED64_OK) && defined(HAVE_BUILTIN_CTZLL)
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# define compare256_rle compare256_rle_unaligned_64
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# elif defined(HAVE_BUILTIN_CTZ)
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# define compare256_rle compare256_rle_unaligned_32
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# else
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# define compare256_rle compare256_rle_unaligned_16
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# endif
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#else
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# define compare256_rle compare256_rle_c
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#endif
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/* ===========================================================================
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* For Z_RLE, simply look for runs of bytes, generate matches only of distance
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* one. Do not maintain a hash table. (It will be regenerated if this run of
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* deflate switches away from Z_RLE.)
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*/
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Z_INTERNAL block_state deflate_rle(deflate_state *s, int flush) {
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int bflush = 0; /* set if current block must be flushed */
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unsigned char *scan; /* scan goes up to strend for length of run */
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uint32_t match_len = 0;
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for (;;) {
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/* Make sure that we always have enough lookahead, except
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* at the end of the input file. We need STD_MAX_MATCH bytes
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* for the longest run, plus one for the unrolled loop.
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*/
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if (s->lookahead <= STD_MAX_MATCH) {
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PREFIX(fill_window)(s);
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if (s->lookahead <= STD_MAX_MATCH && flush == Z_NO_FLUSH)
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return need_more;
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if (s->lookahead == 0)
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break; /* flush the current block */
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}
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/* See how many times the previous byte repeats */
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if (s->lookahead >= STD_MIN_MATCH && s->strstart > 0) {
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scan = s->window + s->strstart - 1;
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if (scan[0] == scan[1] && scan[1] == scan[2]) {
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match_len = compare256_rle(scan, scan+3)+2;
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match_len = MIN(match_len, s->lookahead);
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match_len = MIN(match_len, STD_MAX_MATCH);
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}
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Assert(scan+match_len <= s->window + s->window_size - 1, "wild scan");
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}
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/* Emit match if have run of STD_MIN_MATCH or longer, else emit literal */
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if (match_len >= STD_MIN_MATCH) {
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check_match(s, s->strstart, s->strstart - 1, match_len);
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bflush = zng_tr_tally_dist(s, 1, match_len - STD_MIN_MATCH);
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s->lookahead -= match_len;
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s->strstart += match_len;
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match_len = 0;
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} else {
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/* No match, output a literal byte */
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bflush = zng_tr_tally_lit(s, s->window[s->strstart]);
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s->lookahead--;
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s->strstart++;
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}
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if (bflush)
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FLUSH_BLOCK(s, 0);
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}
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s->insert = 0;
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if (flush == Z_FINISH) {
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FLUSH_BLOCK(s, 1);
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return finish_done;
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}
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if (s->sym_next)
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FLUSH_BLOCK(s, 0);
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return block_done;
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}
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