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85 lines
3.0 KiB
85 lines
3.0 KiB
/* 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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