vendor: OpenCV 5.0.0 snapshot at 40738fb16ceddb5fb3fea747585f7ce6abb0605b

2026-08-22 00:10:33 +08:00
commit f7f077da11
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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 "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;
+}