4 * This file is part of BeRTOS.
6 * Bertos is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
20 * As a special exception, you may use this file as part of a free software
21 * library without restriction. Specifically, if other files instantiate
22 * templates or use macros or inline functions from this file, or you compile
23 * this file and link it with other files to produce an executable, this
24 * file does not by itself cause the resulting executable to be covered by
25 * the GNU General Public License. This exception does not however
26 * invalidate any other reasons why the executable file might be covered by
27 * the GNU General Public License.
29 * Copyright 2004 Develer S.r.l. (http://www.develer.com/)
30 * Copyright 1999, 2000, 2001 Bernie Innocenti <bernie@codewiz.org>
34 * \brief General-purpose run-length {en,de}coding algorithm (implementation)
36 * Original source code from http://www.compuphase.com/compress.htm
38 * \author Bernie Innocenti <bernie@codewiz.org>
45 * Run-length encode \a len bytes from the \a input buffer
46 * to the \a output buffer.
48 int rle(unsigned char *output, const unsigned char *input, int len)
60 first = input[index++];
62 /* Scan for bytes identical to the first one */
63 while ((index < len) && (index - count < 127) && (input[index] == first))
66 if (index - count == 1)
68 /* Failed to "replicate" the current byte. See how many to copy.
70 while ((index < len) && (index - count < 127))
72 /* Avoid a replicate run of only 2-bytes after a literal run.
73 * There is no gain in this, and there is a risc of loss if the
74 * run after the two identical bytes is another literal run.
75 * So search for 3 identical bytes.
77 if ((input[index] == input[index - 1]) &&
78 ((index > 1) && (input[index] == input[index - 2])))
80 /* Reset the index so we can back up these three identical
81 * bytes in the next run.
90 /* Output a run of uncompressed bytes: write length and values */
91 *out++ = (unsigned char)(count - index);
92 for (i = count; i < index; i++)
97 /* Output a compressed run: write length and value */
98 *out++ = (unsigned char)(index - count);
105 /* Output EOF marker */
108 return (out - output);
113 * Run-length decode from the \a input buffer to the \a output
116 * \note The output buffer must be large enough to accomodate
117 * all decoded output.
119 int unrle(unsigned char *output, const unsigned char *input)
130 count = (signed char)*input++;
149 return (out - output);