151 lines
3.8 KiB
C
151 lines
3.8 KiB
C
/**
|
|
* \file
|
|
* <!--
|
|
* This file is part of BeRTOS.
|
|
*
|
|
* Bertos is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*
|
|
* As a special exception, you may use this file as part of a free software
|
|
* library without restriction. Specifically, if other files instantiate
|
|
* templates or use macros or inline functions from this file, or you compile
|
|
* this file and link it with other files to produce an executable, this
|
|
* file does not by itself cause the resulting executable to be covered by
|
|
* the GNU General Public License. This exception does not however
|
|
* invalidate any other reasons why the executable file might be covered by
|
|
* the GNU General Public License.
|
|
*
|
|
* Copyright 2004 Develer S.r.l. (http://www.develer.com/)
|
|
* Copyright 1999, 2000, 2001 Bernie Innocenti <bernie@codewiz.org>
|
|
*
|
|
* -->
|
|
*
|
|
* \brief General-purpose run-length {en,de}coding algorithm (implementation)
|
|
*
|
|
* Original source code from http://www.compuphase.com/compress.htm
|
|
*
|
|
* \author Bernie Innocenti <bernie@codewiz.org>
|
|
*/
|
|
|
|
#include "rle.h"
|
|
|
|
|
|
/**
|
|
* Run-length encode \a len bytes from the \a input buffer
|
|
* to the \a output buffer.
|
|
*/
|
|
int rle(unsigned char *output, const unsigned char *input, int len)
|
|
{
|
|
int count, index, i;
|
|
unsigned char first;
|
|
unsigned char *out;
|
|
|
|
|
|
out = output;
|
|
count = 0;
|
|
while (count < len)
|
|
{
|
|
index = count;
|
|
first = input[index++];
|
|
|
|
/* Scan for bytes identical to the first one */
|
|
while ((index < len) && (index - count < 127) && (input[index] == first))
|
|
index++;
|
|
|
|
if (index - count == 1)
|
|
{
|
|
/* Failed to "replicate" the current byte. See how many to copy.
|
|
*/
|
|
while ((index < len) && (index - count < 127))
|
|
{
|
|
/* Avoid a replicate run of only 2-bytes after a literal run.
|
|
* There is no gain in this, and there is a risc of loss if the
|
|
* run after the two identical bytes is another literal run.
|
|
* So search for 3 identical bytes.
|
|
*/
|
|
if ((input[index] == input[index - 1]) &&
|
|
((index > 1) && (input[index] == input[index - 2])))
|
|
{
|
|
/* Reset the index so we can back up these three identical
|
|
* bytes in the next run.
|
|
*/
|
|
index -= 2;
|
|
break;
|
|
}
|
|
|
|
index++;
|
|
}
|
|
|
|
/* Output a run of uncompressed bytes: write length and values */
|
|
*out++ = (unsigned char)(count - index);
|
|
for (i = count; i < index; i++)
|
|
*out++ = input[i];
|
|
}
|
|
else
|
|
{
|
|
/* Output a compressed run: write length and value */
|
|
*out++ = (unsigned char)(index - count);
|
|
*out++ = first;
|
|
}
|
|
|
|
count = index;
|
|
}
|
|
|
|
/* Output EOF marker */
|
|
*out++ = 0;
|
|
|
|
return (out - output);
|
|
}
|
|
|
|
|
|
/**
|
|
* Run-length decode from the \a input buffer to the \a output
|
|
* buffer.
|
|
*
|
|
* \note The output buffer must be large enough to accomodate
|
|
* all decoded output.
|
|
*/
|
|
int unrle(unsigned char *output, const unsigned char *input)
|
|
{
|
|
signed char count;
|
|
unsigned char *out;
|
|
unsigned char value;
|
|
|
|
|
|
out = output;
|
|
|
|
for (;;)
|
|
{
|
|
count = (signed char)*input++;
|
|
if (count > 0)
|
|
{
|
|
/* replicate run */
|
|
value = *input++;
|
|
while (count--)
|
|
*out++ = value;
|
|
}
|
|
else if (count < 0)
|
|
{
|
|
/* literal run */
|
|
while (count++)
|
|
*out++ = *input++;
|
|
}
|
|
else
|
|
/* EOF */
|
|
break;
|
|
}
|
|
|
|
return (out - output);
|
|
}
|