/** * \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); }