112 lines
2.8 KiB
C
112 lines
2.8 KiB
C
/*
|
|
* This file is a part of Pcompress, a chunked parallel multi-
|
|
* algorithm lossless compression and decompression program.
|
|
*
|
|
* Copyright (C) 2012 Moinak Ghosh. All rights reserved.
|
|
* Use is subject to license terms.
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 3 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
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* moinakg@belenix.org, http://moinakg.wordpress.com/
|
|
*
|
|
* This RLE encoder is a simple approach to encode long runs of '0'
|
|
* bytes that typically are found in a bsdiff patch output. This
|
|
* does not encode repeating runs of other characters.
|
|
*/
|
|
|
|
#include <utils.h>
|
|
#include <stdio.h>
|
|
|
|
#define ZERO_MASK (32768)
|
|
#define DATA_MASK (32767)
|
|
#define COUNT_MAX (32767)
|
|
|
|
int
|
|
zero_rle_encode(const void *const ibuf, const unsigned int ilen,
|
|
void *obuf, unsigned int *const olen)
|
|
{
|
|
unsigned int pos1, pos2;
|
|
unsigned short count;
|
|
const uchar_t *const ib = ibuf;
|
|
uchar_t *ob = obuf;
|
|
|
|
pos2 = 0;
|
|
for (pos1=0; pos1<ilen && pos2<*olen;) {
|
|
count = 0;
|
|
if (ib[pos1] == 0) {
|
|
for (;pos1<ilen && ib[pos1]==0 && count<COUNT_MAX; pos1++) count++;
|
|
count |= ZERO_MASK;
|
|
*((unsigned short *)(ob + pos2)) = htons(count);
|
|
pos2 += 2;
|
|
} else {
|
|
unsigned int pos3, pos4, cnt, state;
|
|
pos3 = pos2;
|
|
pos2 += 2;
|
|
if (pos2 > *olen) break;
|
|
|
|
state = 0;
|
|
for (;pos1<ilen && pos2<*olen && count<COUNT_MAX;) {
|
|
if (ib[pos1] != 0) state = 0;
|
|
if (ib[pos1] == 0 && !state) {
|
|
cnt = 0;
|
|
pos4 = pos1;
|
|
state = 1;
|
|
// Lookahead if have ate least 4 consecutive zeroes
|
|
for (;pos4<ilen && ib[pos4] == 0; pos4++) cnt++;
|
|
if (cnt >= 4) break;
|
|
}
|
|
ob[pos2++] = ib[pos1++];
|
|
count++;
|
|
}
|
|
*((unsigned short *)(ob + pos3)) = htons(count);
|
|
}
|
|
}
|
|
*olen = pos2;
|
|
if (pos1 < ilen) {
|
|
return (-1);
|
|
} else {
|
|
return (0);
|
|
}
|
|
}
|
|
|
|
int
|
|
zero_rle_decode(const void* ibuf, unsigned int ilen,
|
|
void* obuf, unsigned int *olen)
|
|
{
|
|
unsigned int pos1, pos2, i;
|
|
unsigned short count;
|
|
const uchar_t *ib = ibuf;
|
|
uchar_t *ob = obuf;
|
|
|
|
pos2 = 0;
|
|
pos1 = 0;
|
|
for (; pos1<ilen && pos2<*olen;) {
|
|
count = ntohs(*((unsigned short *)(ib + pos1)));
|
|
pos1 += 2;
|
|
if (count & ZERO_MASK) {
|
|
count &= DATA_MASK;
|
|
for (i=0; i<count && pos2<*olen; i++)
|
|
ob[pos2++] = 0;
|
|
} else {
|
|
for (i=0; i<count && pos1<ilen && pos2<*olen; i++)
|
|
ob[pos2++] = ib[pos1++];
|
|
}
|
|
}
|
|
i = *olen;
|
|
*olen = pos2;
|
|
if (pos1 < ilen || pos2 < i) {
|
|
return (-1);
|
|
} else {
|
|
return (0);
|
|
}
|
|
}
|
|
|
|
|