pcompress/bsdiff/rle_encoder.c

141 lines
3.6 KiB
C
Raw Permalink Normal View History

/*
* This file is a part of Pcompress, a chunked parallel multi-
* algorithm lossless compression and decompression program.
*
2013-03-07 14:56:48 +00:00
* Copyright (C) 2012-2013 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.
*
2013-03-07 14:56:48 +00:00
* You should have received a copy of the GNU Lesser General Public
* License along with this program.
* If not, see <http://www.gnu.org/licenses/>.
*
* 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>
#include <string.h>
#define ZERO_MASK (32768)
#define DATA_MASK (32767)
#define COUNT_MAX (32767)
int
zero_rle_encode(const void *ibuf, const unsigned int ilen,
void *obuf, unsigned int *olen)
{
unsigned int pos1, pos2, sz;
unsigned short count;
const uchar_t *ib = (const uchar_t *)ibuf;
uchar_t *ob = (uchar_t *)obuf;
uint64_t val;
sz = sizeof (val) - 1;
pos2 = 0;
for (pos1=0; pos1<ilen && pos2<*olen;) {
count = 0;
if (ib[pos1] == 0) {
/*
* We have a run of zeroes. Count them and store only the count.
*/
while (pos1 < (ilen - sz) && count < (COUNT_MAX - sz)) {
val = U64_P(ib+pos1);
if (val) break;
pos1 += sizeof (val); count += sizeof (val);
}
for (;pos1<ilen && ib[pos1]==0 && count<COUNT_MAX; pos1++) ++count;
count |= ZERO_MASK;
U16_P(ob + pos2) = htons(count);
pos2 += 2;
if (pos2 > *olen) break;
} else {
unsigned int pos3, pos4, 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) {
state = 1;
// Lookahead if there are at least 4 consecutive zeroes
if (ilen > 3) {
pos4 = *((unsigned int *)(ib+pos1));
if (!pos4) break;
}
}
ob[pos2++] = ib[pos1++];
++count;
}
U16_P(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 = (const uchar_t *)ibuf;
uchar_t *ob = (uchar_t *)obuf;
pos2 = 0;
pos1 = 0;
for (; pos1<ilen && pos2<*olen;) {
count = ntohs(U16_P(ib + pos1));
pos1 += 2;
if (count & ZERO_MASK) {
count &= DATA_MASK;
if (pos2 + count > *olen) {
log_msg(LOG_ERR, 0, "Output buffer overflow in Zero RLE decode.\n");
return (-1);
}
memset(ob+pos2, 0, count);
pos2 += count;
} else {
if (pos1 + count > ilen) {
log_msg(LOG_ERR, 0, "Input underflow in Zero RLE decode.\n");
return (-1);
}
if (pos2 + count > *olen) {
log_msg(LOG_ERR, 0, "Output buffer overflow in Zero RLE decode.\n");
return (-1);
}
memcpy(ob+pos2, ib+pos1, count);
pos2 += count;
pos1 += count;
}
}
i = *olen;
*olen = pos2;
if (pos1 < ilen || pos2 < i) {
return (-1);
} else {
return (0);
}
}