pcompress/filters/analyzer/analyzer.c

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/*
* This file is a part of Pcompress, a chunked parallel multi-
* algorithm lossless compression and decompression program.
*
* Copyright (C) 2012-2014 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.
*
* 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/
*/
#include "utils.h"
#include "analyzer.h"
#define FIFTY_PCT(x) (((x)/10) * 5)
#define FORTY_PCT(x) (((x)/10) * 4)
#define ONE_PCT(x) ((x)/100)
void
analyze_buffer(void *src, uint64_t srclen, analyzer_ctx_t *actx)
{
uchar_t *src1 = (uchar_t *)src;
uint64_t i, tot8b, tot_8b, lbytes;
uchar_t cur_byte, prev_byte;
uint64_t tag1, tag2, tag3;
double tagcnt, pct_tag;
int markup;
/*
* Count number of 8-bit binary bytes and XML tags in source.
*/
tot8b = 0;
tag1 = 0;
tag2 = 0;
tag3 = 0;
lbytes = 0;
prev_byte = cur_byte = 0;
for (i = 0; i < srclen; i++) {
cur_byte = src1[i];
tot8b += (cur_byte & 0x80); // This way for possible auto-vectorization
lbytes += (cur_byte < 32);
tag1 += (cur_byte == '<');
tag2 += (cur_byte == '>');
tag3 += ((prev_byte == '<') & (cur_byte == '/'));
tag3 += ((prev_byte == '/') & (cur_byte == '>'));
if (cur_byte != ' ')
prev_byte = cur_byte;
}
/*
* Heuristics for detecting BINARY vs generic TEXT vs XML data at various
* significance levels.
*/
tot_8b = tot8b / 0x80 + lbytes;
tagcnt = tag1 + tag2 + tag3;
pct_tag = tagcnt / (double)srclen;
if (tot_8b > FORTY_PCT(srclen)) {
actx->forty_pct.btype = TYPE_BINARY;
} else {
actx->forty_pct.btype = TYPE_TEXT;
}
if (tot_8b > FIFTY_PCT(srclen)) {
actx->fifty_pct.btype = TYPE_BINARY;
} else {
actx->fifty_pct.btype = TYPE_TEXT;
}
tot8b /= 0x80;
if (tot8b == 0 && lbytes < ((srclen>>1) + (srclen>>2) + (srclen>>3))) {
actx->one_pct.btype = TYPE_TEXT;
}
markup = 0;
if (tag1 > tag2 - 4 && tag1 < tag2 + 4 && tag3 > (double)tag1 * 0.40 &&
tagcnt > (double)srclen * 0.001)
markup = 1;
if (markup) {
if (actx->forty_pct.btype == TYPE_TEXT)
actx->forty_pct.btype |= TYPE_MARKUP;
if (actx->fifty_pct.btype == TYPE_TEXT)
actx->fifty_pct.btype |= TYPE_MARKUP;
if (actx->one_pct.btype == TYPE_TEXT)
actx->one_pct.btype |= TYPE_MARKUP;
}
}
int
analyze_buffer_simple(void *src, uint64_t srclen)
{
uchar_t *src1 = (uchar_t *)src;
uint64_t i, tot8b, lbytes;
uchar_t cur_byte;
int btype = TYPE_UNKNOWN;
/*
* Count number of 8-bit binary bytes in source
*/
tot8b = 0;
lbytes = 0;
for (i = 0; i < srclen; i++) {
cur_byte = src1[i];
tot8b += (cur_byte & 0x80); // This way for possible auto-vectorization
lbytes += (cur_byte < 32);
}
/*
* Heuristics for detecting BINARY vs generic TEXT
*/
tot8b /= 0x80;
if (tot8b == 0 && lbytes < ((srclen>>1) + (srclen>>2) + (srclen>>3))) {
btype = TYPE_TEXT;
}
return (btype);
}