pcompress/filters/analyzer/analyzer.c

/*
 * 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"

int
analyze_buffer(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);
}