70 lines
2.1 KiB
C
70 lines
2.1 KiB
C
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/*
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* This file is a part of Pcompress, a chunked parallel multi-
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* algorithm lossless compression and decompression program.
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*
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* Copyright (C) 2012-2014 Moinak Ghosh. All rights reserved.
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* Use is subject to license terms.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 3 of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program.
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* If not, see <http://www.gnu.org/licenses/>.
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*
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* moinakg@belenix.org, http://moinakg.wordpress.com/
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*/
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#include "utils.h"
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int
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analyze_buffer(void *src, uint64_t srclen, int btype, int adapt_mode)
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{
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uchar_t *src1 = (uchar_t *)src;
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int stype = PC_SUBTYPE(btype);
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if (btype == TYPE_UNKNOWN || stype == TYPE_ARCHIVE_TAR) {
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uint32_t freq[256], freq0x80[2] = {0};
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uint64_t i, alphabetNum = 0, tot8b = 0;
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uchar_t cur_byte;
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/*
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* Count number of 8-bit binary bytes and XML tags in source.
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*/
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tot8b = 0;
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for (i = 0; i < srclen; i++) {
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cur_byte = src1[i];
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tot8b += (cur_byte & 0x80); // This way for possible auto-vectorization
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freq[cur_byte]++;
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}
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for (i = 0; i < 256; i++)
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freq0x80[i>>7]+=freq[i];
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for(i = 'a'; i <= 'z'; i++)
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alphabetNum+=freq[i];
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/*
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* Heuristics for detecting BINARY vs generic TEXT
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*/
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tot8b /= 0x80;
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if (tot8b < (srclen>>2 + srclen>>3)) {
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btype = TYPE_TEXT;
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if (freq0x80[1]<(srclen>>3) && (freq[' ']>(srclen>>7))
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&& (freq['a']+freq['e']+freq['t']>(srclen>>4))
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&& alphabetNum>(srclen>>2)) {
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btype |= TYPE_ENGLISH;
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}
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}
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}
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return (btype);
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}
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