91 lines
3.8 KiB
C
91 lines
3.8 KiB
C
/*
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* Copyright (c) 2000 Silicon Graphics, Inc. All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of version 2 of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it would be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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*
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* Further, this software is distributed without any warranty that it is
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* free of the rightful claim of any third person regarding infringement
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* or the like. Any license provided herein, whether implied or
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* otherwise, applies only to this software file. Patent licenses, if
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* any, provided herein do not apply to combinations of this program with
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* other software, or any other product whatsoever.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write the Free Software Foundation, Inc., 59
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* Temple Place - Suite 330, Boston MA 02111-1307, USA.
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*
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* Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
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* Mountain View, CA 94043, or:
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*
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* http://www.sgi.com
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*
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* For further information regarding this notice, see:
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*
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* http://oss.sgi.com/projects/GenInfo/NoticeExplan/
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*/
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#ifndef _PATTERN_H_
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#define _PATTERN_H_
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/*
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* pattern_check(buf, buflen, pat, patlen, patshift)
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*
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* Check a buffer of length buflen against repeated occurrances of
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* a pattern whose length is patlen. Patshift can be used to rotate
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* the pattern by patshift bytes to the left.
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*
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* Patshift may be greater than patlen, the pattern will be rotated by
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* (patshift % patshift) bytes.
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*
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* pattern_check returns -1 if the buffer does not contain repeated
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* occurrances of the indicated pattern (shifted by patshift).
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*
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* The algorithm used to check the buffer relies on the fact that buf is
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* supposed to be repeated copies of pattern. The basic algorithm is
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* to validate the first patlen bytes of buf against the pat argument
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* passed in - then validate the next patlen bytes against the 1st patlen
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* bytes - the next (2*patlen) bytes against the 1st (2*pathen) bytes, and
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* so on. This algorithm only works when the assumption of a buffer full
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* of repeated copies of a pattern holds, and gives MUCH better results
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* then walking the buffer byte by byte.
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*
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* Performance wise, It appears to be about 5% slower than doing a straight
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* memcmp of 2 buffers, but the big win is that it does not require a
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* 2nd comparison buffer, only the pattern.
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*/
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int pattern_check( char * , int , char * , int , int );
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/*
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* pattern_fill(buf, buflen, pat, patlen, patshift)
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*
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* Fill a buffer of length buflen with repeated occurrances of
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* a pattern whose length is patlen. Patshift can be used to rotate
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* the pattern by patshift bytes to the left.
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*
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* Patshift may be greater than patlen, the pattern will be rotated by
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* (patshift % patlen) bytes.
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*
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* If buflen is not a multiple of patlen, a partial pattern will be written
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* in the last part of the buffer. This implies that a buffer which is
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* shorter than the pattern length will receive only a partial pattern ...
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*
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* pattern_fill always returns 0 - no validation of arguments is done.
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*
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* The algorithm used to fill the buffer relies on the fact that buf is
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* supposed to be repeated copies of pattern. The basic algorithm is
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* to fill the first patlen bytes of buf with the pat argument
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* passed in - then copy the next patlen bytes with the 1st patlen
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* bytes - the next (2*patlen) bytes with the 1st (2*pathen) bytes, and
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* so on. This algorithm only works when the assumption of a buffer full
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* of repeated copies of a pattern holds, and gives MUCH better results
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* then filling the buffer 1 byte at a time.
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*/
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int pattern_fill( char * , int , char * , int , int );
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#endif
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