| /* |
| * Copyright (c) 2000 Silicon Graphics, Inc. |
| * All Rights Reserved. |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License as |
| * published by the Free Software Foundation. |
| * |
| * This program is distributed in the hope that it would be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| #ifndef _PATTERN_H_ |
| #define _PATTERN_H_ |
| |
| /* |
| * pattern_check(buf, buflen, pat, patlen, patshift) |
| * |
| * Check a buffer of length buflen against repeated occurrances of |
| * a pattern whose length is patlen. Patshift can be used to rotate |
| * the pattern by patshift bytes to the left. |
| * |
| * Patshift may be greater than patlen, the pattern will be rotated by |
| * (patshift % patshift) bytes. |
| * |
| * pattern_check returns -1 if the buffer does not contain repeated |
| * occurrances of the indicated pattern (shifted by patshift). |
| * |
| * The algorithm used to check the buffer relies on the fact that buf is |
| * supposed to be repeated copies of pattern. The basic algorithm is |
| * to validate the first patlen bytes of buf against the pat argument |
| * passed in - then validate the next patlen bytes against the 1st patlen |
| * bytes - the next (2*patlen) bytes against the 1st (2*pathen) bytes, and |
| * so on. This algorithm only works when the assumption of a buffer full |
| * of repeated copies of a pattern holds, and gives MUCH better results |
| * then walking the buffer byte by byte. |
| * |
| * Performance wise, It appears to be about 5% slower than doing a straight |
| * memcmp of 2 buffers, but the big win is that it does not require a |
| * 2nd comparison buffer, only the pattern. |
| */ |
| int pattern_check( char * , int , char * , int , int ); |
| |
| /* |
| * pattern_fill(buf, buflen, pat, patlen, patshift) |
| * |
| * Fill a buffer of length buflen with repeated occurrances of |
| * a pattern whose length is patlen. Patshift can be used to rotate |
| * the pattern by patshift bytes to the left. |
| * |
| * Patshift may be greater than patlen, the pattern will be rotated by |
| * (patshift % patlen) bytes. |
| * |
| * If buflen is not a multiple of patlen, a partial pattern will be written |
| * in the last part of the buffer. This implies that a buffer which is |
| * shorter than the pattern length will receive only a partial pattern ... |
| * |
| * pattern_fill always returns 0 - no validation of arguments is done. |
| * |
| * The algorithm used to fill the buffer relies on the fact that buf is |
| * supposed to be repeated copies of pattern. The basic algorithm is |
| * to fill the first patlen bytes of buf with the pat argument |
| * passed in - then copy the next patlen bytes with the 1st patlen |
| * bytes - the next (2*patlen) bytes with the 1st (2*pathen) bytes, and |
| * so on. This algorithm only works when the assumption of a buffer full |
| * of repeated copies of a pattern holds, and gives MUCH better results |
| * then filling the buffer 1 byte at a time. |
| */ |
| int pattern_fill( char * , int , char * , int , int ); |
| |
| #endif |