lib/pattern.c

   1 /*
   2  * Copyright (c) 2000 Silicon Graphics, Inc.  All Rights Reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of version 2 of the GNU General Public License as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it would be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  11  *
  12  * Further, this software is distributed without any warranty that it is
  13  * free of the rightful claim of any third person regarding infringement
  14  * or the like.  Any license provided herein, whether implied or
  15  * otherwise, applies only to this software file.  Patent licenses, if
  16  * any, provided herein do not apply to combinations of this program with
  17  * other software, or any other product whatsoever.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write the Free Software Foundation, Inc., 59
  21  * Temple Place - Suite 330, Boston MA 02111-1307, USA.
  22  *
  23  * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
  24  * Mountain View, CA  94043, or:
  25  *
  26  * http://www.sgi.com
  27  *
  28  * For further information regarding this notice, see:
  29  *
  30  * http://oss.sgi.com/projects/GenInfo/NoticeExplan/
  31  */
  32 #include <string.h>
  33 #include "pattern.h"
  34
  35 /*
  36  * The routines in this module are used to fill/check a data buffer
  37  * with/against a known pattern.
  38  */
  39
  40 int
  41 pattern_check(buf, buflen, pat, patlen, patshift)
  42 char    *buf;
  43 int     buflen;
  44 char    *pat;
  45 int     patlen;
  46 int     patshift;
  47 {
  48     int         nb, ncmp, nleft;
  49     char        *cp;
  50
  51     if (patlen)
  52         patshift = patshift % patlen;
  53
  54     cp = buf;
  55     nleft = buflen;
  56
  57     /*
  58      * The following 2 blocks of code are to compare the first patlen
  59      * bytes of buf.  We need 2 checks if patshift is > 0 since we
  60      * must check the last (patlen - patshift) bytes, and then the
  61      * first (patshift) bytes.
  62      */
  63
  64     nb = patlen - patshift;
  65     if (nleft < nb) {
  66         return (memcmp(cp, pat + patshift, nleft) ? -1 : 0);
  67     } else {
  68         if (memcmp(cp, pat + patshift, nb))
  69             return -1;
  70
  71         nleft -= nb;
  72         cp += nb;
  73     }
  74
  75     if (patshift > 0) {
  76         nb = patshift;
  77         if (nleft < nb) {
  78             return (memcmp(cp, pat, nleft) ? -1 : 0);
  79         } else {
  80             if (memcmp(cp, pat, nb))
  81                 return -1;
  82
  83             nleft -= nb;
  84             cp += nb;
  85         }
  86     }
  87
  88     /*
  89      * Now, verify the rest of the buffer using the algorithm described
  90      * in the function header.
  91      */
  92
  93     ncmp = cp - buf;
  94     while (ncmp < buflen) {
  95         nb = (ncmp < nleft) ? ncmp : nleft;
  96         if (memcmp(buf, cp, nb))
  97             return -1;
  98
  99         cp += nb;
 100         ncmp += nb;
 101         nleft -= nb;
 102     }
 103
 104     return 0;
 105 }
 106
 107 int
 108 pattern_fill(buf, buflen, pat, patlen, patshift)
 109 char    *buf;
 110 int     buflen;
 111 char    *pat;
 112 int     patlen;
 113 int     patshift;
 114 {
 115     int         trans, ncopied, nleft;
 116     char        *cp;
 117
 118     if (patlen)
 119         patshift = patshift % patlen;
 120
 121     cp = buf;
 122     nleft = buflen;
 123
 124     /*
 125      * The following 2 blocks of code are to fill the first patlen
 126      * bytes of buf.  We need 2 sections if patshift is > 0 since we
 127      * must first copy the last (patlen - patshift) bytes into buf[0]...,
 128      * and then the first (patshift) bytes of pattern following them.
 129      */
 130
 131     trans = patlen - patshift;
 132     if (nleft < trans) {
 133         memcpy(cp, pat + patshift, nleft);
 134         return 0;
 135     } else {
 136         memcpy(cp, pat + patshift, trans);
 137         nleft -= trans;
 138         cp += trans;
 139     }
 140
 141     if (patshift > 0) {
 142         trans = patshift;
 143         if (nleft < trans) {
 144             memcpy(cp, pat, nleft);
 145             return 0;
 146         } else {
 147             memcpy(cp, pat, trans);
 148             nleft -= trans;
 149             cp += trans;
 150         }
 151     }
 152
 153     /*
 154      * Now, fill the rest of the buffer using the algorithm described
 155      * in the function header comment.
 156      */
 157
 158     ncopied = cp - buf;
 159     while (ncopied < buflen) {
 160         trans = (ncopied < nleft) ? ncopied : nleft;
 161         memcpy(cp, buf, trans);
 162         cp += trans;
 163         ncopied += trans;
 164         nleft -= trans;
 165     }
 166
 167     return(0);
 168 }