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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2000 Silicon Graphics, Inc.
* All Rights Reserved.
*/
#include <string.h>
#include "pattern.h"
/*
* The routines in this module are used to fill/check a data buffer
* with/against a known pattern.
*/
int
pattern_check(buf, buflen, pat, patlen, patshift)
char *buf;
int buflen;
char *pat;
int patlen;
int patshift;
{
int nb, ncmp, nleft;
char *cp;
if (patlen)
patshift = patshift % patlen;
cp = buf;
nleft = buflen;
/*
* The following 2 blocks of code are to compare the first patlen
* bytes of buf. We need 2 checks if patshift is > 0 since we
* must check the last (patlen - patshift) bytes, and then the
* first (patshift) bytes.
*/
nb = patlen - patshift;
if (nleft < nb) {
return (memcmp(cp, pat + patshift, nleft) ? -1 : 0);
} else {
if (memcmp(cp, pat + patshift, nb))
return -1;
nleft -= nb;
cp += nb;
}
if (patshift > 0) {
nb = patshift;
if (nleft < nb) {
return (memcmp(cp, pat, nleft) ? -1 : 0);
} else {
if (memcmp(cp, pat, nb))
return -1;
nleft -= nb;
cp += nb;
}
}
/*
* Now, verify the rest of the buffer using the algorithm described
* in the function header.
*/
ncmp = cp - buf;
while (ncmp < buflen) {
nb = (ncmp < nleft) ? ncmp : nleft;
if (memcmp(buf, cp, nb))
return -1;
cp += nb;
ncmp += nb;
nleft -= nb;
}
return 0;
}
int
pattern_fill(buf, buflen, pat, patlen, patshift)
char *buf;
int buflen;
char *pat;
int patlen;
int patshift;
{
int trans, ncopied, nleft;
char *cp;
if (patlen)
patshift = patshift % patlen;
cp = buf;
nleft = buflen;
/*
* The following 2 blocks of code are to fill the first patlen
* bytes of buf. We need 2 sections if patshift is > 0 since we
* must first copy the last (patlen - patshift) bytes into buf[0]...,
* and then the first (patshift) bytes of pattern following them.
*/
trans = patlen - patshift;
if (nleft < trans) {
memcpy(cp, pat + patshift, nleft);
return 0;
} else {
memcpy(cp, pat + patshift, trans);
nleft -= trans;
cp += trans;
}
if (patshift > 0) {
trans = patshift;
if (nleft < trans) {
memcpy(cp, pat, nleft);
return 0;
} else {
memcpy(cp, pat, trans);
nleft -= trans;
cp += trans;
}
}
/*
* Now, fill the rest of the buffer using the algorithm described
* in the function header comment.
*/
ncopied = cp - buf;
while (ncopied < buflen) {
trans = (ncopied < nleft) ? ncopied : nleft;
memcpy(cp, buf, trans);
cp += trans;
ncopied += trans;
nleft -= trans;
}
return(0);
}
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