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/*
* search.c
*
* 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; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will 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.
*/
#include <stdlib.h>
#include <string.h>
#include "kdumpid.h"
static void
compute_badchar(ssize_t *badchar, const unsigned char *s, ssize_t len)
{
size_t i = 1;
while (i < len)
badchar[*s++] = i++;
}
static void
compute_sfx(ssize_t *sfx, const unsigned char *s, ssize_t len)
{
ssize_t f, g, i;
sfx[len - 1] = len;
f = 0; /* bogus assignment to silence a warning */
g = len - 1;
for (i = len - 2; i >= 0; --i) {
if (i > g && sfx[i + len - 1 - f] < i - g)
sfx[i] = sfx[i + len - 1 - f];
else {
if (i < g)
g = i;
f = i;
while (g >= 0 && s[g] == s[g + len - 1 - f])
--g;
sfx[i] = f - g;
}
}
}
static void
compute_goodsfx(ssize_t *goodsfx, const unsigned char *s, ssize_t len)
{
ssize_t i, j, *sfx = goodsfx + len;
compute_sfx(sfx, s, len);
for (i = 0; i < len; ++i)
goodsfx[i] = len;
j = 0;
for (i = len - 1; i >= 0; --i)
if (sfx[i] == i + 1)
for (; j < len - 1 - i; ++j)
if (goodsfx[j] == len)
goodsfx[j] = len - 1 - i;
for (i = 0; i <= len - 2; ++i)
goodsfx[len - 1 - sfx[i]] = len - 1 - i;
}
/* A helper function for doing cpin forwards or backwards inside the
* find_bytestr() inner loop
*/
static inline void*
search_cpin(struct dump_desc *dd, void *buf, uint64_t addr, size_t len)
{
if (!dump_cpin(dd, buf, addr, len))
return buf;
else if (dd->flags & DIF_FORCE) {
memset(buf, 0, len);
return buf;
} else
return NULL;
}
/* Search for a constant byte string using the Boyer-Moore algorithm.
*/
static inline unsigned char*
search_buf(unsigned char *buf, size_t buflen,
const unsigned char *needle, size_t maxidx,
ssize_t *badchar, ssize_t *goodsfx)
{
if (!maxidx)
return memchr(buf, *needle, buflen);
while (buflen > maxidx) {
unsigned char *p;
ssize_t shift, i;
for (p = buf + maxidx, i = maxidx; i >= 0; --p, --i)
if (needle[i] != *p)
break;
if (i < 0)
return buf;
shift = i + 1 - badchar[*p];
if (shift < goodsfx[i])
shift = goodsfx[i];
buf += shift;
buflen -= shift;
}
return NULL;
}
/* Search for a constant byte string using the Boyer-Moore algorithm. */
uint64_t
dump_search_range(struct dump_desc *dd,
uint64_t start, uint64_t end,
const unsigned char *needle, size_t len)
{
void *dynalloc;
ssize_t *badchar, *goodsfx;
unsigned char *readbuf;
if (len > 1) {
dynalloc = calloc(sizeof(ssize_t) * (256 + 2*len)
+ 2*(len-1), 1);
if (!dynalloc)
return INVALID_ADDR;
badchar = dynalloc;
goodsfx = badchar + 256;
readbuf = dynalloc + sizeof(ssize_t) * (256 + 2*len);
compute_badchar(badchar, needle, len);
compute_goodsfx(goodsfx, needle, len);
} else {
dynalloc = NULL;
badchar = goodsfx = NULL;
readbuf = NULL;
}
--len; /* simplify offset computing */
while (start < end) {
off_t remain;
unsigned char *p, *q;
remain = dd->page_size - (start & (dd->page_size - 1));
if (remain > end - start)
remain = end - start;
if (remain > len) {
if (read_page(dd, start / dd->page_size)) {
if (! (dd->flags & DIF_FORCE))
break;
memset(dd->page, 0, dd->page_size);
}
p = dd->page + (start & (dd->page_size - 1));
} else {
remain += len;
p = search_cpin(dd, readbuf, start, remain);
if (!p)
break;
}
start += remain;
q = search_buf(p, remain, needle, len,
badchar, goodsfx);
if (q) {
if (dynalloc)
free(dynalloc);
return start + q - p - remain;
}
start -= len;
}
if (dynalloc)
free(dynalloc);
return INVALID_ADDR;
}
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