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/*
* Copyright (c) 2012 Damien Miller <djm@mindrot.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* $Id: modpipe.c,v 1.1 2012/12/11 23:54:40 djm Exp $ */
#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <err.h>
#include <errno.h>
static void
usage(void)
{
fprintf(stderr, "Usage: modpipe [-m modspec ...] < in > out\n");
fprintf(stderr, "modspec is one of:\n");
fprintf(stderr, " xor:offset:value - XOR \"value\" at \"offset\"\n");
fprintf(stderr, " andor:offset:val1:val2 - AND \"val1\" then OR \"val2\" at \"offset\"\n");
exit(1);
}
#define MAX_MODIFICATIONS 256
struct modification {
enum { MOD_XOR, MOD_AND_OR } what;
u_int64_t offset;
u_int8_t m1, m2;
};
static void
parse_modification(const char *s, struct modification *m)
{
char what[16+1];
int n;
bzero(m, sizeof(*m));
if ((n = sscanf(s, "%16[^:]%*[:]%lli%*[:]%hhi%*[:]%hhi",
what, &m->offset, &m->m1, &m->m2)) < 3)
errx(1, "Invalid modification spec \"%s\"", s);
if (strcasecmp(what, "xor") == 0) {
m->what = MOD_XOR;
if (n > 3)
errx(1, "Invalid modification spec \"%s\"", s);
} else if (strcasecmp(what, "andor") == 0) {
m->what = MOD_AND_OR;
if (n != 4)
errx(1, "Invalid modification spec \"%s\"", s);
} else
errx(1, "Invalid modification type \"%s\"", what);
}
int
main(int argc, char **argv)
{
int ch;
u_char buf[8192];
size_t total;
ssize_t r, s, o;
struct modification mods[MAX_MODIFICATIONS];
u_int i, num_mods = 0;
while ((ch = getopt(argc, argv, "m:")) != -1) {
switch (ch) {
case 'm':
if (num_mods >= MAX_MODIFICATIONS)
errx(1, "Too many modifications");
parse_modification(optarg, &(mods[num_mods++]));
break;
default:
usage();
/* NOTREACHED */
}
}
for (total = 0;;) {
r = s = read(STDIN_FILENO, buf, sizeof(buf));
if (r == 0)
return 0;
if (r < 0) {
if (errno == EAGAIN || errno == EINTR)
continue;
err(1, "read");
}
for (i = 0; i < num_mods; i++) {
if (mods[i].offset < total ||
mods[i].offset >= total + s)
continue;
switch (mods[i].what) {
case MOD_XOR:
buf[mods[i].offset - total] ^= mods[i].m1;
break;
case MOD_AND_OR:
buf[mods[i].offset - total] &= mods[i].m1;
buf[mods[i].offset - total] |= mods[i].m2;
break;
}
}
for (o = 0; o < s; o += r) {
r = write(STDOUT_FILENO, buf, s - o);
if (r == 0)
return 0;
if (r < 0) {
if (errno == EAGAIN || errno == EINTR)
continue;
err(1, "write");
}
}
total += s;
}
return 0;
}
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