39 lines
782 B
C
39 lines
782 B
C
/*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License,
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* version 2 as published by the Free Software Foundation.
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*
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* (C) John Crispin <blogic@openwrt.org>
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*/
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <errno.h>
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int main(int argc, char **argv)
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{
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uint32_t t = 0, sum = 0x55aa55aa;
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int fd;
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if ((argc != 2) || ((fd = open(argv[1], O_RDWR)) == -1)) {
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fprintf(stderr, "Usage: %s input_file\n", *argv);
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return -EINVAL;
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}
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lseek(fd, -4, SEEK_END);
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write(fd, &t, 4);
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lseek(fd, 0, SEEK_SET);
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while (read(fd, &t, 4) > 0)
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sum -= t;
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lseek(fd, -4, SEEK_END);
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write(fd, &sum, 4);
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close(fd);
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return 0;
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}
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