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38 lines
720 B
C
38 lines
720 B
C
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#include <stdlib.h>
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#include <stdio.h>
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FILE *in;
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unsigned int n, i, c;
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void usage(char *arg)
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{
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printf("usage: %s [file]\n", arg);
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exit(-1);
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}
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int main(int argc, char *argv[]) {
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if (argc < 2) {
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usage(argv[0]);
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exit(-1);
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}
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if (!(in = fopen(argv[1], "r+b"))) {
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fprintf(stderr, "couldnt open: '%s'\n", argv[1]);
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exit(-1);
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}
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/* read 0x1000 bytes from 0x7000-0x7fff (offset 0x1000) */
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fseek(in, 0x1000, SEEK_SET);
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n = 0; for (i = 0; i < 0x1000; i++) {
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c = fgetc(in);
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n += c;
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}
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/* write checksum to header */
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fseek(in, 0, SEEK_SET);
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fputc(n & 0xff, in);
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fputc((n >> 8) & 0xff, in);
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fclose(in);
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return (0);
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}
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