70 lines
1.5 KiB
C
70 lines
1.5 KiB
C
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/* McPhail's Tip-Top TAP Top-Tailer
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* Takes a raw code file as input
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* Prepends data length and appends xor checksum
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* Outputs to new file with .block suffix */
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <linux/limits.h>
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#include <string.h>
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int main(int argc, char *argv[])
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{
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int fdin, fdout;
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char outfilename[PATH_MAX];
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unsigned int count = 0;
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unsigned char tally = 0;
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unsigned char next = 0;
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if (argc!=2) {
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printf("Please specify file to read.\n");
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return -1;
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}
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fdin = open(argv[1], O_RDONLY);
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if (fdin<0) {
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printf("Couldn't open %s. for reading\n", argv[1]);
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return -1;
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}
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snprintf(outfilename, PATH_MAX, "%s.block", argv[1]);
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outfilename[PATH_MAX - 1] = '\0';
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if (! strcmp(argv[1], outfilename)) {
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printf("Filename too long - would clobber existing.\n");
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close(fdin);
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return -1;
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}
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fdout = open(outfilename, O_CREAT|O_WRONLY|O_TRUNC, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH);
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if (fdout<0) {
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printf("Couldn't open %s for writing.\n", outfilename);
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close(fdin);
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return -1;
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}
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while (read(fdin, &next, 1)) {
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tally ^= next;
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count ++;
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};
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lseek(fdin, 0, SEEK_SET);
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char lsb = (count+1)&255;
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char msb = ((count+1)>>8)&255;
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write(fdout, &lsb, 1);
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write(fdout, &msb, 1);
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while (read(fdin, &next, 1)) {
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write(fdout, &next, 1);
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}
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write(fdout, &tally, 1);
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close(fdout);
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close(fdin);
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printf("File %s written.\n", outfilename);
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printf("Code length including first byte is %d (0x%.4X).\n", count, count);
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printf("Removing first byte gives 0x%.4X.\n", count-1);
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return 0;
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}
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