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https://github.com/erkyrath/infocom-zcode-terps.git
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111 lines
2.5 KiB
C
111 lines
2.5 KiB
C
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/* Serialize.c Duncan Blanchard, 9/1/88
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This utility patches a one-byte serial number into an Infocom game file.
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The number serves as an anti-piracy device on disks sent to outside testers.
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Two possible techniques:
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- update serial number, and add (new - old) to lowcore checksum.
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This is the current implementation.
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- update serial number, and subtract (new - old) from an adjacent
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dummy byte (or even from the high-order byte). This would simplify
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the patching of multi-disk games.
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*/
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#include <types.h>
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#include <stdio.h>
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#include <ErrMgr.h>
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#include <Errors.h>
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#include <CursorCtl.h>
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/* #include <dos.h> */
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#define UWORD unsigned short /* 16 bits */
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#define CHKOFF 28 /* checksum offset in game file */
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main(argc, argv)
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int argc;
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char *argv[];
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{
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FILE *fp, *fopen();
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int i, srloff;
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UWORD srlnum, oldsrlnum, chksum;
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if (argc != 4)
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{
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fprintf(stderr, "\nusage: Serialize <filename> <srlnum (2 bytes) offset> <srlnum val (0-255)>.\n");
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exit(1);
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}
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if ((fp = fopen(argv[1], "r+")) == NULL) /* mode = read/write */
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{
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fprintf(stderr, "\nError opening file <%s>\n", argv[1]);
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exit(2);
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}
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sscanf(argv[2], "%ld", &srloff);
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sscanf(argv[3], "%hd", &srlnum);
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/* reject new values >1 byte (complicates checksum adjustment) */
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if (srlnum > 255)
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{
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fprintf(stderr, "\nError, serial number can't exceed 255\n");
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exit(3);
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}
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readword(fp, srloff, (char *) &oldsrlnum);
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/* old value should normally be 1 or 0 -- if it's NOT, user probably
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gave us a bad offset. Catch error before file is written to. */
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if (oldsrlnum > 1 /*255*/ )
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{
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fprintf(stderr, "\nError, old serial number exceeds 1");
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fprintf(stderr, "\nThe 'srlnum offset' you supplied may be wrong!\n");
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exit(4);
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}
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writeword(fp, srloff, (char *) &srlnum); /* patch in new serial number */
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readword(fp, CHKOFF, (char *) &chksum);
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chksum += (srlnum - oldsrlnum);
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writeword(fp, CHKOFF, (char *) &chksum); /* and adjust checksum */
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fclose(fp);
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printf("Done\n");
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exit(0);
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}
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readword(fp, off, bufp)
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FILE *fp;
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int off;
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char *bufp;
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{
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if (fseek(fp, off, 0) != 0)
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{
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fprintf(stderr, "\nRSeek %d error\n", off);
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exit(11);
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}
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if (fread(bufp, 1, 2, fp) != 2)
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{
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fprintf(stderr, "\nError reading file\n");
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exit(12);
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}
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}
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writeword(fp, off, bufp)
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FILE *fp;
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int off;
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char *bufp;
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{
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if (fseek(fp, off, 0) != 0)
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{
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fprintf(stderr, "\nWSeek %d error\n", off);
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exit(13);
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}
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if (fwrite(bufp, 1, 2, fp) != 2)
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{
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fprintf(stderr, "\nError writing file\n");
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exit(14);
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}
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}
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