/* atob: version 4.0 * stream filter to change printable ascii from "btoa" back into 8 bit bytes * if bad chars, or Csums do not match: exit(1) [and NO output] * * Paul Rutter Joe Orost * philabs!per petsd!joe * Fred Fish (change into pure filter, always output) */ #include #define reg register #define streq(s0, s1) strcmp(s0, s1) == 0 #define times85(x) ((((((x<<2)+x)<<2)+x)<<2)+x) long int Ceor = 0; long int Csum = 0; long int Crot = 0; long int word = 0; long int bcount = 0; #define DE(c) ((c) - '!') fatal() { fprintf(stderr, "bad format or Csum to atob\n"); exit(1); } decode(c) reg c; { if (c == 'z') { if (bcount != 0) { fatal(); } else { byteout(0); byteout(0); byteout(0); byteout(0); } } else if ((c >= '!') && (c < ('!' + 85))) { if (bcount == 0) { word = DE(c); ++bcount; } else if (bcount < 4) { word = times85(word); word += DE(c); ++bcount; } else { word = times85(word) + DE(c); byteout((int)((word >> 24) & 255)); byteout((int)((word >> 16) & 255)); byteout((int)((word >> 8) & 255)); byteout((int)(word & 255)); word = 0; bcount = 0; } } else { fatal(); } } byteout(c) reg c; { Ceor ^= c; Csum += c; Csum += 1; if ((Crot & 0x80000000)) { Crot <<= 1; Crot += 1; } else { Crot <<= 1; } Crot += c; putc(c, stdout); } main(argc, argv) char **argv; { reg c; char buf[100]; long int n1, n2, oeor, osum, orot; if (argc != 1) { fprintf(stderr,"bad args to %s\n", argv[0]); exit(2); } /*search for header line*/ for (;;) { if (fgets(buf, sizeof buf, stdin) == NULL) { fatal(); } if (streq(buf, "xbtoa Begin\n")) { break; } } while ((c = getchar()) != EOF) { if (c == '\n') { continue; } else if (c == 'x') { break; } else { decode(c); } } if(scanf("btoa End N %ld %lx E %lx S %lx R %lx\n", &n1, &n2, &oeor, &osum, &orot) != 5) { fatal(); } if ((n1 != n2) || (oeor != Ceor) || (osum != Csum) || (orot != Crot)) { fatal(); } exit(0); }