diplodocus.org Git - nmh/blob - docs/historical/mh-6.8.5/miscellany/compress-4.0/atob.c

   1 /* atob: version 4.0
   2  * stream filter to change printable ascii from "btoa" back into 8 bit bytes
   3  * if bad chars, or Csums do not match: exit(1) [and NO output]
   4  *
   5  *  Paul Rutter         Joe Orost
   6  *  philabs!per         petsd!joe
   7  */
   8
   9 #include <stdio.h>
  10
  11 #define reg register
  12
  13 #define streq(s0, s1)  strcmp(s0, s1) == 0
  14
  15 #define times85(x)      ((((((x<<2)+x)<<2)+x)<<2)+x)
  16
  17 long int Ceor = 0;
  18 long int Csum = 0;
  19 long int Crot = 0;
  20 long int word = 0;
  21 long int bcount = 0;
  22
  23 fatal() {
  24   fprintf(stderr, "bad format or Csum to atob\n");
  25   exit(1);
  26 }
  27
  28 #define DE(c) ((c) - '!')
  29
  30 decode(c)
  31   reg c;
  32 {
  33   if (c == 'z') {
  34     if (bcount != 0) {
  35       fatal();
  36     } else {
  37       byteout(0);
  38       byteout(0);
  39       byteout(0);
  40       byteout(0);
  41     }
  42   } else if ((c >= '!') && (c < ('!' + 85))) {
  43     if (bcount == 0) {
  44       word = DE(c);
  45       ++bcount;
  46     } else if (bcount < 4) {
  47       word = times85(word);
  48       word += DE(c);
  49       ++bcount;
  50     } else {
  51       word = times85(word) + DE(c);
  52       byteout((int)((word >> 24) & 255));
  53       byteout((int)((word >> 16) & 255));
  54       byteout((int)((word >> 8) & 255));
  55       byteout((int)(word & 255));
  56       word = 0;
  57       bcount = 0;
  58     }
  59   } else {
  60     fatal();
  61   }
  62 }
  63
  64 FILE *tmp_file;
  65
  66 byteout(c)
  67   reg c;
  68 {
  69   Ceor ^= c;
  70   Csum += c;
  71   Csum += 1;
  72   if ((Crot & 0x80000000)) {
  73     Crot <<= 1;
  74     Crot += 1;
  75   } else {
  76     Crot <<= 1;
  77   }
  78   Crot += c;
  79   putc(c, tmp_file);
  80 }
  81
  82 main(argc, argv)
  83   char **argv;
  84 {
  85   reg c;
  86   reg long int i;
  87   char tmp_name[100];
  88   char buf[100];
  89   long int n1, n2, oeor, osum, orot;
  90
  91   if (argc != 1) {
  92     fprintf(stderr,"bad args to %s\n", argv[0]);
  93     exit(2);
  94   }
  95   sprintf(tmp_name, "/usr/tmp/atob.%x", getpid());
  96   tmp_file = fopen(tmp_name, "w+");
  97   if (tmp_file == NULL) {
  98     fatal();
  99   }
 100   unlink(tmp_name);     /* Make file disappear */
 101   /*search for header line*/
 102   for (;;) {
 103     if (fgets(buf, sizeof buf, stdin) == NULL) {
 104       fatal();
 105     }
 106     if (streq(buf, "xbtoa Begin\n")) {
 107       break;
 108     }
 109   }
 110
 111   while ((c = getchar()) != EOF) {
 112     if (c == '\n') {
 113       continue;
 114     } else if (c == 'x') {
 115       break;
 116     } else {
 117       decode(c);
 118     }
 119   }
 120   if(scanf("btoa End N %ld %lx E %lx S %lx R %lx\n",
 121          &n1, &n2, &oeor, &osum, &orot) != 5) {
 122     fatal();
 123   }
 124   if ((n1 != n2) || (oeor != Ceor) || (osum != Csum) || (orot != Crot)) {
 125     fatal();
 126   } else {
 127     /*copy OK tmp file to stdout*/;
 128     fseek(tmp_file, 0L, 0);
 129     for (i = n1; --i >= 0;) {
 130       putchar(getc(tmp_file));
 131     }
 132   }
 133   exit(0);
 134 }