atob.c

和Unix的compress/uncompress兼容的压缩/解压算法16位程序

/* 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
 */
/*
 *  DjG - Don Glostein
 *  made changes to code for compiling on non-unix compilers. Main changes
 *  were to the long constants. Originally, not all of them were declared
 *  as such and some compilers promoted in undefined ways. Unlink() function
 *  call moved to end. If done while file was open, on some operating systems
 *  this produced an error at best, and lost clusters at worst.
 *  Introduced code for temp_file to be not in the /tmp directory, for non
 *  unix systems. Introduced SETMODE for those operating systems that default
 *  to new line translation (text mode) for stdin/stdout buffered streams.
 *  NOTE: check the SETMODE and TEMPFILE defines. Make sure they are right for
 *  your machine.
 *  NOTE: if this code is compiled with no defines, then it will default to the
 *  unix operating system version.
 */


#include <stdio.h> /* include for all */

#ifdef MSC
#include <fcntl.h>
#include <io.h>
#define SETMODE(x) setmode(fileno((x)),O_BINARY)
#define TEMPFILE "atob.%x"
#endif

#ifdef MWC_ATARI
#define SETMODE(x) ((x)->_ff &= ~(_FASCII))
#define TEMPFILE "atob.%x"
#endif
/* following take care of unix systems */
#ifndef TEMPFILE
#define TEMPFILE "/usr/tmp/atob.%x"
#endif
#ifndef SETMODE
#define SETMODE(x)
#endif
#define reg register

#define streq(s0, s1)  strcmp(s0, s1) == 0

#define times85(x)	((((((x<<2)+x)<<2)+x)<<2)+x)

long int Ceor = 0L;
long int Csum = 0L;
long int Crot = 0L;
long int word = 0L;
int bcount = 0;
FILE *tmp_file= (FILE *)NULL;
char tmp_name[100]= {'\0'};

fatal() {
  fprintf(stderr, "bad format or Csum to atob\n");
  if (tmp_file != (FILE *)NULL)
      unlink(tmp_name);
  exit(1);
}

#define DE(c) ((c) - '!')

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, tmp_file);
}

main(argc, argv)
  char **argv;
{
  reg c;
  reg long int i;
  int ret;
  char buf[100];
  long int n1, n2, oeor, osum, orot;

  if (argc != 1) {
    fprintf(stderr,"bad args to %s\n", argv[0]);
    exit(2);
  }
  sprintf(tmp_name,TEMPFILE,getpid());
  tmp_file = fopen(tmp_name, "w+");
  if (tmp_file == NULL) {
    perror("couldn't open temp file");
    fatal();
  }
  else {  /* successful opens, reset mode on text conversion systems */
    SETMODE(stdin);
    SETMODE(tmp_file);
    SETMODE(stdout);
  }

  /*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((ret= scanf("btoa End N %ld %lx E %lx S %lx R %lx\n",
         &n1, &n2, &oeor, &osum, &orot)) != 5) {
            fprintf(stderr,"\nscanf returned %d",ret);
    fatal();
  }
  if ((n1 != n2) || (oeor != Ceor) || (osum != Csum) || (orot != Crot)) {
    fatal();
  } else {
    /*copy OK tmp file to stdout*/;
    fseek(tmp_file, 0L, 0);
    for (i = n1; --i >= 0;) {
      putchar(getc(tmp_file));
    }
  }
  unlink(tmp_name); /* Make file disappear */
  exit(0);
}