home *** CD-ROM | disk | FTP | other *** search
/ Frozen Fish 1: Amiga / FrozenFish-Apr94.iso / bbs / alib / d0xx / d050 / unixarc.lha / UnixArc / arcsvc.c < prev    next >
Encoding:
C/C++ Source or Header  |  1987-01-17  |  4.8 KB  |  115 lines
  1. /*  ARC - Archive utility - ARCSVC
  2.  
  3. (C) COPYRIGHT 1985 by System Enhancement Associates; ALL RIGHTS RESERVED
  4.  
  5.     By:  Thom Henderson
  6.  
  7.     Description:
  8.          This file contains service routines needed to maintain an archive.
  9.  
  10.     Language:
  11.          Computer Innovations Optimizing C86
  12. */
  13. #include <stdio.h>
  14. #include "arc.h"
  15.  
  16. openarc(chg)                           /* open archive */
  17. int chg;                               /* true to open for changes */
  18. {
  19.     FILE *fopen();                     /* file opener */
  20.  
  21.     if(!(arc=fopen(arcname,"r")))
  22.     {    if(chg)
  23.               printf("Creating new archive: %s\n",arcname);
  24.          else abort("Cannot read archive: %s",arcname);
  25.     }
  26.  
  27.     if(chg)                            /* if opening for changes */
  28.          if(!(new=fopen(newname,"w")))
  29.               abort("Cannot create archive copy: %s",newname);
  30. }
  31.  
  32. closearc(chg)                          /* close an archive */
  33. int chg;                               /* true if archive was changed */
  34. {
  35.     if(arc)                            /* if we had an initial archive */
  36.          fclose(arc);                  /* then close it */
  37.  
  38.     if(chg)                            /* if things have changed */
  39.     {
  40. #if unix
  41.          fclose(new);                  /* close the new copy */
  42.          setstamp(newname,arcdate,arctime);/* archive matches newest file */
  43. #else
  44.          setstamp(new,arcdate,arctime);/* archive matches newest file */
  45.          fclose(new);                  /* close the new copy */
  46. #endif
  47.  
  48.          if(arc)                       /* if we had an original archive */
  49.          {    if(keepbak)              /* if a backup is wanted */
  50.               {    unlink(bakname);    /* erase any old copies */
  51.                    if(rename(arcname,bakname))
  52.                         abort("Cannot rename %s to %s",arcname,bakname);
  53.                    printf("Keeping backup archive: %s\n",bakname);
  54.               }
  55.               else if(unlink(arcname))
  56.                    abort("Cannot delete old archive: %s",arcname);
  57.          }
  58.  
  59.          if(rename(newname,arcname))
  60.               abort("Cannot rename %s to %s",newname,arcname);
  61.     }
  62. }
  63.  
  64. /* CRC computation logic
  65.  
  66.    The logic for this method of calculating the CRC 16 bit polynomial
  67.    is taken from an article by David Schwaderer in the April 1985
  68.    issue of PC Tech Journal.
  69. */
  70.  
  71. static int crctab[] =                  /* CRC lookup table */
  72. {   0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
  73.     0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
  74.     0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
  75.     0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
  76.     0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
  77.     0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
  78.     0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
  79.     0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
  80.     0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
  81.     0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
  82.     0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
  83.     0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
  84.     0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
  85.     0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
  86.     0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
  87.     0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
  88.     0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
  89.     0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
  90.     0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
  91.     0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
  92.     0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
  93.     0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
  94.     0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
  95.     0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
  96.     0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
  97.     0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
  98.     0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
  99.     0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
  100.     0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
  101.     0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
  102.     0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
  103.     0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040
  104. };
  105. int addcrc(crc,c)                      /* update a CRC check */
  106. int crc;                               /* running CRC value */
  107. unsigned char c;                       /* character to add */
  108. {
  109. #if unix
  110.     return (0xffff & (((crc>>8)&0x00ff) ^ crctab[(crc^c)&0x00ff]));
  111. #else
  112.     return ((crc>>8)&0x00ff) ^ crctab[(crc^c)&0x00ff];
  113. #endif
  114. }
  115.