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C/C++ Source or Header  |  1988-04-27  |  4.6 KB  |  104 lines
  1. /*  ARC - Archive utility - ARCSVC
  2.  
  3. System V Version 1.0 based upon:
  4.     Version 2.15, created on 12/17/85 at 15:17:16
  5.  
  6. (C) COPYRIGHT 1985 by System Enhancement Associates; ALL RIGHTS RESERVED
  7.  
  8.     By:  Thom Henderson
  9.  
  10.     Description:
  11.          This file contains service routines needed to maintain an archive.
  12. */
  13. #include "arc.h"
  14.  
  15. INT openarc(chg)                       /* open archive */
  16. INT chg;                               /* true to open for changes */
  17. {
  18.     FILE *fopen();                     /* file opener */
  19.  
  20.     if(!(arc=fopen(arcname,"r")))
  21.     {    if(chg)
  22.               printf("Creating new archive: %s\n",arcname);
  23.          else abort("Cannot read archive: %s",arcname);
  24.     }
  25.  
  26.     if(chg)                            /* if opening for changes */
  27.          if(!(new=fopen(newname,"w")))
  28.               abort("Cannot create archive copy: %s",newname);
  29. }
  30.  
  31. INT closearc(chg)                          /* close an archive */
  32. INT chg;                               /* true if archive was changed */
  33. {
  34.     if(arc)                            /* if we had an initial archive */
  35.          fclose(arc);                  /* then close it */
  36.  
  37.     if(chg)                            /* if things have changed */
  38.     {    setstamp(new,arcdate,arctime);/* archive matches newest file */
  39.          fclose(new);                  /* close the new copy */
  40.  
  41.          if(arc)                       /* if we had an original archive */
  42.          {    if(keepbak)              /* if a backup is wanted */
  43.               {    unlink(bakname);    /* erase any old copies */
  44.                    if(rename(arcname,bakname))
  45.                         abort("Cannot rename %s to %s",arcname,bakname);
  46.                    printf("Keeping backup archive: %s\n",bakname);
  47.               }
  48.               else if(unlink(arcname))
  49.                    abort("Cannot delete old archive: %s",arcname);
  50.          }
  51.  
  52.          if(rename(newname,arcname))
  53.               abort("Cannot rename %s to %s",newname,arcname);
  54.     }
  55. }
  56.  
  57. /* CRC computation logic
  58.  
  59.    The logic for this method of calculating the CRC 16 bit polynomial
  60.    is taken from an article by David Schwaderer in the April 1985
  61.    issue of PC Tech Journal.
  62. */
  63.  
  64. static INT crctab[] =                  /* CRC lookup table */
  65. {   0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
  66.     0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
  67.     0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
  68.     0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
  69.     0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
  70.     0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
  71.     0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
  72.     0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
  73.     0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
  74.     0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
  75.     0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
  76.     0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
  77.     0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
  78.     0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
  79.     0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
  80.     0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
  81.     0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
  82.     0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
  83.     0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
  84.     0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
  85.     0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
  86.     0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
  87.     0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
  88.     0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
  89.     0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
  90.     0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
  91.     0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
  92.     0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
  93.     0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
  94.     0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
  95.     0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
  96.     0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040
  97. };
  98. INT addcrc(crc,c)                      /* update a CRC check */
  99. INT crc;                               /* running CRC value */
  100. unsigned char c;                       /* character to add */
  101. {
  102.     return (((crc>>8)&0x00ff) ^ crctab[(crc^c)&0x00ff]) & 0x0000ffff;
  103. }
  104.