Source Code 1994 March/Source_Code_CD-ROM_Walnut_Creek_March_1994.iso/compsrcs/misc/volume28/crc16/part01

Text File | 1992-03-14 | 4.9 KB | 172 lines

Newsgroups: comp.sources.misc
From: [e-mail] (Hendrik Boom)
Subject:  v28i102:  crc16 - Generate 16-bit CRC checksums, Part01/01
Message-ID: <[e-mail]>
X-Md4-Signature: 1d1f174f0fd424312de82f1fa3e9d55f
Date: Sat, 14 Mar 1992 22:39:29 GMT
Approved: [e-mail]

Submitted-by: [e-mail] (Hendrik Boom)
Posting-number: Volume 28, Issue 102
Archive-name: crc16/part01
Environment: UNIX, Amiga

I wrote this a few years ago. It's useful for checking that file transfers
work properly.

How to use it?
Say
    crc  filenames
and get crc check values for the files on standard output, in hex and decimal.

It uses the CCITT 16-bit CRC polynomial.

    -- hendrik.
----
#! /bin/sh
# This is a shell archive.  Remove anything before this line, then feed it
# into a shell via "sh file" or similar.  To overwrite existing files,
# type "sh file -c".
# The tool that generated this appeared in the comp.sources.unix newsgroup;
# send mail to [e-mail] if you want that tool.
# Contents:  crc.c crc.makefile make_crc_tab.c
# Wrapped by kent@sparky on Sat Mar 14 16:32:35 1992
PATH=/bin:/usr/bin:/usr/ucb ; export PATH
echo If this archive is complete, you will see the following message:
echo '          "shar: End of archive 1 (of 1)."'
if test -f 'crc.c' -a "${1}" != "-c" ; then
  echo shar: Will not clobber existing file \"'crc.c'\"
else
  echo shar: Extracting \"'crc.c'\" \(1087 characters\)
  sed "s/^X//" >'crc.c' <<'END_OF_FILE'
X/* The following routines can be used to interpret the crc_table.
X  First use init_crc; then add_crc for each character, from
X  first to last; and finally, as report_crc to yield the
X  result. It is probably much more convenient to code these
X  routines inline; this file serves primarily as documentation. */
X#include <stdio.h>
X#include "crc_tab.h"
X
Xstatic unsigned short crc;
X
Xvoid init_crc(){crc = 0;}
X
Xvoid add_crc(c) unsigned char c;
X  {crc = crc_table[(crc & 0x00ff) ^ c] ^ (crc >> 8);
X  }
X
Xunsigned short report_crc(){return crc;}
X
Xvoid crcfile(name)char *name;
X {FILE *f; int c; unsigned short ck;
X  printf("crc %s ", name);
X  f = fopen(name, "rb");
X  if(! f){printf("cannot find %s\n", name); return;}
X  init_crc();
X  while((c = getc(f)) >= 0){add_crc(c);}
X  ck =  report_crc();
X#ifdef AMIGA
X  printf("0x%x %d\n", ck, ck);
X#else
X  printf("%#.4x %d\n", ck, ck);
X#endif
X  fclose(f);
X  return;
X }
X
Xvoid main(argc, argv)int argc; char *argv[];
X {int i; char **c;
X  if(argc < 2){printf("crc filenames\n"); exit(1);}
X  c = &(argv[1]); i=argc;
X  while(--i)crcfile(*c++);
X  exit(0);
X }
END_OF_FILE
  if test 1087 -ne `wc -c <'crc.c'`; then
    echo shar: \"'crc.c'\" unpacked with wrong size!
  fi
  # end of 'crc.c'
fi
if test -f 'crc.makefile' -a "${1}" != "-c" ; then
  echo shar: Will not clobber existing file \"'crc.makefile'\"
else
  echo shar: Extracting \"'crc.makefile'\" \(211 characters\)
  sed "s/^X//" >'crc.makefile' <<'END_OF_FILE'
X$(SYSTYPE)/make_crc_tab : make_crc_tab.c
X    cc make_crc_tab.c -o $(SYSTYPE)/make_crc_tab
Xcrc_tab.h : make_crc_tab
X    ./$(SYSTYPE)/make_crc_tab >crc_tab.h
X$(SYSTYPE)/crc : crc.c crc_tab.h
X    cc crc.c -o $(SYSTYPE)/crc
END_OF_FILE
  if test 211 -ne `wc -c <'crc.makefile'`; then
    echo shar: \"'crc.makefile'\" unpacked with wrong size!
  fi
  # end of 'crc.makefile'
fi
if test -f 'make_crc_tab.c' -a "${1}" != "-c" ; then
  echo shar: Will not clobber existing file \"'make_crc_tab.c'\"
else
  echo shar: Extracting \"'make_crc_tab.c'\" \(809 characters\)
  sed "s/^X//" >'make_crc_tab.c' <<'END_OF_FILE'
X/* The CRC polynomial is represented in binary; each bit is the
Xcoefficient of a term. The low-order bit corresponds to the
Xhighest-order coefficient (yes, this does seem backwards).
X
XThe bit sequences for some common CRC polynomials:
X
XCRC-16:     16    15    2
X    x   + x   + x  + 1    0x14003
X
XCCITT:     16    12    5
X    x   + x   + x  + 1    0x10811
X
XThe CCITT polynomial is used for Kermit.
X
X*/
X
X#define CCITT 0x10811
X#define CRC_16 0x14003
X
Xvoid make_16_bit_crc_tab(poly) unsigned int poly;
X  {unsigned int i,j, M;
X  printf("unsigned short crc_table[256] = {\n");
X  for (i=0; i<256; i++){
X    M = i;
X    for (j=8;j>0;j--){
X      if (M & 1){M ^= poly;}
X      M >>= 1;}
X#ifdef AMIGA
X    printf("0x%x,\n", M);
X#else
X    printf("%#x,\n", M);
X#endif
X    }
X  printf("};\n");
X}
X
Xvoid main(){make_16_bit_crc_tab(CCITT);}
END_OF_FILE
  if test 809 -ne `wc -c <'make_crc_tab.c'`; then
    echo shar: \"'make_crc_tab.c'\" unpacked with wrong size!
  fi
  # end of 'make_crc_tab.c'
fi
echo shar: End of archive 1 \(of 1\).
cp /dev/null ark1isdone
MISSING=""
for I in 1 ; do
    if test ! -f ark${I}isdone ; then
    MISSING="${MISSING} ${I}"
    fi
done
if test "${MISSING}" = "" ; then
    echo You have the archive.
    rm -f ark[1-9]isdone
else
    echo You still must unpack the following archives:
    echo "        " ${MISSING}
fi
exit 0
exit 0 # Just in case...