From:	CSBVAX::MRGATE!info-vax-RELAY@KL.SRI.COM@SMTP 18-JUL-1988 03:43
To:	ARISIA::EVERHART
Subj:	Problems with C I/O


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Date:     Tue, 12 Jul 88 16:33 CDT
From:     <KIERSTEI%UMKCVAX1.BITNET@CUNYVM.CUNY.EDU>
Subject:  Problems with C I/O
To:       info-vax@kl.sri.com
X-Original-To:  info-vax@kl.sri.com, KIERSTEIN

Info-VAXers,

    I've found a problem as I was converting ARC to run on the VAX.  I
converted the code, and generated some archives, but then when I tried to
extract the entries, some of the entries failed the checksum test.  Upon
investigation, I found that the archive entry for that file was all
binary zeros!  Several other entries in this particular archive as well
as other entries in other archives were the same way.

    In checking out the problem, I noticed that on the first archive, that
the bad entry started at A6E02 (printed by ftell()).  With the same executable,
I shortened the filenames (I changed the files in the headers to strings), and
when the entry started on A6DFF or less, the entry was perfect!  If greater
or equal to A6E00, then binary zeros!  The following header and entry were
in fine shape.

    The code involved is a tight loop copying a file from a scratch file to
the archive (in arcpack.c).  Something like

    while ((c = fgetc(crn)) != EOF) fputc (c, f);

    In this loop, I inserted the following:

i = ftell(f);         /* Where are we? */
fputc (c, f);         /* Output byte   */
fseek (f, i, 0);      /* Go to where we were */
if (c != fgetc(f)) printf ("Error in copying to archive at %d\n", i);

    The error message never was written!  I also put come code in there to
print out every nth character, and it did, but close the file and leave,
binary zeros.  I converted all the I/O to fopen, fclose, fgetc, fputc, ftell
and fseek, but no dice.  I fflushed the file after every character in the
loop, no dice.  I fclosed and reopened the file before the loop, no dice.
I played with fseeking to the beginning of the file, then back to EOF, but
no dice.

    Any ideas for a frustrated person?  If you have a version of ARC for the
VAX, make sure that your entries check out (arc t archive).

                                        Barry Kierstein
                                        Computing Services
                                        University of Missouri - Kansas City
                                        Kierstei@Umkcvax1.Bitnet