From:	CRDGW2::CRDGW2::MRGATE::"SMTP::CRVAX.SRI.COM::RELAY-INFO-VAX" 13-AUG-1990 14:33:18.05
To:	MRGATE::"ARISIA::EVERHART"
CC:	
Subj:	Re: PBMPLUS problems with PCX and GIF files

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Date: 13 Aug 90 17:41:11 GMT
From: psuvm!psuecl!praxa!ttt@psuvax1.cs.psu.edu  (Trevor Taylor)
Organization: Praxa Ltd.
Subject: Re: PBMPLUS problems with PCX and GIF files
Message-Id: <65378@praxa.com.au>
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In article <"900809173026.76366.323.EHL28-4"@CompuServe.COM>, 76366.323@CompuServe.COM (Level Five Research) writes:
>>I have been trying to get PBMPLUS working with files copied up from a PC,
>>however have met with little success.
>>
>>Creating a two colour (i.e. B/W) picture with Microsoft Paintbrush, copying
>>the resulting file up to the VAX using PCSA, and typing :-
>
> How is the file service that you're using under PCSA set up?  Is it creating
> FIXED length files, or STREAM files?  For some programs, it does make a
> difference.
>

Specifically, the problem is as follows:

The default file type for PCSA is STREAM. The VAX C run-time library
does not handle STREAM files correctly (it uses STREAM_LF). There are
three ways around the problem:

1. Set your file service up to use FIXED files (512 bytes). VAX-C
reads these OK.

2. Get a copy of the FILE utility from DECUS and use it to change
the file attributes from STREAM to STREAM_LF. (NOTE: There is
absolutely nothing wrong with the data in the file -- it is just
the file attributes which cause VAX-C to access it incorrectly.)

3. Change the code so that you force it to open the files with
a context of STREAM as follows:
        fopen(fp,file,"r","ctx=stm");
This is a VAX extension and is non-portable. Furthermore, if you
use this approach, then the normal interpretation of other file
types, including sequential, indexed, etc., does not happen.
In fact, it reads EVERY byte in the file!!!

The reason for this problem has to do with the way that VAX-C
converts record-oriented files into a stream of bytes for
reading. This is necessary for normal files, such as those
created with EDT, to be read correctly. Unfortunately, it does
not understand STREAM, only STREAM_LF.

Maybe somebody at DEC would care to explain this apparent
inconsistency?

        Trevor