Date: Thu, 19 Dec 96 01:03:10 GMT
From: "Adrian Martin" <adrian DOT martin AT ypn DOT co DOT uk>
Encoding: 44 Text
Message-Id: <9611198509.AA850988002@ypn.co.uk>
To: djgpp AT delorie DOT com
Cc: an118 AT chebucto DOT ns DOT ca
Subject: RE:NEED HELP reading header for pcx image file

>>         I have written code that seems to read in the first 128 bytes,
>> which is the header for the pcx file. But when I look at it, it's
>> gobble-de-gook, you can't read it. I've even tried reading it as a pcx
>> structure. All my reads were done on the file opened in binary mode. Once
>> I read in the header via binary, it even shows as garbage when I try to
>> access individual header elements via my structure member variable after
>> reading it into the structure. Can anybody tell me what's wrong?
>
>Take a look at the PCX code on my page.  It's written for DJGPP.
>
>My guess is that you're missing a "__attribute__ ((packed))"
>somewhere...
>
I've had the same problem, my solutions is :- The place you copied the structure 
of the PCX header struct from assumed 16 bit INTs whilst DJGPP/GNU C uses 32 bit 
ints. So just change any variable initialises from:-

    typedef struct
        {
            :
            :
            :
            unsigned int xmax;
            unsigned int xmin;
            :               // i cannot remember the rest of the structure
            :
        }PCX_header,*PCX_header_ptr;

TO:
typedef struct
        {
            :
            :
            :
            unsigned short int xmax;    //shorts are 16 bits in DJGPP
            unsigned short int xmin;    //the bit sizes of variable types       
            :                      ;    //can be found in the djsizes.h
            :
            :
        }PCX_header,*PCX_header_ptr;


Adrian Martin.