Specify a 'wire format' and read and write that format from and to a buffer when
receiving or sending.
Make sure your 'wire format' specifies byte ordering for multibyte values.
You have two issues here:
structure member alignment and padding
byte ordering
Generally it is easier to do it 'the hard way' (read and write to a buffer) than try
to be cute and invoke
all the various pragmas and compiler voodoo you need to get the structures to line up
identically
across multiple architectures and compilers.
I once maintained a piece of code which did network communication by reading and
writing directly into
structures the way you're trying to do it. It supported 10 compilers across 6
architectures and 4 operating
systems. It was not pretty, and I don't recommend anyone ever do it that way by
choice.
"Jane B. Halfond" wrote:
> Hi,
>
> I'm currently writing a bitmap compression routine and trying to send a byte
> stream which behind the scenes contains a structure of information (see
> below). This byte stream is being sent from the PC to the Palm. I know
> there's a problem with byte alignment with structures and therefore, tried
> to byte swap the information on both sides. For some reason, something
> isn't working right. Does anyone have any suggestions for sending
> structures as byte streams from the PC to the Palm.
>
> Note: Either a byte stream of a CompARecordType record is being sent to the
> Palm or of type CompNoneRecordType.
>
> I'm using MSVC++ v6 and Metrowerks for Palm development v6.
>
> Thanks,
> Jane
>
> ---
> Jane Halfond
> Synergy Solutions, Inc.
> http://www.synsolutions.com
> a BarPoint.com Company
> http://www.barpoint.com
> 1-212-461-2292
>
> // Because MSVC doesn't support UInt8, we need to use byte
> #ifdef MSVC_COMPILED
> #define UInt8 byte
> #endif
>
> enum CompStyle { eCompNone = 0, eCompA };
>
> typedef struct CompHeaderTypeTag
> {
> CompStyle eCompStyle;
> unsigned long rawSize; // raw size of the uncompressed data
> unsigned long numBlocks; // number of CompATypes appearing in the
> compressed structure
> } CompHeaderType;
>
> typedef struct CompABlockTypeTag
> {
> UInt8 token;
> UInt8 repeat;
> } CompABlockType;
>
> typedef struct CompARecordTypeTag
> {
> CompHeaderType hdr;
> CompABlockType blocks[];
> } CompARecordType;
>
> typedef struct CompNoneRecordTypeTag
> {
> CompHeaderType hdr;
> UInt8 buffer[];
> } CompNoneRecordType;
>
> --
> For information on using the Palm Developer Forums, or to unsubscribe, please see
>http://www.palmos.com/dev/tech/support/forums/
--
Adam Wozniak Senior Software Design Engineer
Surveyor Corporation
[EMAIL PROTECTED] 4548 Broad Street
[EMAIL PROTECTED] San Luis Obispo, CA 93401
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