Little/Big Endian

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3 total messages Started by Endian Wed, 12 Apr 2006 15:29

#2449

Author: Endian
Date: Wed, 12 Apr 2006 15:29

27 lines
1711 bytes

Assume that we want to communicate (a) via RS232 and  (b) via ethernet 
between a PC and an ARM based embedded controller unit (and/or a PDA)

Assume that most of the communication consist of transmitting/receiving of 
messages similar to the following structure. Also assume that both PC 
application and ARM application use the same header files for the messages.

typedef struct {
     short int    A;
     int            B;
     float        C;
     double    D;
     unsigned char  E;
}MyStruct;


Becasue Pentium processor in PC and ARM processor in the embedded unit use 
different endians (litte & big endians) the byte orders in the transmitted 
and received structures will be different.

How to solve this little/big endian problem?

How to make PC application send/receive structures to a ARM based embedded 
unit  (a) via RS232 and  (b) via ethernet between without worrying about the 
endians?

Regards.

Re: Little/Big Endian

#2450

Author: Remy Lebeau (TeamB)
Date: Wed, 12 Apr 2006 16:28

20 lines
1717 bytes

<Endian> wrote in message news:443d1ceb$1@newsgroups.borland.com...

> Becasue Pentium processor in PC and ARM processor in the
> embedded unit use different endians (litte & big endians) the byte
> orders in the transmitted and received structures will be different.
>
> How to solve this little/big endian problem?

It is common practice to always transmit data over the network in 'network
byte order' only.  That way, the format of the data is standardized across
platforms.  On each endpoint of the connection, the software running on that
machine can convert the data to/from its local 'host byte order' as needed.

Look at the socket API htons() and htonl() functions for converting values
to 'network byte order', and ntohs() and ntohl() for converting them back to
'host byte order'.


Gambit

Re: Little/Big Endian

#2454

Author: JF Jolin
Date: Wed, 12 Apr 2006 22:32

15 lines
1215 bytes

The following article is about Writing Endian Independent Code in C++

http://www.gamedev.net/reference/articles/article2091.asp


13 Apr 2006 01:29:47 +1000, <Endian> wrote:

> How to solve this little/big endian problem?
>
> How to make PC application send/receive structures to a ARM based embedded unit
> (a) via RS232 and  (b) via ethernet between without worrying about the endians?
>

-- 
JF Jolin

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