Re: Marshalling Message??

From: Stefan Höhne (do_not_use_this_adress_at_127.0.0.1)
Date: 11/11/03 

Date: Tue, 11 Nov 2003 15:58:32 +0100

Hi,

"Terence" <findty@hotmail.com> wrote in message
news:0rYrb.17623$HoK.16118@news01.bloor.is.net.cable.rogers.com...
> Help Need!!!

who's Need?

> I am writing a program for a distributed system course.
> I need to marshall all the messages in order to send them thru a socket.
> The first 8 bytes of the message are used to store the length of the
message,

8 Byte? Your're prepared for the future ...

> and then the rest are the actual content of the message.
> So I have a big char array, what is the easiest way to store an 8-byte
integer
> across the first 8 characters in the array?

Depends on how you represent an 8-byte-integer in memory, thus: depends on
what
is the input.

> For Examples:
>
> Integer 1:
> 00 00 00 00 00 00 00 01 ...
>
> Integer 10:
> 00 00 00 00 00 00 00 0A ...
>
> Integer 256:
> 00 00 00 00 00 00 01 00 ...
>
> I don't want to calculate each of the byte

But: this would be the cleanest and most portable solution.

... and not that hard (if theres a shift operation on
    your input) ...

#include <algorithm>
#include <iterator>
#include <iostream>
#include <iomanip>

int main() {
  long long int length=266;
  char message[10] = {0};
  int i=9;

  while ((length>0) && (i>=0)) {
    message[i]=length;
    length>>=8;
    --i;
  }
  std::cout << std::hex;
  std::copy(message, message+10, std::ostream_iterator<int>(std::cout, "
"));
}

Output:
0 0 0 0 0 0 0 0 1 a

> How do I put the integer in this array??

OK?

As others suggested, using standard posix functions
would be ok, too: but I doubt they'll be defined for
a 64bit integer.

HTH,
Stefan.

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