Placing bytes into a stream

[Jonathan Halterman]

I have a pointer to a buffer of bytes that I receive from a tcp stream that
I would like to place into some kind of stream that can I can then use to
serialize the data into into individual variables. I looked at the
streambuf, istream, and strstream, and can't quite figure out a simple
implementation for what I need.

Given a pointer to a buffer of bytes, and the size of the bytes that I am
concerned with, how can I get this into a stream that I can then use to
serialize the data to individual variables? The data is organized such that
there are two long values (4 bytes each), followed by two integers, then a
20 byte string of characters, etc...

jonathan

[Mike Wahler]

Re: Placing bytes into a stream


"Jonathan Halterman" <nix@aol.com> wrote in message
news:vorrftkh99 u9bc@corp.super news.com...[color=blue]
> I have a pointer to a buffer of bytes that I receive from a tcp stream[/color]
that[color=blue]
> I would like to place into some kind of stream that can I can then use to
> serialize the data into into individual variables.[/color]

This is *de*serializati on.
[color=blue]
>I looked at the
> streambuf, istream, and strstream, and can't quite figure out a simple
> implementation for what I need.
>
> Given a pointer to a buffer of bytes, and the size of the bytes that I am
> concerned with, how can I get this into a stream that I can then use to
> serialize the data to individual variables? The data is organized such[/color]
that[color=blue]
> there are two long values (4 bytes each), followed by two integers, then a
> 20 byte string of characters, etc...
>
> jonathan
>
>[/color]

By definition, the size of a char is one byte in C++.
If the number of bits per char in the buffer don't
match your implementation' s type 'char' number of bits,
you'll need to do a conversion.

I'm assuming your description above is indicating that
your implementation' s type 'long' is actually 4 bytes
in size, and that the 'int' types in the buffer also
match the size for your implementation.

You may also need to 'fix up' the byte ordering
(e.g. 'big-endian', 'little-endian')

#include <algorithm>
#include <iostream>

void foo(const char* buffer)
{
const long *pl(reinterpret _cast<long*>(bu ffer));
long L1 = *pl++;
long L2 = *pl++;

const int *pi(reinterpret _cast<int*>(pl) ;
int I1 = *pi++;
int I2 = *pi++;

const char *p = reinterpret_cas t<char *>(pi);
char array[21] = {0}
std:: copy(p, p + 20, array);

std::cout << L1 << '\n'
<< L2 << '\n'
<< I1 << '\n'
<< I2 << '\n'
<< array << '\n';
}

Not tested.

-Mike

[Jonathan Halterman]

Re: Placing bytes into a stream

Thanks for the example Mike. I will give this "deserializatio n" method a
try.

jonathan

"Mike Wahler" <mkwahler@mkwah ler.net> wrote in message
news:nFmjb.2557 $s93.1280@newsr ead3.news.pas.e arthlink.net...[color=blue]
>
> "Jonathan Halterman" <nix@aol.com> wrote in message
> news:vorrftkh99 u9bc@corp.super news.com...[color=green]
> > I have a pointer to a buffer of bytes that I receive from a tcp stream[/color]
> that[color=green]
> > I would like to place into some kind of stream that can I can then use[/color][/color]
to[color=blue][color=green]
> > serialize the data into into individual variables.[/color]
>
> This is *de*serializati on.
>[color=green]
> >I looked at the
> > streambuf, istream, and strstream, and can't quite figure out a simple
> > implementation for what I need.
> >
> > Given a pointer to a buffer of bytes, and the size of the bytes that I[/color][/color]
am[color=blue][color=green]
> > concerned with, how can I get this into a stream that I can then use to
> > serialize the data to individual variables? The data is organized such[/color]
> that[color=green]
> > there are two long values (4 bytes each), followed by two integers, then[/color][/color]
a[color=blue][color=green]
> > 20 byte string of characters, etc...
> >
> > jonathan
> >
> >[/color]
>
> By definition, the size of a char is one byte in C++.
> If the number of bits per char in the buffer don't
> match your implementation' s type 'char' number of bits,
> you'll need to do a conversion.
>
> I'm assuming your description above is indicating that
> your implementation' s type 'long' is actually 4 bytes
> in size, and that the 'int' types in the buffer also
> match the size for your implementation.
>
> You may also need to 'fix up' the byte ordering
> (e.g. 'big-endian', 'little-endian')
>
> #include <algorithm>
> #include <iostream>
>
> void foo(const char* buffer)
> {
> const long *pl(reinterpret _cast<long*>(bu ffer));
> long L1 = *pl++;
> long L2 = *pl++;
>
> const int *pi(reinterpret _cast<int*>(pl) ;
> int I1 = *pi++;
> int I2 = *pi++;
>
> const char *p = reinterpret_cas t<char *>(pi);
> char array[21] = {0}
> std:: copy(p, p + 20, array);
>
> std::cout << L1 << '\n'
> << L2 << '\n'
> << I1 << '\n'
> << I2 << '\n'
> << array << '\n';
> }
>
> Not tested.
>
> -Mike
>
>[/color]

[Jonathan Mcdougall]

Re: Placing bytes into a stream

>>> I have a pointer to a buffer of bytes that I receive from a tcp[color=blue][color=green][color=darkred]
>>> stream that I would like to place into some kind of stream that can
>>> I can then use to serialize the data into into individual variables.[/color]
>>
>> This is *de*serializati on.
>>[/color]
> Thanks for the example Mike. I will give this "deserializatio n"
> method a try.[/color]


Please do not top-post.

http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.4

Jonathan

[Mike Wahler]

Re: Placing bytes into a stream

"Mike Wahler" <mkwahler@mkwah ler.net> wrote in message
news:nFmjb.2557 $s93.1280@newsr ead3.news.pas.e arthlink.net...[color=blue]
>
> void foo(const char* buffer)
> {
> const long *pl(reinterpret _cast<long*>(bu ffer));[/color]

const long *pl = reinterpret_cas t<long*>(buffer );
[color=blue]
> long L1 = *pl++;
> long L2 = *pl++;
>
> const int *pi(reinterpret _cast<int*>(pl) ;[/color]

const int *pi = reinterpret_cas t<int*>(pl);
[color=blue]
> Not tested.[/color]

Or compiled. :-)

-Mike

[Jonathan Halterman]

Re: Placing bytes into a stream


"Jonathan Mcdougall" <jonathanmcdoug all@DELyahoo.ca > wrote in message
news:CJpjb.6050 $rj4.448988@web er.videotron.ne t...[color=blue][color=green][color=darkred]
> >>> I have a pointer to a buffer of bytes that I receive from a tcp
> >>> stream that I would like to place into some kind of stream that can
> >>> I can then use to serialize the data into into individual variables.
> >>
> >> This is *de*serializati on.
> >>[/color]
> > Thanks for the example Mike. I will give this "deserializatio n"
> > method a try.[/color]
>
>
> Please do not top-post.
>
> http://www.parashift.com/c++-faq-lit...t.html#faq-5.4[/color]

Bet you were waiting all week to say that to someone. Well done.

jonathan