how to return a char array

[Ger]

Hi,

I have been trying to return a data packet (as a char array) at the end of a
function but that seems to be impossible...
I would like to use this char array in a different class..anyone some ideas?

greetz,
Ger

[Nick Hounsome]

Re: how to return a char array


"Ger" <g.inberg@geens pam.student.utw ente.nl> wrote in message
news:bv3hfo$3se $1@ares.cs.utwe nte.nl...[color=blue]
> Hi,
>
> I have been trying to return a data packet (as a char array) at the end of[/color]
a[color=blue]
> function but that seems to be impossible...
> I would like to use this char array in a different class..anyone some[/color]
ideas?[color=blue]
>
> greetz,
> Ger
>[/color]

You can either:
1 return a char* pointer to an array (better not be an automatic one).
2 create a struct with an array in it and return one of those (almost
certainly a bad idea)
3. pass in a reference to a std::vector and fill it (pprobably the best bet
without knowing more)

[osmium]

Re: how to return a char array

Ger writes:
[color=blue]
> I have been trying to return a data packet (as a char array) at the end of[/color]
a[color=blue]
> function but that seems to be impossible...
> I would like to use this char array in a different class..anyone some[/color]
ideas?

Allocate space for the char array, using new, in some function *before*
calling the 'data packet' function. Pass a pointer to this array around
until its meaningful lifetime has expired. Then delete it with delete. The
assignment and deletion do not have to be performed in the same function.

[Mike Wahler]

Re: how to return a char array

"Ger" <g.inberg@geens pam.student.utw ente.nl> wrote in message
news:bv3hfo$3se $1@ares.cs.utwe nte.nl...[color=blue]
> Hi,
>
> I have been trying to return a data packet (as a char array) at the end of[/color]
a[color=blue]
> function but that seems to be impossible...[/color]

Right. Passing and returning arrays to/from functions is
not allowed. Pass a pointer instead.
[color=blue]
> I would like to use this char array in a different class..anyone some[/color]
ideas?

void get_packet(char *arg)
{
strcpy(arg, "data");
some_function_t hat_gets_packet (arg);
}


int main()
{
char *array = new char[DESIRED_SIZE];
get_packet(arra y);
cout << array << '\n'; // outputs "data"
}

It's also a good idea to send a second argument as
well: the size of the array, so you can protect
against an overrun.

An alternative to the above is to wrap the array in a
class or struct, and return that. Or store the array
contents in a standard container (e.g. vector) and return
that, and if the caller needs the 'raw' array form, you
can recreate it from the container data.

-Mike

[Kevin Goodsell]

Re: how to return a char array

osmium wrote:
[color=blue]
> Ger writes:
>
>[color=green]
>>I have been trying to return a data packet (as a char array) at the end of[/color]
>
> a
>[color=green]
>>function but that seems to be impossible...
>>I would like to use this char array in a different class..anyone some[/color]
>
> ideas?
>
> Allocate space for the char array, using new, in some function *before*
> calling the 'data packet' function. Pass a pointer to this array around
> until its meaningful lifetime has expired. Then delete it with delete. The
> assignment and deletion do not have to be performed in the same function.
>
>[/color]

Better use new[] and delete[], not new and delete.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

[Bryan Bullard]

Re: how to return a char array


"Ger" <g.inberg@geens pam.student.utw ente.nl> wrote in message
news:bv3hfo$3se $1@ares.cs.utwe nte.nl...

try to avoid using byte arrays to represent strings in c++. std::string is
safer and very flexible.
[color=blue]
> Hi,
>
> I have been trying to return a data packet (as a char array) at the end of[/color]
a[color=blue]
> function but that seems to be impossible...
> I would like to use this char array in a different class..anyone some[/color]
ideas?[color=blue]
>
> greetz,
> Ger
>
>
>
>[/color]

[NKOBAYE027]

Re: how to return a char array

return a reference to a std::vector<cha r> instead - in C++, unless you
absolutely have no choice, you should never use arrays. arrays are evil -
use standard containers instead.

"Ger" <g.inberg@geens pam.student.utw ente.nl> wrote in message
news:bv3hfo$3se $1@ares.cs.utwe nte.nl...[color=blue]
> Hi,
>
> I have been trying to return a data packet (as a char array) at the end of[/color]
a[color=blue]
> function but that seems to be impossible...
> I would like to use this char array in a different class..anyone some[/color]
ideas?[color=blue]
>
> greetz,
> Ger
>
>
>
>[/color]

[Jeff Schwab]

Re: how to return a char array

[color=blue]
> "Ger" <g.inberg@geens pam.student.utw ente.nl> wrote in message
> news:bv3hfo$3se $1@ares.cs.utwe nte.nl...
>[color=green]
>>Hi,
>>
>>I have been trying to return a data packet (as a char array) at the end of
>>a function but that seems to be impossible...
>>I would like to use this char array in a different class..anyone some[/color]
>
> ideas?
>[color=green]
>>greetz,
>>Ger[/color][/color]

NKOBAYE027 wrote:[color=blue]
> return a reference to a std::vector<cha r> instead - in C++, unless you
> absolutely have no choice, you should never use arrays. arrays
> are evil - use standard containers instead.[/color]

1) That's a load of baloney.

2) Returning a reference to a local vector doesn't
solve the problem. The vector will be destroyed
before the caller gets to use it.

3) Please don't top-post.

[Attila Feher]

Re: how to return a char array

Jeff Schwab wrote:[color=blue]
> NKOBAYE027 wrote:[color=green]
> > return a reference to a std::vector<cha r> instead - in C++, unless[/color]
> you > absolutely have no choice, you should never use arrays. arrays[color=green]
> > are evil - use standard containers instead.[/color]
>
> 1) That's a load of baloney.[/color]

Actually the "avoid arrays" is a good advice for beginners. You can do
everything with a vector, and more safely. Of course this is no rule for
production code. :-)
[color=blue]
> 2) Returning a reference to a local vector doesn't
> solve the problem. The vector will be destroyed
> before the caller gets to use it.[/color]

It's fun! :-) (My program works in debug mode, but not in release. Please
help! ;)
[color=blue]
> 3) Please don't top-post.[/color]

Agreed!

--
Attila aka WW

[Jeff Schwab]

Re: how to return a char array

Attila Feher wrote:[color=blue]
> Jeff Schwab wrote:
>[color=green]
>>NKOBAYE027 wrote:[color=darkred]
>> > return a reference to a std::vector<cha r> instead - in C++, unless[/color]
>> you > absolutely have no choice, you should never use arrays. arrays[color=darkred]
>> > are evil - use standard containers instead.[/color]
>>
>>1) That's a load of baloney.[/color]
>
>
> Actually the "avoid arrays" is a good advice for beginners. You can do
> everything with a vector, and more safely. Of course this is no rule for
> production code. :-)[/color]

You're right: Vectors are, indeed, more appropriate as a learning tool
(and for most production purposes). I'm saddened by the "arrays are the
devil" nonsense, though. :(

[color=blue][color=green]
>>2) Returning a reference to a local vector doesn't
>> solve the problem. The vector will be destroyed
>> before the caller gets to use it.[/color]
>
>
> It's fun! :-) (My program works in debug mode, but not in release. Please
> help! ;)[/color]

Livin' on the edge, baby! "I like bungee jumping and volcano luging,
and in my spare time I dereference null..."
[color=blue][color=green]
>>3) Please don't top-post.[/color]
>
>
> Agreed!
>
> --
> Attila aka WW
>
>[/color]

[NKOBAYE027]

Re: how to return a char array

ooops forgive the return of reference faux pas...i was thinking the same as
Nick's answer above - hand in a reference to that vector and then modify the
referenced object within the function. shows that we shouldn't type before
we think...

as to the comment arrays are evil, it's a quote from M. Cline, who sits on
the ANSI C++ standards committee, is his C++ FAQ Lite at
http://www.parashift.com/c++-faq-lite/index.html it's meant to be tongue in
cheek and taken with a grain of salt. :o) Sorry to have offended any former
C programmers.

regards,
Lup
"NKOBAYE027 " <NKOBAYE027@Rog ers.Com> wrote in message
news:5tqRb.2141 7$9Ce1.7832@new s04.bloor.is.ne t.cable.rogers. com...[color=blue]
> return a reference to a std::vector<cha r> instead - in C++, unless you
> absolutely have no choice, you should never use arrays. arrays are evil -
> use standard containers instead.
>
> "Ger" <g.inberg@geens pam.student.utw ente.nl> wrote in message
> news:bv3hfo$3se $1@ares.cs.utwe nte.nl...[color=green]
> > Hi,
> >
> > I have been trying to return a data packet (as a char array) at the end[/color][/color]
of[color=blue]
> a[color=green]
> > function but that seems to be impossible...
> > I would like to use this char array in a different class..anyone some[/color]
> ideas?[color=green]
> >
> > greetz,
> > Ger
> >
> >
> >
> >[/color]
>
>[/color]

[Attila Feher]

Re: how to return a char array

Jeff Schwab wrote:[color=blue][color=green]
>> Actually the "avoid arrays" is a good advice for beginners. You can
>> do everything with a vector, and more safely. Of course this is no
>> rule for production code. :-)[/color]
>
> You're right: Vectors are, indeed, more appropriate as a learning tool
> (and for most production purposes).[/color]

Well, in production they might happily hide errors as well (if you really do
have a small upper limit). But I would say that one is still better off
using the boost array wrapper than "naked" arrays.
[color=blue]
> I'm saddened by the "arrays are the devil" nonsense, though. :([/color]

It is "the teaching". It is easier to scare people away from something (cf.
religions) than teach them to be responsible. ;-)[color=blue][color=green]
>> It's fun! :-) (My program works in debug mode, but not in release.
>> Please help! ;)[/color]
>
> Livin' on the edge, baby! "I like bungee jumping and volcano luging,
> and in my spare time I dereference null..."[/color]

ROFL!

--
Attila aka WW