cast safe

[grahamo]

Doh,

In my last mail I meant the function atoi instead of sprintf... and I
also meant to use an int instead of an unsigned int.........

this is the approach I mean , ignore the other email...sorry :(


unsigned char* data = foo();
int result = atoi((char*)dat a)


Is that correct? Assuming new c++ style casts are used, is the above
right or completely erroneous.


Cheers

Graham


From: graham_walsh50@ hotmail.com (grahamo)
Newsgroups: comp.lang.c++
Subject: cast safe

NNTP-Posting-Host: 194.206.100.24
Message-ID: <79528aa8.04121 40618.fe964cc@p osting.google.c om>

Hi,

i know I should use the new style casts and I intend to however I
would like to know how I go about this;

I have an unsigned char* that a 3rd party API returned to me. The API
reads text from a file and gives me that test as an unsigned char*.
For the sake of this example the text string is "100"

unsigned char* data = foo();

I need to get this into an unsigned int, which is what it ultimately
should be however I'm not sure of the best approach. I can cast it to
a char* and then use sprintf(result, "%d", arg) but I'm not sure if
thats the best approach.

What's the *correct* way to achieve it... in terms of code correctness
and "correct approach".

Thanks much for any info (as usual:)

GrahamO

[Victor Bazarov]

Re: cast safe

grahamo wrote:[color=blue]
> [...]
> this is the approach I mean , ignore the other email...sorry :(
>
>
> unsigned char* data = foo();
> int result = atoi((char*)dat a)
>
>
> Is that correct? Assuming new c++ style casts are used, is the above
> right or completely erroneous.[/color]

It's commonly used, but it's not the best way, and often is unacceptable.
'atoi' has no way to report an error. You always get 0 whether it really
was "0" or it was something that couldn't be converted. Use 'strtol'.
[color=blue]
> [...][/color]