sprintf confusion

[arnuld]

For my program , I want to convert an integer into array of characters. I
see C has an atoi function o convert from an array of characters to
integers but no standard function to convert from integer to an array opf
chars. Why so ? Does that conversion not come into practice ?


we have sprintf but that riddles with the buffer-overflow problem :( and
snprintf is not in ANSI but in C99.


I have a network program in C ( which is not topical here, hence I did
not post the code). The client sends a number to the server and server
squares the number and sends it back to the client. Now any communication
between them happens using characters. So client sends an array of
characters to the server:

arr[] = { '3', '\0' };


and the server reads and square the number and sends this array back to
the client:

arr_new[] = { '9', '\0' };


Right now I solved the problem using sprintf and by using the number whose
squares are of one digit and I have also limited the size of array to 2
only.

but is this the C way of doing things ?




--

http://lispmachine.wordpress.com/

my email ID is @ the above blog.
just check the "About Myself" page :)

[Bart]

Re: sprintf confusion

On May 15, 6:21 pm, arnuld <sunr...@see.si gs.invalidwrote :

For my program , I want to convert an integer into array of characters. I
see C has an atoi  function o convert from an array of characters to
integers but no standard function to convert from integer to an array opf
chars. Why so ?  Does that conversion not come into practice ?
>
we have sprintf but that riddles with the buffer-overflow problem :( and
snprintf is not in ANSI but in C99.

I have itoa() and ltoa() on my C system. But I suspect these may not
be standard [why not?].

Then sprintf seems a good alternative. Just give it a big enough
buffer size (certainly more than 2 characters!). After all how big can
an integer be? Give it 100 characters and be done with it.

Or use it to create your own itoa().

--
Bartc

[pete]

Re: sprintf confusion

Bart wrote:

On May 15, 6:21 pm, arnuld <sunr...@see.si gs.invalidwrote :

>For my program , I want to convert an integer into array of characters. I
>see C has an atoi function o convert from an array of characters to
>integers but no standard function to convert from integer to an array opf
>chars. Why so ? Does that conversion not come into practice ?
>>
>we have sprintf but that riddles with the buffer-overflow problem :( and
>snprintf is not in ANSI but in C99.

>
I have itoa() and ltoa() on my C system. But I suspect these may not
be standard [why not?].
>
Then sprintf seems a good alternative. Just give it a big enough
buffer size (certainly more than 2 characters!). After all how big can
an integer be? Give it 100 characters and be done with it.
>

I'm familiar with itoa
as a code example and an exercise from K&R, sec 3.6.
You still need a buffer with that.

--
pete

[Richard Heathfield]

Re: sprintf confusion

Bart said:

<snip>

After all how big can an integer be?

You can find out with sizeof.

If you want a buffer big enough to support an integer parameter n, you can
get one like this (given appropriate furniture, e.g. <limits.h>) - the
#defines are merely for explanatory purposes and I don't propose that you
use them in Real Code:

#define BYTES_PER_INT (sizeof n)
#define BITS_PER_BYTE (CHAR_BIT)
#define BITS_PER_INT (BYTES_PER_INT * BITS_PER_BYTE)
#define BIT_CAPACITY 3 /* see below */
#define ALLOW_FOR_MINUS 1
#define ALLOW_FOR_TERM 1
#define DIGIT_COUNT ((BITS_PER_INT + BIT_CAPACITY - 1) / BIT_CAPACITY)

#define BUFFER_SIZE (ALLOW_FOR_MINU S + DIGIT_COUNT + ALLOW_FOR_TERM)

Bit capacity: since decimal representation gives us ten digits ('0' through
'9'), each digit can represent log(2)10 = 3.32+ bits, so it can certainly
represent 3 bits.

Note that for decimal representation the calculated buffer size is always
sufficient, but it can err a little - always on the generous side.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Mark McIntyre]

Re: sprintf confusion

arnuld wrote:

For my program , I want to convert an integer into array of characters. I
see C has an atoi function o convert from an array of characters to
integers but no standard function to convert from integer to an array opf
chars. Why so ? Does that conversion not come into practice ?

Its commonplace to need to read input and convert it to numbers, but the
reverse is less common.

we have sprintf but that riddles with the buffer-overflow problem :( and
snprintf is not in ANSI but in C99.

sprintf() can be used effectively if you're careful.

Right now I solved the problem using sprintf and by using the number whose
squares are of one digit and I have also limited the size of array to 2
only.
>
but is this the C way of doing things ?

yes.

--
Mark McIntyre

CLC FAQ <http://c-faq.com/>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >