NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part2/10148

Text File | 1996-08-05 | 2.0 KB | 68 lines

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From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c
Subject: Re: Determining the length of an int in string form
Date: Fri, 15 Mar 96 16:21:16 GMT
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In article <[e-mail]>
           [e-mail] "Steve Fogoros" writes:

>Dave Payne wrote:
>>
>> Consider this:
>>
>> I have a variable of type int, and I would like to use the sprintf()
>> function to write this variable to a string.  However, I want to
>> dynamically allocate the space for the string, and only malloc enough
>> space to hold the int.  Here's a code fragment that may illustrate this
>> more clearly:
>>
>
>Here is what I would do,
>
> char buf[80]; // int could be any length when converted. (Twenty years from
> now
>               //    will int be 256 bits? That would be over 80 digits.)
>               // In the mean time you should make buf at least buf[12] because
>               //    int could be 32 bits. For 64 bit use buf[22];

If you are writng C code you can't use // - it is a syntax error.

There is no need to make buf an external declaration - it can be a local
variable in func1().

You can calculate a suitable size for buf e.g.

#include <limits.h>

#define INTBUF_SIZE    (sizeof(int) * CHAR_BIT / 3 + 2)

> void func1()  {
>
>   int    i = 1234;
>   char  *a;
>
>   sprintf(buf,"%s%d","The value of i is ",i);

And with the reduced buffer size we'd better make that:

    sprintf(buf,"%d",i);

>   a = malloc(strlen(buf + 1));

Don't forget that sprintf returns the length of the string it writes, unless
your system library is prehistoric.

--
-----------------------------------------
Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
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