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I'm currently working with a PLC that supports ANSI C, but uses its own flavour of the GNU compiler, which doesn't compile any variadic functions and things like itoa. So using sprintf & co. isn't an option for converting integers to strings. Can anyone guide me to a site where a robust, sprintf- free implementation of itoa is listed or post a suitable algorithm here? Thanks in advance.

Maxwin
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1 Answers1

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This is from K&R:

void itoa(int n, char s[])
{
    int i, sign;

    if ((sign = n) < 0)  /* record sign */
        n = -n;          /* make n positive */
    i = 0;
    do {       /* generate digits in reverse order */
        s[i++] = n % 10 + '0';   /* get next digit */
    } while ((n /= 10) > 0);     /* delete it */
    if (sign < 0)
        s[i++] = '-';
    s[i] = '\0';
    reverse(s);
}

reverse() just reverses a string.

Alok Singhal
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  • Use this version with care as it can overflow the buffer. – R Samuel Klatchko Jan 26 '10 at 08:39
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    Yes, that's true. The caller has to know if the buffer has enough space or not. Just like `sprintf()`. – Alok Singhal Jan 26 '10 at 08:42
  • Which is why you should never use `sprintf()` and only use `snprintf()` – R Samuel Klatchko Jan 26 '10 at 08:48
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    I agree with you, if you replace "never" with "almost never". In general, one should prefer `snprintf()`. But if one is sure that the target buffer has the required size, `sprintf()` is fine too. See http://stackoverflow.com/questions/1996374/convert-integer-into-an-array/1996500#1996500 for example. – Alok Singhal Jan 26 '10 at 09:14