os-k/kaleid/libc/itoa.c

//----------------------------------------------------------------------------//
//                                OS on Kaleid                                //
//                                                                            //
//  Authors:    spectral`                                                     //
//              NeoX                                                          //
//                                                                            //
//  Desc:       Conversion utilities - itoa family                            //
//----------------------------------------------------------------------------//

#include <libc.h>

// Digits table for bases <=36 (unused)
#if 0
static const char digits[] =
        "0123456789abcdefghijklmnopqrstuvwxyz";
#endif

//
// Integer to string in any base between 2 and 36 (included)
// Returns str
//
#if defined(_NEED_ITOA)

#define _IL_MIN INT_MIN
#define _IL_MIN_STRING "-2147483648"
char *itoa(int i, char *str, int base)
{
    int rem;

#elif defined(_NEED_LTOA)

#define _IL_MIN LONG_MIN
#define _IL_MIN_STRING "-9223372036854775808"
char *ltoa(long i, char *str, int base)
{
    long rem;

#elif defined(_NEED_UTOA)

char *utoa(uint i, char *str, int base)
{
    uint rem;

#elif defined(_NEED_ULTOA)

char *ultoa(ulong i, char *str, int base)
{
    ulong rem;

#else
#error "What am I supposed to declare?"
#endif
    char *orig = str;

#if defined(_NEED_ITOA) || defined(_NEED_LTOA)
    // Deal with negatives
    int neg = 0;
    if (i < 0 && base == 10) {

        // Handle INT_MIN and LONG_MIN...
        if (__builtin_expect(i == _IL_MIN, 0)) {
            strcpy(orig, _IL_MIN_STRING);
            goto leave;
        }

        else {
            neg = 1;
            i = -i;
        }
    }
#endif

    // Only handle base 2 -> 36
    if (base < 2 || base > 36) {
        seterrno(EINVAL);
        *orig = '\0';
        goto leave;
    }

    // Deal with zero separately
    if (i == 0) {
        *str++ = '0';
        *str = '\0';
        goto leave;
    }

    // Compute digits... in reverse order
    while (i > 0) {
        rem = i % base;
        *str++ = (rem > 9)
               ? (rem - 10) + 'a'
               :  rem       + '0';
        i /= base;
    }

#if defined(_NEED_ITOA) || defined(_NEED_LTOA)
    if (neg) *str++ = '-';
#endif

    *str = '\0';

    // Reverse the string
    orig = strrev2(orig);

    // End of conversion
leave:
    return orig;
}