Display in base-10?

bignum_to_string appears to render a struct bn as hex rather than decimal; can we get a decimal option?

[as-iotex]

@kokke How difficult would it be to implement printing as decimal? I am also interested in this functionality.
I am not 100% sure on how to do it but I would not mind giving it a try. Does the method indicated below look correct?
https://stackoverflow.com/questions/8023414/how-to-convert-a-128-bit-integer-to-a-decimal-ascii-string-in-c

[Ev1lT3rm1nal]

@kokke any update or plan for implementation? or it wil be discarded

[keithmo]

You can roll your own.

In bn.h, add:

void bignum_to_base10(struct bn *n, char *str, int nbytes);

In bn.c, add:

void bignum_to_base10(struct bn *n, char *str, int nbytes) {
    require(n, "n is null");
    require(str, "str is null");
    require(nbytes > 0, "nbytes must be positive");

    struct bn const10;
    struct bn current;
    struct bn quotient;
    struct bn remainder;
    char *scan = str;
    char *end = str + nbytes;

    bignum_from_int(&const10, 10);
    bignum_assign(&current, n);

    // This puts the digits into the buffer in reverse order
    // (starting with the least significant digit).

    while (scan < end) {
        bignum_divmod(&current, &const10, &quotient, &remainder);
        *scan++ = '0' + remainder.array[0];

        if (bignum_is_zero(&quotient)) {
            break;
        }

        bignum_assign(&current, &quotient);
    }

    require(scan < end, "str is too small");

    *scan-- = '\0';

    // Reverse the digits.

    while (str < scan) {
        char tmp = *str;

        *str++ = *scan;
        *scan-- = tmp;
    }
}

Notes:

• I'm planning to use this library in a personal project.

• I haven't actively written C in about 25 years, so please review carefully (especially for memory issues).

• There are likely more performant ways to do this.

• @kokke: Feel free to incorporate this into this library if you want.