Encoded hash is not being decoded (rounding bug) about hashids.net

[DwayneBull]

Given that the powers are small ( only as long as the hashed string ) it would be better to use a manual pow function and avoid bigint. To avoid the reliance on System.Numerics and keep existing compatibility.

i.e.

private long Unhash(string input, string alphabet)
 {
    long number = 0;

    for (var i = 0; i < input.Length; i++)
    {
        var pos = alphabet.IndexOf(input[i]);
        number += (long)(pos * Pow(alphabet.Length, input.Length - i - 1));
    }
    return number;
}

private static long Pow(int target, int power)
{
        if (power == 0) return 1;
        long result = target;
        while (power > 1)
        {
            result *= target;
            power--;
        }
        return result;
}

There are a couple of other edge cases in the code that could fail due to floating point math.

[ullmark]

Cool, thanks! I'll have a look and include it in the next version!

[douglasg14b]

@MarkOtter Maybe make a pull request to get the fix in? It doesn't seem like this project has been updated for a few years.

[minhhungit]

@ullmark @douglasg14b hi any news sir

have you had a chance to review this issue @ullmark

[ullmark]

A pull request would have been nice :) I'll update the code and make sure tests execute and then make a release.

[ullmark]

Doesn't seem "System.Numerics" is included in .netstandard 1.0...

[ullmark]

I could apply @MarkOtter code when not using .netstandard1.0. Would that suffice @minhhungit ?

[minhhungit]

I'm still using .net framework so I don't worry much about .netstandard

[MarkOtter]

It seems like System.Numerics is available in Standard 2.0+, or there is a NuGet package for Standard 1.1+.

@ullmark I think the decision should be made what minimum version you'd like to support with this code. Given the implementation support chart, I think going with at least 1.1 is a safe decision.