I am having some trouble working with this library. Conversion from int seems to break down for large numbers, even when the number is within the JS safe range.

Take a look at the following code: https://ellie-app.com/mMqXP4NnLsNa1
The value given to all of those operations is lower than MAX_SAFE_INTEGER, but the result is still not what was put in when going back to string through Int64.

The documentation for Int64.fromInt says it is guaranteed to work for integers in the safe JS range. Yet, this is not the behavior I'm seeing.

Or maybe toSignedString and/or toUnsignedString are broken? I don't know.

Tests use Fuzz.intRange 0 0xFFFFFFFF but maximum allowed value for Fuzz.intRange is 0x7FFFFFFF.

Int64.fromInt32s 4 18 |> Int64.toHex -- "0000000400000012"

Int64.fromInt32s 4 18 |> Int64.shiftLeftBy 0 |> Int64.toHex -- "0000001600000012"

Int64.rotateLeftBy 0 does behave as expected though.

(thanks for the package though - will be useful to me once bugs ironed out)

I'm currently trying to add int64 encoders and decoders to elm-protocol-buffers
and I'm struggling to implement the VarInt encoding.
The int32 version currently converts the number to base 128, right shifts and continues in a loop.

This is the code:

toVarIntEncoders : Int -> List Encode.Encoder
toVarIntEncoders value =
    let
        base128 =
            Bitwise.and 0x7F value

        higherBits =
            Bitwise.shiftRightZfBy 7 value
    in
    if higherBits /= 0x00 then
        Encode.unsignedInt8 (Bitwise.or 0x80 base128) :: toVarIntEncoders higherBits

    else
        [ Encode.unsignedInt8 base128 ]

I cannot do this with Int64, since the inner values are not exposed.
Using Int64.encode instead of Encode.unsignedInt8 has the correct first two bytes but too many zeros afterwards.

Here is an example:

> minusOne = Int64.fromInt32s 0 -1
Int64 0 4294967295 : Int64.Int64
> xored = Int64.xor (Int64.fromInt 0) minusOne
Int64 0 -1 : Int64.Int64

The issue is that other operations do not work as expected anymore - comparing does not return EQ and == returns False.