Re: std.digest can't CTFE?

[Stefan Koch via Digitalmars-d]

On Thursday, 31 May 2018 at 21:29:13 UTC, Manu wrote:
"CTFE
Digests do not work in CTFE"

That's an unfortunate limitation... why is, those things? :(

Because CTFE cannot do things which are technically ABI dependent.
You can work around it with code like this:

T fromBytes(T, Endianess endianess = Endianess.LittleEndian) 
(const ubyte[] _data)
pure {
    static assert(is(T : long)); // poor man's isIntegral
    T result;
    static if (endianess == Endianess.LittleEndian) {
        static if (T.sizeof == 4) {
            result = (
                _data[0] |
                (_data[1] << 8) |
                (_data[2] << 16) |
                (_data[3] << 24)
            );
        } else static if (T.sizeof == 8) {
            result = (
                _data[0] |
                (_data[1] << 8) |
                (_data[2] << 16) |
                (_data[3] << 24) |
                (cast(ulong)_data[4] << 32UL) |
                (cast(ulong)_data[5] << 40UL) |
                (cast(ulong)_data[6] << 48UL) |
                (cast(ulong)_data[7] << 56UL)
            );
        } else {
            static assert(0, "only int and long are supported");
        }
    } else {
        static assert(0, "Big Endian currently not supported");
    }

    return result;

}