Re: [boost] [endian] Use in Hash algorithms

Subject: Re: [boost] [endian] Use in Hash algorithms
From: Scott McMurray (me22.ca+boost_at_[hidden])
Date: 2010-05-29 10:02:45

On 29 May 2010 00:05, Terry Golubiewski <tjgolubi_at_[hidden]> wrote:
> What is Magic<int, int>?
>

Something that needs implementing as a test of an endian library.

For example, I could implement it with what I wrote as follows:

    template <int In, int Out>
    struct Magic {
        array< uint_t<In>::least, Out/In > in;
        unsigned i;
        Magic() : i() {}
        void put(uint_t<In>::least x) { in[i++] = x; }
        uint_t<Out>::least get() const {
            array<uint_t<Out>::least, 1> out;
            pack<big_bit, In, Out>(in, out);
            return out[1];
        }
    };

With Beman's it would be something like this:

    template <int In, int Out>
    struct Magic {
        union {
            array< endian<big, uint_t<In>::exact>, Out/In> in;
            endian<big, uint_t<Out>::exact> out;
        };
        array< uint_t<In>::least, Out/In > in;
        unsigned i;
        Magic() : i() {}
        void put(uint_t<In>::least x) { in[i++] = x; }
        uint_t<Out>::least get() const {
            return out;
        }
    };

I think, anyways, though it requires C++0x unions.

That, of course, can't handle Ins or Outs that are not multiples of CHAR_BIT.