How to convert from ubyte[] to and from float?

[Ali Çehreli via Digitalmars-d-learn]

On 10/18/2014 06:06 PM, Charles Hixson via Digitalmars-d-learn wrote:
> What is the best way to convert from a part of a ubyte[] to a float?
>
> I've tried converting the ubyte[] into a uint, but neither casting the
> uint to a float nor to!float work.
>
> I suppose I could use a "trick record" union, but that seems inelegant.
> If I use pointers, the alignment may (unpredictably) not be proper
> (whatever that means these days).

This is what I understood:

import std.exception;

ubyte[float.sizeof] toBytes(float f)
{
     ubyte* beg = cast(ubyte*)&f;
     return beg[0..f.sizeof];
}

float toFloat(const(ubyte)[] bytes)
{
     enforce(bytes.length >= float.sizeof);
     return *cast(float*)bytes.ptr;
}

void main()
{
     float f = 1.5;

     auto bytes = toBytes(f);
     float f2 = toFloat(bytes);

     assert(f2 == f);
}

There are no alignment issues because f and ubyte[float.sizeof] are not 
related. If you meant that ubyte[] should be a reference to an existing 
float, then toBytes must take by 'ref float' and then it can return a 
ubyte[]. However, it would be the responsibility of the caller to ensure 
that the float would live long enough.

If that happened, then there would be no alignment issues because we 
would have started with a float anyway and the ubyte[] would be 
referring to that float in memory.

Ali