block file reads and lazy utf-8 decoding

[Jon D via Digitalmars-d-learn]

On Thursday, 10 December 2015 at 00:36:27 UTC, Jon D wrote:
> Question I have is if there is a better way to do this. For 
> example, a different way to construct the lazy 
> 'decodeUTF8Range' rather than writing it out in this fashion.

A further thought - The decodeUTF8Range function is basically 
constructing a lazy wrapper range around decodeFront, which is 
effectively combining a 'front' and 'popFront' operation. So 
perhaps a generic way to compose a wrapper for such functions.

>
> auto decodeUTF8Range(Range)(Range charSource)
>     if (isInputRange!Range && is(Unqual!(ElementType!Range) == 
> char))
> {
>     static struct Result
>     {
>         private Range source;
>         private dchar next;
>
>         bool empty = false;
>         dchar front() @property { return next; }
>         void popFront() {
>             if (source.empty) {
>                 empty = true;
>                 next = dchar.init;
>             } else {
>                 next = source.decodeFront;
>             }
>         }
>     }
>     auto r = Result(charSource);
>     r.popFront;
>     return r;
> }