C interface provides a pointer and a length... wrap without copying?

[cy via Digitalmars-d-learn]

So a lovely C library does its own opaque allocation, and 
provides access to the malloc'd memory, and that memory's length. 
Instead of copying the results into garbage collected memory 
(which would probably be smart) I was thinking about creating a 
structure like:

struct WrappedString {
   byte* ptr;
   size_t length;
}

And then implementing opIndex for it, and opEquals for all the 
different string types, and conversions to those types, and then 
it occurred to me that this sounds like a lot of work. Has 
anybody done this already? Made a pointer/length pair, that acts 
like a string?