toString refactor in druntime

[Kagamin via Digitalmars-d]

On Thursday, 30 October 2014 at 15:32:30 UTC, Steven 
Schveighoffer wrote:
> This would require sink to write the buffer before it's first 
> call, since you don't track that.

That's delegated to the sink delegate.

> Wouldn't it be better to track the "used" length in buff 
> directly so write can handle that?

The used length is tracked by shrinking the buff. This only shows 
the callee's perspective.