[Development] QStringRef conversion functions

[André Pönitz]

On Wed, Jun 13, 2012 at 08:36:52PM +0200, Thiago Macieira wrote:
> On quarta-feira, 13 de junho de 2012 18.14.59, aaron.kennedy at nokia.com
> wrote:
> > Won't a QString always require an allocation for the d-ptr?  So
> > it'll never be quite as cheap as QStringRef.
> 
> Not exactly.
> 
> A QStringRef points to an existing QString. Therefore, if we take a
> QString that is pointing to a substring of an existing QString, the
> d-ptr is already allocated. The new QString would be as cheap as the
> current QStringRef.
> 
> The issue we'll run into is that a substring could be "holding
> hostage" a huge chunk of memory.

This is not much different from current usage. The difference would
be the "outer" string contents being re-allocated as result of
non-const operations on it. This "works" (to a certain degree...)
with QStringRef, but wouldn't with "cheap substrings".

However, I still have to see such a "mutable" case in practice.
The QStringRef uses I am aware of are very limited in scope,
often just saving a single copy of (parts of) the owning strings.
Nice, but not even close to the potential of "cheap substrings".

Andre'