Re: Pooling of strings is good

[Coroutines <coroutines@...>]

On Fri, Aug 22, 2014 at 3:59 AM, Jay Carlson <nop@nop.com> wrote:
> Mutable strings are...a folly of a quaint, bygone era. They are warts on
> otherwise timeless designs like Scheme and Smalltalk.
>
> Get a mutable octet-vector object type. You'll be much happier.

Again I get this feeling like people love to speak in generalizations
on this list :\  Perhaps you know this: In networking/socket stuff
it's useful to reuse a buffer if you know you're receiving frames of a
fixed size, packets of a fixed size -- it can be wasteful and
contentious to allocate for strings to push this data into.  I work
with other libraries that expect strings -- this received data isn't
compared against it is parsed (so pointer comparisons are not a huge
gain for pooled strings).  This data is almost always unique because
of things like the IP header making it so.  Userdata on its own is
pretty inaccessible -- you cannot make comparisons between userdata or
use the functions provided by the string library to parse userdata
directly.  Strings are a thin abstraction over userdata -- it feels
like I'm working around an API that should be more accomodating.  If I
wanted to minimally change Lua how it is now, I'd make it so userdata
can be used in the same places strings can.

Essentially:
immutable_string1 == immutable_string2 -- would be a pointer comparison
immutable_string1 == mutable_string3 -- would be a memcmp()

I'm somewhat surprised people doing embedded work don't wish userdata
could conform to being a mutable string type in OOM situations.
Modifying a string does mean allocating for it twice..