[squeak-dev] [Vm-dev] [Pharo-dev] Byte & String collection hash performance; a modest proposal for change.
eliot.miranda at gmail.com
Mon May 1 18:55:26 UTC 2017
On Mon, May 1, 2017 at 10:37 AM, Tony Garnock-Jones <tonyg at ccs.neu.edu>
> On 5/1/17 1:26 PM, Levente Uzonyi wrote:
> > I presume that a general purpose in-image solution would be more
> > complex. String already has too many subclasses (6 in Squeak), while at
> > the same time other kind of new subclasses would be welcome too, e.g.
> > Strings with 2-byte characters.
> > Since these properties are orthogonal, there would be many new
> > subclasses to cover all cases.
> A classic motivating case for Traits, right?
Alas no. The problem with String's subclasses is that they're binary
objects. They have no inst vars in which one can cache a hash. They're
juts a flat vector of bytes. If one added a trait to them the system would
fail because there's no way to add an inst var to a binary object in the
current Smalltalk object representation. hence Levente's very clever idea
of hiding the hash in a hidden header word.
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