From: "sam.saffron (Sam Saffron)" <sam.saffron@...>
Date: 2013-10-03T10:11:50+09:00
Subject: [ruby-core:57624] [ruby-trunk - Feature #8977] String#frozen that	takes advantage of the deduping


Issue #8977 has been updated by sam.saffron (Sam Saffron).


@hedius

the request is all about exposing:

VALUE
rb_fstring(VALUE str)
{
    st_data_t fstr;
    if (st_lookup(frozen_strings, (st_data_t)str, &fstr)) {
	str = (VALUE)fstr;
    }
    else {
	str = rb_str_new_frozen(str);
	RBASIC(str)->flags |= RSTRING_FSTR;
	st_insert(frozen_strings, str, str);
    }
    return str;
}

the encoding concerns are already handled by st_lookup afaik, as is the gc concern

> def test; x = "asasasa"f; x.object_id; end
> test
=> 70185750124120
> undef :test
> GC.start
> def test; x = "asasasa"f; x.object_id; end
> test
=> 70185736068940

Overall this feature has some parity with Java / .NETs intern, adapted to the world where MRI is not allow you to shift objects around 

@charlie I like #pooled , #dedup feels a bit odd ... I totally understand the concern about #frozen vs #frozen? it can be confusing



----------------------------------------
Feature #8977: String#frozen that takes advantage of the deduping 
https://bugs.ruby-lang.org/issues/8977#change-42238

Author: sam.saffron (Sam Saffron)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: current: 2.1.0


During memory profiling I noticed that a large amount of string duplication is generated from non pre-determined strings.

Take this report for example https://gist.github.com/SamSaffron/6789005 (generated using the memory_profiler gem that works against head) 

">=" x 4953
    /Users/sam/.rbenv/versions/2.1.0-dev/lib/ruby/2.1.0/rubygems/requirement.rb:93 x 4535

This string is most likely extracted from a version. 

Or 

"/Users/sam/.rbenv/versions/2.1.0-dev/lib/ruby/gems" x 5808
    /Users/sam/.rbenv/versions/2.1.0-dev/lib/ruby/gems/2.1.0/gems/activesupport-3.2.12/lib/active_support/dependencies.rb:251 x 3894

A string that can not be pre-determined. 

---- 


It would be nice to have 

"hello,world".split(",")[0].frozen.object_id == "hello"f.object_id 

Adding #frozen will give library builders a way of using the de-duping. It also could be implemented using weak refs in 2.0 and stubbed with a .dup.freeze in 1.9.3 . 

Thoughts ?  





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