From: Colin Bartlett <colinb2r@...>
Date: 2010-04-24T23:36:14+09:00
Subject: Re: #object_hexid

On Sat, Apr 24, 2010 at 2:16 PM, Intransition <transfire@gmail.com> wrote:
> Can anyone write a reliable Kernel#object_hexid, a method that returns
> an object's id but in hex, just like Ruby's normal #inspect provides.
> My attempts seems to break depending on the version of Ruby used.
That's something I've wanted when I've been writing #inspect for a class, and
(for aesthetics!) I've wanted the object_id encoding in the default #inspect.
Give that there must (I assume) be a function in the underlying C or
Java (etc) code
to produce the object_id encoding, are there any reasons why that
should not also
be a method in Object?
(The C code for 1.9.1 seems to encode c pointer to the object?)

On Sat, Apr 24, 2010 at 2:22 PM, Dominik Honnef <dominikh@fork-bomb.org> wrote:
> "0x%x" % (object_id << 1)
> should work univerally, I guess.
It seems to work in Ruby 1.8.6 and 1.9.1, but not in JRuby? (See below.)

On Sat, Apr 24, 2010 at 2:31 PM, Brian Candler <b.candler@pobox.com> wrote:
> Is it important that object_hexid returns the same value as reported by
> #inspect, or just some unique id?
I'm not sure (for me, anyway) it's vital that it's the same value as #inspect.
But I've been wondering why (as your code showed) that the hexid in #inspect
is different to #object_id.to_s(16). Can anyone give reasons?
(I've just had a quick look at the code in object.c, and a few other *.c
which included object_id or inspect/to_s, and nothing obvious struck me.
I must confess I found the code not easy to follow, but I only speak pidgin C.)

# code comparing the #inspect encoding of object_id with the object_id
class Q; end
q = Q.new
iid = q.inspect ; iid[-1, 1] = "" ; iid[0, 4] = ""
oid = q.object_id
puts "inspect  #=> " + q.inspect
puts "inspect id #=>   " + iid
puts "oid << 1 #=>     0x" + (oid << 1 ).to_s(16)
puts "Integer(iid) #=> " + Integer(iid).to_s
puts "oid #=>      #=> " + oid.to_s

ruby 1.9.1p243 (2009-07-16 revision 24175) [i386-mingw32]
inspect  #=> #<Q:0x2205b80>
inspect id #=>   0x2205b80
oid << 1 #=>     0x2205b80
Integer(iid) #=> 35675008
oid #=>      #=> 17837504

jruby 1.5.0.RC1 (ruby 1.8.7 patchlevel 249) (2010-04-14 0b08bc7)
  (Java HotSpot(TM) Client VM 1.6.0_14) [x86-java]
inspect  #=> #<Q:0x16fdac>
inspect id #=>   0x16fdac
oid << 1 #=>     0xfb8
Integer(iid) #=> 1506732
oid #=>      #=> 2012