From: Robert Klemme <shortcutter@...>
Date: 2006-05-02T02:18:57+09:00
Subject: Re: Shortcut for [string].pack("p*").unpack("l").first ?

2006/5/1, Berger, Daniel <Daniel.Berger@qwest.com>:
> > What do you want with a memory address in Ruby-land?  If
> > you're in an extension then there's probably an easier way to
> > get at the address.
>
> Short answer: Win32API

Here you got me convinced.

> strcmp1 = Win32API.new('msvcrt', 'strcmp', 'PP', 'I')
> strcmp2 = Win32API.new('msvcrt', 'strcmp', 'LL', 'I')
>
> str1 = "hello"
> str2 = "hello"
> str3 = "world"
>
> addr1 = [str1].pack("p*").unpack("l").first
> addr2 = [str2].pack("p*").unpack("l").first
> addr3 = [str3].pack("p*").unpack("l").first
>
> # Using strings
> strcmp1.call(str1, str2) # 0
> strcmp1.call(str1, str3) # -1
>
> # Using string addresses
> strcmp2.call(addr1, addr2) # 0
> strcmp2.call(addr1, addr3) # -1

Now you lost me again: if you can use a string as well as a pointer
then why bother to use the pointer? Are there places where you cannot
do that?

> I suppose I could stop whining and just extend the String class. :)

That's definitively an option. :-))

> class String
>    def ptr
>       [self].pack("p*").unpack("l").first
>    end
> end

Just a thought: does it make sense to raise an exception or print a
warning if the string is not frozen?  Otherwise the address could
point into limbo...

Cheers

robert

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