Shortcut for [string].pack("p*").unpack("l").first?

ruby-talk
1

Short answer: Win32API

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

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

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

This might be useful for Ruby/DL as well.

Regards,

Dan

PS - Many thanks to Heesob for teaching me some of these things lately.
:slight_smile:

This communication is the property of Qwest and may contain confidential or
privileged information. Unauthorized use of this communication is strictly
prohibited and may be unlawful. If you have received this communication
in error, please immediately notify the sender by reply e-mail and destroy
all copies of the communication and any attachments.

···

-----Original Message-----
From: Robert Klemme [mailto:shortcutter@googlemail.com]
Sent: Monday, May 01, 2006 10:53 AM
To: ruby-talk ML
Subject: Re: Shortcut for [string].pack("p*").unpack("l").first ?

2006/5/1, Berger, Daniel <Daniel.Berger@qwest.com>:
> Hi all,
>
> If I want to get the underlying pointer address of a
> Ruby string, I can do this:

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.

2

> 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. :slight_smile:

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

···

2006/5/1, Berger, Daniel <Daniel.Berger@qwest.com>:

--
Have a look: Robert K. | Flickr