A little help with importing c library

Ruby
1

Hello,

I am very new to Ruby, but I am giving it a try. If I am able to load
the dll and call its functions, I will go into more detail. The .dll is
created in VS2005 on XP os

First of all, I used the search function of the forum, but I didn’t find
what I was looking for.
After initial problems, my ruby script recognizes the library (if I
remove the file, it complains).

It’s a C wrapper library for a C++ library that has just a few functions
for now.

I am stuck at the beginning :slight_smile:
My library is called qfinterface.dll and I would like to call the
function CreateSession(const char *) that returns an int, and pass it a
string.

I mostly get the error “uninitialized constant” when trying to call the
function, and I’ve tried so many different things, that I am losing
track of what I tried and what not. right now I get “undefined local
variable or method”

this is my script sofar(in one of its versions):

require ‘qfinterface’

puts “hello”

Qf = qfinterface.CreateSession(“hd”)

def main()

puts “hello”

 #QfInterface.CreateSession("sf")

end

main()

would you please point me into right direction in how to call these
classes.

please let me know if you need further information.

Thanks for your help!

2

I got it!!

in case another lost soul needs it, here is how:

require ‘qfinterface’
require ‘Win32API’

puts “hello”

CreateSession = Win32API.new(“qfinterface”,“CreateSession”,[“P”],“I”)

def main()

 puts "hello"
 check = CreateSession.call("mystring")

end

main()

3

On Feb 27, 2007, at 6:24 PM, Tea Figuric wrote:

I mostly get the error “uninitialized constant” when trying to call
the
function, and I’ve tried so many different things, that I am losing
track of what I tried and what not. right now I get “undefined local
variable or method”

I’m assuming you’ve read README.ext already?
http://svn.ruby-lang.org/cgi-bin/viewvc.cgi/branches/RUBY/README.EXT?
view=markup

Have you investigated using the inline library? It might make more
sense if you just need a few functions.

Using C from Ruby is a bit more complex than just regular ruby
programming, but hopefully those links can get you started.
-Mat

4

Mat S. wrote:

On Feb 27, 2007, at 6:24 PM, Tea Figuric wrote:

I’m assuming you’ve read README.ext already?
http://svn.ruby-lang.org/cgi-bin/viewvc.cgi/branches/RUBY/README.EXT?
view=markup

Have you investigated using the inline library? It might make more
sense if you just need a few functions.
rubyinline | software projects | by ryan davis

Using C from Ruby is a bit more complex than just regular ruby
programming, but hopefully those links can get you started.
-Mat

Thank you for your response Mat, I will look into the links.

The library should be used by different scripting languages and
languages, so it should be as generic as possible.

In the meantime, I ran into a different problem, and I am having
problems finding an answer to it.

Since my C/C++ functions return only int, I have a function to which I
pass a buffer (as char), and befferLength (as int), where the buffer
should be populated inside of the function, and I have access to the
value from the outside. something like int (or void) GetValue(char
*buffer, int bufferLength);

How do I pass a char* from ruby? is there something to convert from
string to char * without having to change my C lib?

Thanks again for your help!