Hi. Been there ... done some of it.
I use DL quite often on HPUX to invoke Cobol/C  modules from libraries.
The best rule I can offer is that before passing any structured parameter,
you should 'pack' it to the
form that the target program expects.
Ruby will just pass a pointer to the packed string, and the target program
can interpret it however the hell it wants.
eg.,
a=[3,"a1","a2","a3"]
param=a.pack("LA5A5A5") # (integer + 3x5byte array of strings) => 19 byte
string
result=routine[param].first

hth,
Tad


I located an old test script which may be of some help :
The script calls a Cobol module called FCREFNUM from a shared library
The routine expects 3 parameters passed by reference, the 3rd parameter is
a simple array.

require "dl"
ctrargs=%w{0 1 999999}
ctrname=ARGV[0].upcase     if ARGV.size >=1
ctrargs=ARGV[1].split(":") if ARGV.size >=2
Image3k =DL.dlopen("/home/acore_dev/library/lib/libimage3k.sl")
fcrefnum=Image3k["FCREFNUM","ISSS"]
counterstart=ctrargs[0].rjust(10,"0") # 10 digit zero
counterincr =ctrargs[1].rjust(10,"0") # 10 digit zero
counterend  =ctrargs[2].rjust(10,"0") # 10 digit zero
counterparms=[counterstart,counterincr,counterend].pack("a10a10a10")
countervalue="0".rjust(10,"0")
countername=ctrname.ljust(8)

n=fcrefnum[countername,countervalue,counterparms].first # call FCREFNUM

p [countervalue,n]



                                                                           
           Internet                                                        
           blackapache512                                                  
           -ticket@yahoo.                                             Pour 
           com                    ruby-core / ruby-lang.org                  
                                                                        cc 
           04/05/2009                                                      
           07:44                                                     Objet 
                                  [ruby-core:23354] Ruby/DL Documentation  
                                                                           
              Veuillez                                                     
             rñÑondre                                                20
           ruby-core@ruby                                                  
             -lang.org                                                     
                                                                           
                                                                           




Hello,

recently i have been trying to learn and use dl library. while searching i
found this excellent link
http://www.jbrowse.com/text/rdl_en.html

unfortunately it is specific to 1.8.x

i wonder how people here use DL, since it is very scarcely documented. i
have been trying to
hack around ./ext/dl/*.c files but i have gained very little usable
information.

ok, my question is about passing an array from ruby to some native
libraries (IPP(http://software.intel.com/en-us/intel-ipp/) to be specific)
on windows. yes i about other alternatives, i could embed ruby in my app
and do whatever, there is gr8 support there
but this is about quickly loading and using native libraries via dynamic
loader.

consider code below
some_fast_math_function( float* array, int len);

then how to pass 'array' argument from ruby ?
i tried this

require 'dl'

module NativeLibs
# do the job for accessing some_fast_math_function
end

array = DL.malloc(size)
NativeLibs.some_fast_math_function( array, size) # crashes :(

some how sucess is elusive for me, this crashes(core dumps) for me, i am
sure this is due to my inexperienced stunts with DL

Aston



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