From: Randy Lawrence <jm@...>
Date: 2004-07-17T15:53:34+09:00
Subject: ext/dl problem with unsigned char*

Hi,

The string I pass to a c function does not appear to get modified if I 
use "unsigned char*" in ruby instead of plain "char*".

Question 1: Is it wrong to pass a string object as a parameter which 
might contain non-ascii values when the c function returns?

Qustion 2: The before and after values of 'inOut' remains the same 
unless the parameter type in line 4 is changed from "unsigned char*" to 
"char*".  What can I do to fix this without resorting to Base64 encoding?

module FooLib
   extend DL::Importable
   dlload './foolib.so.0'
   extern "int foo(unsigned char*, unsigned int)" #this line
end

inOut = 'original data'
puts "before: #{inOut}"
result = FooLib.foo(inOut, inOut.length)
puts "after: #{inOut}"