From: Takaaki Tateishi <ttate@...>
Date: 2004-07-19T00:16:25+09:00
Subject: Re: ext/dl problem with unsigned char*


Randy Lawrence said:
> 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*".

Basically pointer types are treated as 'void*', but 'char*' is treated
as string. So 'unsigned char *' is the pointer type and a string given
as a parameter in ruby layer is automatically converted to a pointer
object to a copy of the given string. I think your C function modified
a copy of a string.

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

I recommend you to use String#to_ptr as follows, if you specify 'unsigned
char *'.

inOutPtr = inOut.to_ptr
inOutLen = inOut.length
result = FooLib.foo(inOutPtr, inOutLen)
inOut = inOutPtr.to_s(inOutLen)
...
-- 
Takaaki Tateishi <ttate@ttsky.net>