From: Joel VanderWerf <vjoel@...>
Date: 2009-09-23T08:58:46+09:00
Subject: Re: Getting essid via ioctl

Christoph Kappel wrote:
> Hello.
> 
> To avoid relying on the wireless tools I want to get the essid directly from the device with ioctl, in C 
> this wouldn't be a problem, but in Ruby it's quite different.
> 
> The problem is following struct from wireless.h that is used as input/reply of ioctl:
> 
> struct  iw_point
> {
>   void __user *pointer; /* Pointer to the data  (in user space) */
>   __u16   length;   /* number of fields or size in bytes */
>   __u16   flags;    /* Optional params */
> };
> 
> The pointer part must be a valid address of a memory area, followed by the length in bytes, 
> followed by a flag field. I tried with Array#pack and the bit-struct gem, but haven't found a solution yet.
> 
> Is there a way to bypass this memory pointer problem?

Christoph,

How are you calling ioctl() ? If you're using FFI, then googling for 
FFI::Pointer should help. If you're calling it in some other way and are 
trying to access the binary data in ruby, does the P specifier in 
pack/unpack work?

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407