Well, now that you are wise in the way of pointers, please go ahead
and fix the damn page :-)

If something on the wiki doesn't look right, fix it - its a wiki after
all.  (and if your changes aren't right, in theory someone else will
rip your stuff out ... ad infinitum).



On 12 May 2010 08:59, Chuck Remes <cremes.devlist@mac.com> wrote:

> I'll make the modifications for #1 and #2.
>
> The text at the top (#3) was put there by someone else. I just added to the page. It didn't look right to me, but it's been there for a while so I didn't touch it. :)
>
> cr
>
> On May 11, 2010, at 5:33 PM, Wayne Meissner wrote:
>

>> It looks pretty good.
>>
>> A couple of nits:
>>
>> 1) The LibC module can just use:
>>   ffi_lib FFI::Library::LIBC
>>
>> ffi knows that means "whatever the libc on this system is supposed to
>> be", since its a pretty common library people want to map in, and the
>> name differs across platforms (e.g. on linux, its libc.so.6, macos is
>> libc.dylib, windows is msvcrt.dll, aix is something weird, etc.
>>
>> 2) The first arg to MemoryPointer.new can in fact be either a symbol,
>> or anything that responds to #size.
>> e.g.
>>  class S < FFI::Struct
>>    layout :i, :int
>>  end
>>  FFI::MemoryPointer.new(S, 1, false)  # Will allocate space for one
>> instance of S, without clearing the memory first
>>
>> 3) The bit at the top about copying pointers is ... confusing.  A
>> pointer is merely a Fixnum that holds a native memory address, so
>> there is no need to do anything special to "copy" a pointer - just
>> assign it to a like you would any other Fixnum.  Think of "Pointer" as
>> "fixnum with methods to read/write the native memory at the address".
>>
>> The example:
>>
>> b = MemoryPointer.new(:pointer).write_pointer(some_pointer.read_pointer)
>>
>> Doesn't do what you think.  It reads a pointer from the memory
>> pointed-to by some_pointer, allocates a new chunk of memory, and
>> writes that pointer value into that memory - it doesn't copy the value
>> of some_pointer to a new pointer.
>>
>>
>>
>>
>>
>>
>>
>>
>> On 12 May 2010 02:02, Chuck Remes <cremes.devlist@mac.com> wrote:

>>> I just wrote an update to the wiki page on pointers at http://wiki.github.com/ffi/ffi/pointers
>>>
>>> I'd appreciate it if someone more knowledgeable would check it over (the bottom section under the sub-heading) and verify that what I wrote is correct. It seems to be working for me but I've been wrong before! :)
>>>
>>> cr
>>>
>>>

>
>