LiveCode Builder: Passing buffer to foreign handler

[Peter TB Brett]

On 17/04/2016 16:14, Dar Scott wrote:
> I'm using LiveCode 8.0.0 RC 1 on the Mac.  I'm tinkering with LiveCode Builder to make library extensions.
>
> I want to pass a buffer pointer to a foreign handler, in a hardware vendor supplied dynamic library  Then I want to access the bytes/words in that buffer.
>
> What's the best way to do this?
>
> I thought about building up a value of type data of the right length.  Is the data value contiguous?  Does it stay in one place?  Is the value allowed to change?  I think breaking equality is OK.  How do I get the pointer to the underlying first byte?  (MCDataGetBytePtr()?)  Or is a data ref automatically converted to pointer as needed?
>
> Or do I need to allocate my own memory?  Are any <builtin> functions are available to do this?  How do I get to the bytes after I make the call to the foreign function?  (MCMemoryAllocate()?)

If you want a particularly horrible example, check out my wrapper for 
the poll(2) system call:

https://github.com/peter-b/undergrowth/blob/master/_poll.lcb

I won't claim it's the "best way to do this" but it appears to mostly work!

> Is this noise on this list?  Should this question be elsewhere?

No, it's completely on-topic.

                                    Peter

-- 
Dr Peter Brett <peter.brett at livecode.com>
LiveCode Open Source Team

LiveCode 2016 Conference: https://livecode.com/edinburgh-2016/