Re: Algorithm help: passing strings between threads with minimal copying

[Ross Bencina <rossb-lists@...>]

Hi Rena,

> I wondered if anyone else had any feedback on this.

I like using atomic reference counting for this kind of thing.

Assuming that the string buffers are immutable, here's an idea:

Arrange for your allocator to allocate these string buffers specially. 
Lua state A will still think that they are normal memory blocks, but 
under the hood you will have made room for an extra reference count 
that's modified using atomic increment/decrement.

State A gets a 1 count to the buffer when it allocates the block. That 
will be decremented when the GC frees the memory.

When you send the string to State B, increment the count. When you've 
finished with the buffer in state B, decrement the count. When the count 
drops to zero (in whichever thread), free the buffer.

Make sure you use an appropriate library/api for doing the atomic inc/decs.

Ross.