As well as the jack ring buffer, I've looked at several others now, and their example code. The most significant thing that seems to be different about them (from a usage point of view) is the way they handle overflows. However, if the buffer size is defined as an exact multiple of the data type/structure and only complete structures are pushed or popped, would I be right in thinking that you would only need to check on an all/none basis? Have I missed something that could cause a partial data transfer? -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song.