Data.Conduit.TMChan

• Introduction

Contains a simple source and sink for linking together conduits in in different threads. Usage is so easy, it's best explained with an example:

We first create a channel for communication...

 do chan <- atomically $ newTBMChan 16

Then we fork a new thread loading a wackton of pictures into memory. The data (pictures, in this case) will be streamed down the channel to whatever is on the other side.

    _ <- forkIO . runResourceT $ loadTextures lotsOfPictures $$ sinkTBMChan chan

Finally, we connect something to the other end of the channel. In this case, we connect a sink which uploads the textures one by one to the graphics card.

    runResourceT $ sourceTBMChan chan $$ Conduit.mapM_ (liftIO . uploadToGraphicsCard)

By running the two tasks in parallel, we no longer have to wait for one texture to upload to the graphics card before reading the next one from disk. This avoids the common switching of bottlenecks (such as between the disk and graphics memory) that most loading processes seem to love.

Control.Concurrent.STM.TMChan and Control.Concurrent.STM.TBMChan are re-exported for convenience.

• Caveats

It is recommended to use TBMChan as much as possible, and generally avoid TMChan usage. TMChans are unbounded, and if used, the conduit pipeline will no longer use a bounded amount of space. They will essentially leak memory if the writer is faster than the reader.

Therefore, use bounded channels as much as possible, preferably with a high bound so it will be hit infrequently.

Documentation

module Control.Concurrent.STM.TBMChan

sourceTBMChan :: TBMChan a -> Source IO a

A simple wrapper around a TBMChan. As data is pushed into the channel, the source will read it and pass it down the conduit pipeline. When the channel is closed, the source will close also.

If the channel fills up, the pipeline will stall until values are read.

sinkTBMChan :: TBMChan a -> Sink a IO ()

A simple wrapper around a TBMChan. As data is pushed into the sink, it will magically begin to appear in the channel. If the channel is full, the sink will block until space frees up. When the sink is closed, the channel will close too.

module Control.Concurrent.STM.TMChan

sourceTMChan :: TMChan a -> Source IO a

A simple wrapper around a TMChan. As data is pushed into the channel, the source will read it and pass it down the conduit pipeline. When the channel is closed, the source will close also.

sinkTMChan :: TMChan a -> Sink a IO ()

A simple wrapper around a TMChan. As data is pushed into this sink, it will magically begin to appear in the channel. When the sink is closed, the channel will close too.