检查Clojure（脚本）通道是否已满

Question

Suppose c is a channel of size n . I am trying to write a function in clojure(script) which checks to see if c is full and, if so, closes the channel.

But how does one check to see whether a channel is full?

Answer 1

core.async offers a pair of functions for this:

• offer ! to put something on the channel if space is available, and let you know if it is full.
• poll ! gets something if it's available and lets you know if the channel has nothing to offer at the moment.

So you could write something like:

(if-not (offer! my-chan 42)
   (close! my-chan))

which would accomplish this when you are putting something on the channel. Which is likely safer than trying to have another process watch for the moment that it get's full and then close it. If you really want to just check if it's full you can extract the buffer and ask it:

user> (->> (async/chan (async/buffer 1))
           (.buf)
           (.full?))
false

though think that one through carefully first.