</p>

<p>
This rule generalizes the previous rule to buffered channels.
It allows a counting semaphore to be modeled by a buffered channel:
the number of items in the channel corresponds to the number of active uses,
the capacity of the channel corresponds to the maximum number of simultaneous uses,
sending an item acquires the semaphore, and receiving an item releases
the semaphore.
This is a common idiom for limiting concurrency.

contains no pointers.
</p>

<p>
There may be one or two arguments to the directives.
If there are two, the first is a bit mask of flags,
which can be written as numeric expressions, added or or-ed together,
or can be set symbolically for easier absorption by a human.
Their values, defined in the standard <code>#include</code>  file <code>textflag.h</code>, are:
</p>

<ul>
<li>