[RCR]: Replacing IO.select with predicates

[Bill Atkins]

When you have to use IO.select, code can get kind of ugly. Consider
the following code, which determines which connections in the @conns
array are writeable, readable, or have errors. It then calls the
process method, passing in the flags for read, write, error.

def tick
rconns, wconns, econns = select @conns, @conns, @conns, @timeout

@conns.each do |conn|
read = rconns.include? conn
write = wconns.include? conn
error = econns.include? conn

process conn, read, write, error
end
end

def process conn, read, write, error
if read
...
end

if write
...
end

if error
...
end
end

This code doesn't seem too neat to me, so I overrode part of IO to
support the use of predicates. Now one can do:

def tick
@conns.each do |conn|
process conn
end
end

def process conn
if conn.readable?
...
end

if conn.writable?
...
end

if conn.error?
...
end
end

To me, this code is a lot neater. The implementation is below:

class IO
attr_accessor oll_timeout

def readable?
res = IO.select [self], nil, nil, @poll_timeout || 0.01
res and not res[0].nil?
end

def writable?
res = IO.select nil, [self], nil, @poll_timeout || 0.01
res and not res[1].nil?
end

def error?
res = IO.select nil, nil, [self], @poll_timeout || 0.01
res and not res[3].nil?
end
end

If people here like this, I'll submit it to rcrchive. Any thoughts?

Bill