Change namespace of IO::Buffer to Coolio::Buffer

[Watson1978]

The IO::Buffer class was introduced at Ruby 3.1.
Ref: https://bugs.ruby-lang.org/issues/18020

The cool.io gem has same name class and it has been conflicted. If you used unknowingly, it will overwrite Ruby's IO::Buffer and it might cause problems.

So, this patch will add namespece that it can be used as Coolio::Buffer.

Related to fluent/fluentd#4619

Types of Changes

• Bug fix.

Contribution

• I added tests for my changes.
• I tested my changes locally.
• I agree to the Developer's Certificate of Origin 1.1.

[Watson1978]

@ioquatix Could you please review this PR?

Thanks

[ioquatix]

I'm okay with this, but to avoid the namespace confusion, what do you think about renaming it to Coolio::Buffer.

Using Coolio::IO::Buffer means anyone who writes IO inside module Coolio will now get something different.

Imagine this code:

class MyThing
  include Coolio

  def open
    IO.open(...) # This would now refer to `Coolio::IO`
  end
end

[Watson1978]

@ioquatix Thank you for your review.
I renamed to Coolio::Buffer and moved iobuffer.c into cool.io dir because it has same namespace.

Thanks.

[ioquatix]

This looks great to me, thanks for your effort and implementing the requested changes.

[ioquatix]

I suppose we can make a minor release for this change.

[ioquatix]

I've released v1.9.0 do you mind testing it and letting me know how it is?

[Watson1978]

Thank you!!
OK, I will test cool.io gem v1.9.0 using Fluentd's CI.

If it works as expected, all tests will be successful.
fluent/fluentd#4619