Implement prototype of flexible hook handler class

[syucream]

#36

• Separate logic related to thread shared/local data.
• Add a new class, load handler and insert appropriate hook plugins.
• Refactoring.

- [ ] Modify unit test code will be fixed by #75

[coveralls]

Coverage decreased (-51.7%) to 0.0% when pulling bf60a27 on feature/hook_prototype into f4b525a on master.

[syucream]

Idea notes

Requirements

• low memory consumption
• safely memory access

Idea

• Enforce users to create their handler class(or module?). For example:

module MyEventHandler
  def on_send_request_hdr
    ...
  end
end

• Generate new obj of the class from current thread-local mrb_state.
  • Avoid to create new mrb_state.
  • Is it unsafely access?
• To avoid unexpected GC, I must mark the new obj.
  • Stop GC temporarily by calling mrb_gc_register()
  • And restart GC by calling mrb_gc_unregister()
  • It has a risk of missing mrb_gc_unregister() so I should take RAII approach, for example using shared_ptr.
• Insert a new TransactionPlugin registers hooks and has hook handler functions.
  • Execute the obj by calling mrb_funcall_*()

[syucream]

progress

Tried to fix #74 (comment) by c753613.

new issue

• Detect unusable class/method usage.
  • For example, ATS::echo is unavailable at late hook.
  • Should these calling raise an exception?

[coveralls]

Coverage decreased (-51.7%) to 0.0% when pulling 98dacd8 on feature/hook_prototype into f4b525a on master.

[coveralls]

Coverage decreased (-51.7%) to 0.0% when pulling 98dacd8 on feature/hook_prototype into f4b525a on master.

[syucream]

To detect unusable class/method usage, plugin must pass hook timing to the transaction because atscppapi::Transaction doesn't have hook info API.

[coveralls]

Coverage decreased (-51.7%) to 0.0% when pulling 42bf9bb on feature/hook_prototype into f4b525a on master.

[coveralls]

Coverage decreased (-51.7%) to 0.0% when pulling 54f187d on feature/hook_prototype into f4b525a on master.

[syucream]

TSMrubyValue implemented at c753613 has non-thread-safe function.
At a5dd106, I try implementing an another approach.

[coveralls]

Coverage decreased (-51.7%) to 0.0% when pulling a5dd106 on feature/hook_prototype into f4b525a on master.

[coveralls]

Coverage decreased (-51.7%) to 0.0% when pulling 5ba68e8 on feature/hook_prototype into f4b525a on master.

[syucream]

Modify unit test code

Its a big task. I fix it as another issue.
#75

[coveralls]

Coverage decreased (-51.7%) to 0.0% when pulling 706c841 on feature/hook_prototype into f4b525a on master.

[coveralls]

Coverage decreased (-51.7%) to 0.0% when pulling a999df4 on feature/hook_prototype into f4b525a on master.