Class: Cmds::IOHandler

Inherits:
Object
  • Object
show all
Defined in:
lib/cmds/io_handler.rb

Overview

Class for handling IO from threads and passing it back via a Queue to the main thread for processing.

NOTE These are one-use only! Don't try to reuse them.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ IOHandler

Returns a new instance of IOHandler.



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# File 'lib/cmds/io_handler.rb', line 10

def initialize
  @in = nil
  @out = $stdout
  @err = $stderr
  
  # Initialize a thread-safe queue for passing output from the IO threads
  # back to the main thread
  # 
  # NOTE  This used to be done in {#start}, but I was seeing intermittent
  #       failures on Travis from what look like thread race conditions,
  #       guessing that it's from output arriving before {#start} is
  #       called, which totally looks like it could happen.
  #       
  #       See the failure in
  #       
  #       https://travis-ci.org/nrser/qb/jobs/348609316
  #       
  #       Really, I'm surprised I haven't hit more issues with this
  #       half-ass threading shit.
  #       
  #       Anyways, I moved the queue creation here, see if it helps.
  # 
  @queue = Queue.new
  
  # Flag that is set to `true` when {#start} is called.
  @started = false
end

Instance Attribute Details

#err ⇒ Object

Returns the value of attribute err.



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# File 'lib/cmds/io_handler.rb', line 8

def err
  @err
end

#in ⇒ Object

Returns the value of attribute in.



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# File 'lib/cmds/io_handler.rb', line 8

def in
  @in
end

#out ⇒ Object

Returns the value of attribute out.



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# File 'lib/cmds/io_handler.rb', line 8

def out
  @out
end

Instance Method Details

#on_err(&block) ⇒ Object 



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# File 'lib/cmds/io_handler.rb', line 57

def on_err &block
  @err = block
end

#on_out(&block) ⇒ Object 



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# File 'lib/cmds/io_handler.rb', line 48

def on_out &block
  @out = block
end

#start ⇒ Object 



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# File 'lib/cmds/io_handler.rb', line 71

def start
  if @started
    raise "This handler has already been started / run"
  end
  
  @started = true
  
  # if out is a proc, it's not done
  out_done = ! @out.is_a?(Proc)
  # same for err
  err_done = ! @err.is_a?(Proc)

  until out_done && err_done
    key, line = @queue.pop
    
    case key
    when :out
      if line.nil?
        out_done = true
      else
        handle_line @out, line
      end

    when :err
      if line.nil?
        err_done = true
      else
        handle_line @err, line
      end

    else
      raise "bad key: #{ key.inspect }"
    end
  end
end

#thread_send_err(line) ⇒ Object

called in separate thread handling process IO



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# File 'lib/cmds/io_handler.rb', line 62

def thread_send_err line
  @queue << [:err, line]
end

#thread_send_line(sym, line) ⇒ Object

called in separate thread handling process IO



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# File 'lib/cmds/io_handler.rb', line 67

def thread_send_line sym, line
  @queue << [sym, line]
end

#thread_send_out(line) ⇒ Object

called in separate thread handling process IO



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# File 'lib/cmds/io_handler.rb', line 53

def thread_send_out line
  @queue << [:out, line]
end