Class: Generator

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/s3sync/thread_generator.rb

Overview

Generator converts an internal iterator (i.e. an Enumerable object) to an external iterator.

Example

require 'generator'

# Generator from an Enumerable object
g = Generator.new(['A', 'B', 'C', 'Z'])

while g.next?
  puts g.next
end

# Generator from a block
g = Generator.new { |g|
  for i in 'A'..'C'
    g.yield i
  end

  g.yield 'Z'
}

# The same result as above
while g.next?
  puts g.next
end

Instance Method Summary collapse

Constructor Details

#initialize(enum = nil, &block) ⇒ Generator

Creates a new generator either from an Enumerable object or from a block.

In the former, block is ignored even if given.

In the latter, the given block is called with the generator itself, and expected to call the yield method for each element.



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# File 'lib/s3sync/thread_generator.rb', line 66

def initialize(enum = nil, &block)
  if enum
    @block = proc{|g| enum.each{|value| g.yield value}}
  else
    @block = block
  end
  @index = 0
  @queue = []
  @main_thread = nil
  @loop_thread.kill if defined?(@loop_thread)
  @loop_thread = Thread.new do
    Thread.stop
    begin
      @block.call(self)
    rescue
      @main_thread.raise $!
    ensure
      @main_thread.wakeup
    end
  end
  Thread.pass until @loop_thread.stop?
  self
end

Instance Method Details

#current ⇒ Object

Returns the element at the current position.

Raises:

  • (EOFError) 


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# File 'lib/s3sync/thread_generator.rb', line 150

def current
  raise EOFError.new("no more elements available") if end?
  @queue.first
end

#each ⇒ Object

Rewinds the generator and enumerates the elements.



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# File 'lib/s3sync/thread_generator.rb', line 162

def each
  rewind
  until end?
    yield self.next
  end
  self
end

#end? ⇒ Boolean

Returns true if the generator has reached the end.

Returns:

  • (Boolean) 


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# File 'lib/s3sync/thread_generator.rb', line 107

def end?
  if @queue.empty?
    if @main_thread
      raise "should not be called in Generator.new{|g| ... }"
    end
    Thread.critical = true
    begin
      @main_thread = Thread.current
      @loop_thread.wakeup
      Thread.stop
    rescue ThreadError
      # ignore
    ensure
      @main_thread = nil
      Thread.critical = false
    end
  end
  @queue.empty?
end

#index ⇒ Object

Returns the current index (position) counting from zero.



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# File 'lib/s3sync/thread_generator.rb', line 133

def index
  @index
end

#next ⇒ Object

Returns the element at the current position and moves forward.

Raises:

  • (EOFError) 


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# File 'lib/s3sync/thread_generator.rb', line 143

def next
  raise EOFError.new("no more elements available") if end?
  @index += 1
  @queue.shift
end

#next? ⇒ Boolean

Returns true if the generator has not reached the end yet.

Returns:

  • (Boolean) 


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# File 'lib/s3sync/thread_generator.rb', line 128

def next?
  !end?
end

#pos ⇒ Object

Returns the current index (position) counting from zero.



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# File 'lib/s3sync/thread_generator.rb', line 138

def pos
  @index
end

#rewind ⇒ Object

Rewinds the generator.



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# File 'lib/s3sync/thread_generator.rb', line 156

def rewind
  initialize(nil, &@block) if @index.nonzero?
  self
end

#yield(value) ⇒ Object

Yields an element to the generator.



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# File 'lib/s3sync/thread_generator.rb', line 91

def yield(value)
  if Thread.current != @loop_thread
    raise "should be called in Generator.new{|g| ... }"
  end
  Thread.critical = true
  begin
    @queue << value
    @main_thread.wakeup
    Thread.stop
  ensure
    Thread.critical = false
  end
  self
end