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module Msf::Exploit::Retry
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  # Retry the block until it returns a truthy value. Each iteration attempt will
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  # be performed with an exponential backoff. If the timeout period surpasses,
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  # nil is returned.
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  #
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  # @param Integer timeout the number of seconds to wait before the operation times out
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  # @return the truthy value of the block is returned or nil if it timed out
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  def retry_until_truthy(timeout:)
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    start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC, :second)
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    ending_time = start_time + timeout
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    retry_count = 0
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    while Process.clock_gettime(Process::CLOCK_MONOTONIC, :second) < ending_time
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      result = yield
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      return result if result
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      retry_count += 1
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      remaining_time_budget = ending_time - Process.clock_gettime(Process::CLOCK_MONOTONIC, :second)
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      break if remaining_time_budget <= 0
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      delay = 2**retry_count
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      if delay >= remaining_time_budget
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        delay = remaining_time_budget
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        vprint_status("Final attempt. Sleeping for the remaining #{delay} seconds out of total timeout #{timeout}")
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      else
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        vprint_status("Sleeping for #{delay} seconds before attempting again")
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      end
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      sleep delay
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    end
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    nil
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  end
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end
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