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Posted By

neil on 04/07/08

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Last Edited at 04/07/08 07:17am

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file_duplication

/ Published in: Ruby
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  1. require 'initialized_by_hash'
  2.  
  3.  
  4. # copies a file, providing feedback on the progress of the operation.
  5. #
  6. #  source:       a path to the file that should be duplicated
  7. #  destination:  a path to the the new copy
  8. #  report_rate:  the number of times each second to report
  9. #
  10. # example:
  11. #   fd = FileDuplication.new :source => ARGV[0], :destination => ARGV[1]
  12. #   fd.begin do | bytes_done, bytes_left|
  13. #     puts '%i %i' % [ bytes_done, bytes_left]
  14. #   end
  15. #
  16. class FileDuplication
  17.  
  18.   attr_accessor :source, :destination, :report_rate
  19.  
  20.   initialized_by_hash
  21.  
  22.  
  23.  private
  24.  
  25.   def fill_in_blanks
  26.     @report_rate = 10 unless @report_rate
  27.   end
  28.  
  29.  
  30.  public
  31.  
  32.   # begins this file duplication operation, providing feedback to the default
  33.   # block as the operation progresses.
  34.   #
  35.   def begin
  36.     # check that both source and destination have been specified
  37.     raise 'cannot copy from an unspecified source' unless @source
  38.     raise 'cannot copy to unspecified destination' unless @destination
  39.  
  40.     begin
  41.       source = File.open @source
  42.       sink   = File.open @destination, 'w'
  43.  
  44.       bytes_done         = 0
  45.       bytes_left         = File.size @source
  46.       when_last_reported = Time.at 0
  47.       scrap              = ''
  48.  
  49.       # report the commencement of the operation
  50.       yield  bytes_done, bytes_left
  51.  
  52.       # while there are still some bytes left to copy..
  53.       while 0 < bytes_left do
  54.  
  55.         # don't try to copy more bytes than are left to copy
  56.         block_size = [ 10240, bytes_left].min
  57.  
  58.         # copy the bytes in the focus block
  59.         source.sysread block_size, scrap
  60.         sink.syswrite scrap
  61.  
  62.         bytes_done += block_size
  63.         bytes_left -= block_size
  64.  
  65.         # if enough time has passed that another report should be made..
  66.         now = Time.now
  67.         if when_last_reported + 1.0 / @report_rate <= now
  68.  
  69.           # report on progress
  70.           yield  bytes_done, bytes_left
  71.  
  72.           when_last_reported = now
  73.         end
  74.       end
  75.  
  76.       # report the completion of the operation
  77.       yield  bytes_done, bytes_left
  78.  
  79.     ensure
  80.  
  81.       sink.close if sink
  82.       source.close if source
  83.     end
  84.   end
  85.  
  86. end
  87.  
  88. # --------------------------------------------------------------- 80 column rule

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