Class: Ole::Storage::RangesIOMigrateable

Inherits:
RangesIOResizeable show all
Defined in:
lib/ole/storage/base.rb

Overview

like RangesIOResizeable, but Ole::Storage::Dirent specific. provides for migration between bats based on size, and updating the dirent.

Instance Attribute Summary collapse

Attributes inherited from RangesIOResizeable

#bat

Attributes inherited from RangesIO

#io, #mode, #pos, #ranges, #size

Instance Method Summary collapse

Methods inherited from RangesIO

#close, #eof?, #gets, #inspect, open, #read, #rewind, #write

Constructor Details

#initialize(dirent, mode = 'r') ⇒ RangesIOMigrateable

Returns a new instance of RangesIOMigrateable.



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# File 'lib/ole/storage/base.rb', line 636

def initialize dirent, mode='r'
  @dirent = dirent
  super @dirent.ole.bat_for_size(@dirent.size), mode,
    :first_block => @dirent.first_block, :size => @dirent.size
end

Instance Attribute Details

#dirent ⇒ Object (readonly)

Returns the value of attribute dirent.



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# File 'lib/ole/storage/base.rb', line 635

def dirent
  @dirent
end

Instance Method Details

#first_block ⇒ Object

forward this to the dirent



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# File 'lib/ole/storage/base.rb', line 671

def first_block
  @dirent.first_block
end

#first_block=(val) ⇒ Object 



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# File 'lib/ole/storage/base.rb', line 675

def first_block= val
  @dirent.first_block = val
end

#truncate(size) ⇒ Object 



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# File 'lib/ole/storage/base.rb', line 642

def truncate size
  bat = @dirent.ole.bat_for_size size
  if bat.class != @bat.class
    # bat migration needed! we need to backup some data. the amount of data
    # should be <= @ole.header.threshold, so we can just hold it all in one buffer.
    # backup this
    pos = [@pos, size].min
    self.pos = 0
    keep = read [@size, size].min
    # this does a normal truncate to 0, removing our presence from the old bat, and
    # rewrite the dirent's first_block
    super 0
    @bat = bat
    # just change the underlying io from right under everyone :)
    @io = bat.io
    # important to do this now, before the write. as the below write will always
    # migrate us back to sbat! this will now allocate us +size+ in the new bat.
    super
    self.pos = 0
    write keep
    self.pos = pos
  else
    super
  end
  # now just update the file
  @dirent.size = size
end