Class: Ole::Storage::RangesIOResizeable

Inherits:
RangesIO
  • Object
show all
Defined in:
lib/ole/storage/base.rb

Overview

like normal RangesIO, but Ole::Storage specific. the ranges are backed by an AllocationTable, and can be resized. used for read/write to 2 streams:

  1. serialized dirent data

  2. sbat table data

  3. all dirents but through RangesIOMigrateable below

Note that all internal access to first_block is through accessors, as it is sometimes useful to redirect it.

Direct Known Subclasses

RangesIOMigrateable

Instance Attribute Summary collapse

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(bat, mode = 'r', params = {}) ⇒ RangesIOResizeable

Returns a new instance of RangesIOResizeable.

Raises:

  • (ArgumentError) 


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# File 'lib/ole/storage/base.rb', line 604

def initialize bat, mode='r', params={}
  mode, params = 'r', mode if Hash === mode
  first_block, size = params.values_at :first_block, :size
  raise ArgumentError, 'must specify first_block' unless first_block
  @bat = bat
  self.first_block = first_block
  # we now cache the blocks chain, for faster resizing.
  @blocks = @bat.chain first_block
  super @bat.io, mode, :ranges => @bat.ranges(@blocks, size)
end

Instance Attribute Details

#bat ⇒ Object (readonly)

Returns the value of attribute bat.



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# File 'lib/ole/storage/base.rb', line 602

def bat
  @bat
end

#first_block ⇒ Object

Returns the value of attribute first_block.



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# File 'lib/ole/storage/base.rb', line 603

def first_block
  @first_block
end

Instance Method Details

#truncate(size) ⇒ Object 



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# File 'lib/ole/storage/base.rb', line 615

def truncate size
  # note that old_blocks is != @ranges.length necessarily. i'm planning to write a
  # merge_ranges function that merges sequential ranges into one as an optimization.
  @bat.resize_chain @blocks, size
  @pos = size if @pos > size
  self.ranges = @bat.ranges(@blocks, size)
  self.first_block = @blocks.empty? ? AllocationTable::EOC : @blocks.first

  # don't know if this is required, but we explicitly request our @io to grow if necessary
  # we never shrink it though. maybe this belongs in allocationtable, where smarter decisions
  # can be made.
  # maybe its ok to just seek out there later??
  max = @ranges.map { |pos, len| pos + len }.max || 0
  @io.truncate max if max > @io.size
end