Module: Ownership

Included in:
Magick::Image
Defined in:
lib/httpthumbnailer/ownership.rb

Constant Summary collapse

UseDestroyedError = 
Class.new(RuntimeError)
BorrowingDestoryedError = 
Class.new(RuntimeError)
BorrowingNotOwnedError = 
Class.new(RuntimeError)

Instance Method Summary collapse

Instance Method Details

#borrow ⇒ Object 



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# File 'lib/httpthumbnailer/ownership.rb', line 14

def borrow
  @destroyed and Kernel::raise BorrowingDestoryedError, "cannot borrow a destroyed obejct '#{self}'"
  @owned or Kernel::raise BorrowingNotOwnedError, "cannot borrow not owned object '#{self}'"
  was_borrowed = @borrowed
  begin
    @borrowed = true
    yield self
  ensure
    @borrowed = was_borrowed
  end
end

#borrowed? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/httpthumbnailer/ownership.rb', line 10

def borrowed?
  @borrowed
end

#get(&block) ⇒ Object 



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# File 'lib/httpthumbnailer/ownership.rb', line 26

def get(&block)
  if @borrowed
    borrow(&block)
  else
    @destroyed and Kernel::raise UseDestroyedError, "cannot own a destoryed object '#{self}'"
    # take ownership; it may be owned already
    @owned = true
    begin
      ret = yield self
      # give up ownership if nothing happened with the obejct
      # NOTE: we use equal here sice == may actually test pixel by pixel which is not the point!
      if ret.equal?(self) or ret.nil?
        @owned = nil
        return self
      end
      ret
    ensure
      # if I am still an owner destroy and give up ownership
      if @owned
        destroy!
        @destroyed = true
        @owned = nil
      end
    end
  end
end

#owned? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/httpthumbnailer/ownership.rb', line 6

def owned?
  @owned
end