Class: LargeObjectStore::RailsWrapper

Inherits:
Object
  • Object
show all
Defined in:
lib/large_object_store.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(store) ⇒ RailsWrapper

Returns a new instance of RailsWrapper.



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# File 'lib/large_object_store.rb', line 24

def initialize(store)
  @store = store
end

Instance Attribute Details

#store ⇒ Object (readonly)

Returns the value of attribute store.



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# File 'lib/large_object_store.rb', line 22

def store
  @store
end

Instance Method Details

#delete(key) ⇒ Object 



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# File 'lib/large_object_store.rb', line 98

def delete(key)
  @store.delete(key(key, 0))
end

#exist?(key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/large_object_store.rb', line 94

def exist?(key)
  @store.exist?(key(key, 0))
end

#fetch(key, options = {}) ⇒ Object 



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# File 'lib/large_object_store.rb', line 86

def fetch(key, options={})
  value = read(key)
  return value unless value.nil?
  value = yield
  write(key, value, options)
  value
end

#read(key) ⇒ Object 



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# File 'lib/large_object_store.rb', line 59

def read(key)
  # read pages
  pages, uuid = @store.read(key(key, 0))
  return if pages.nil?

  data = if pages.is_a?(Fixnum)
    # read sliced data
    keys = (1..pages).map { |i| key(key, i) }
    # use values_at to enforce key order because read_multi doesn't guarantee a return order
    slices = @store.read_multi(*keys).values_at(*keys)
    return nil if slices.compact.size != pages

    slices = slices.map do |slice|
      s = slice.dup
      [s.slice!(0, UUID_SIZE), s]
    end

    return nil unless slices.map(&:first).uniq == [uuid]

    slices.map!(&:last).join("")
  else
    pages
  end

  deserialize(data)
end

#write(key, value, options = {}) ⇒ Object 



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# File 'lib/large_object_store.rb', line 28

def write(key, value, options = {})
  options = options.dup
  value = serialize(value, options)

  # calculate slice size; note that key length is a factor because
  # the key is stored on the same slab page as the value
  slice_size = MAX_OBJECT_SIZE - ITEM_HEADER_SIZE - UUID_SIZE - key.bytesize

  # store number of pages
  pages = (value.size / slice_size.to_f).ceil

  if pages == 1
    !!@store.write(key(key, 0), value, options)
  else
    # store meta
    uuid = SecureRandom.hex(UUID_BYTES)
    return false unless @store.write(key(key, 0), [pages, uuid], options) # invalidates the old cache

    # store object
    page = 1
    loop do
      slice = value.slice!(0, slice_size)
      break if slice.size == 0

      return false unless @store.write(key(key, page), slice.prepend(uuid), options.merge(raw: true))
      page += 1
    end
    true
  end
end