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Load BTree.FreeList entries
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lib/btree/free_list.ex
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lib/btree/free_list.ex
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@spec load(BTree.t) :: :ok
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def load(%BTree{} = btree) do
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%{
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store: store,
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free_list: free_list,
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free_list_tail_address: {tail_index, tail_checksum},
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free_list_max_index: free_list_max_index,
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opts: %{
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page_size: opt_page_size,
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},
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} = btree
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# Load max_index
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:ets.insert(free_list, {:max_index, free_list_max_index})
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# Load FreeList entries from the linked list of pages
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free_list_page_indexes = do_load_page(store, free_list, opt_page_size, tail_index, tail_checksum, [])
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# Free the pages used to store the list itself
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# (they will be pending until the next commit so they won't be overwritten during this cycle)
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Enum.each(free_list_page_indexes, fn index ->
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free_page(free_list, index)
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end)
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:ok
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end
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defp do_load_page(_store, _free_list_tail_address, _opt_page_size, 0 = _index, _checksum, indexes_acc) do
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indexes_acc
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end
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defp do_load_page(store, free_list, opt_page_size, index, checksum, indexes_acc) do
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page_data = Store.read_page(store, index, checksum)
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<<
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_::binary-size(opt_page_size - c_free_list_page_trailer_size()),
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entries_size::integer-64,
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prev_index::integer-64,
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prev_checksum::binary-16,
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>> = page_data
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<<
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entries_data::binary-size(entries_size),
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_::binary,
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>> = page_data
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:ok = do_load_entries(entries_data, free_list)
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indexes_acc = [index | indexes_acc]
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do_load_page(store, free_list, opt_page_size, prev_index, prev_checksum, indexes_acc)
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end
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defp do_load_entries("", _free_list), do: :ok
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# See constant: c_free_list_entry_size()
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defp do_load_entries(<<index::integer-64, entries_rest::binary>>, free_list) do
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:ets.insert(free_list, {[:free | index], nil})
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do_load_entries(entries_rest, free_list)
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end
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@spec flush(BTree.t) :: %{free_list_tail_address: {non_neg_integer, binary}, free_list_max_index: non_neg_integer}
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def flush(%BTree{} = btree) do
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%{
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end
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defp do_flush(store, free_list, opt_page_size, subspace, page_acc, last_address, last_key) do
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entries_size_max = opt_page_size - c_address_bytes()
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entries_size_max = opt_page_size - c_free_list_page_trailer_size()
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case :ets.next(free_list, last_key) do
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[^subspace | index] = key ->
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defp write_free_list_page(store, free_list, opt_page_size, page_data, last_address) do
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{last_index, last_checksum} = last_address
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pad_bytes = opt_page_size - byte_size(page_data) - c_address_bytes()
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entries_size = byte_size(page_data)
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pad_bytes = opt_page_size - entries_size - c_free_list_page_trailer_size()
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assert pad_bytes >= 0
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page_data = <<
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page_data::binary,
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0::integer-unit(8)-size(pad_bytes),
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entries_size::integer-64,
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last_index::integer-64,
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last_checksum::binary-16,
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>>