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Add structure encoding
+176
-1
+162
lib/encoding/structure.ex
+162
lib/encoding/structure.ex
···
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defmodule Hobbes.Encoding.Structure do
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import ExUnit.Assertions, only: [assert: 1]
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@escape 0xFF
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@int_neg_8 0x0C
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@int_neg_7 0x0D
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@int_neg_6 0x0E
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@int_neg_5 0x0F
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@int_neg_4 0x10
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@int_neg_3 0x11
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@int_neg_2 0x12
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@int_neg_1 0x13
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@int_0 0x14
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@int_pos_1 0x15
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@int_pos_2 0x16
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@int_pos_3 0x17
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@int_pos_4 0x18
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@int_pos_5 0x1A
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@int_pos_6 0x1B
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@int_pos_7 0x1C
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@int_pos_8 0x1D
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def pack(fields) do
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encode(fields, "", "", 0)
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end
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def unpack(bin) do
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{header_fields, body_data} = decode_header(bin, [], 0, 0)
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Enum.map(header_fields, fn {id, type, pos, size} ->
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value = decode_value(type, pos, size, body_data)
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{id, value}
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end)
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end
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defp encode([], header_acc, body_acc, _last_id) do
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<<
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header_acc::binary,
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<<@escape>>,
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body_acc::binary,
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>>
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end
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defp encode([field | fields_rest], header_acc, body_acc, last_id) do
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{field_id, field_value} = field
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assert field_id > last_id
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id_diff_enc = encode_varint(field_id - last_id)
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{field_head, field_body} = encode_field(field_value)
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header_acc = <<
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header_acc::binary,
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field_head::binary,
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id_diff_enc::binary,
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>>
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body_acc = <<
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body_acc::binary,
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field_body::binary,
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>>
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encode(fields_rest, header_acc, body_acc, field_id)
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end
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defp encode_field(int) when is_integer(int) and int < 0 do
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binary = :binary.encode_unsigned(-int)
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case byte_size(binary) do
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8 -> {<<@int_neg_8>>, binary}
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7 -> {<<@int_neg_7>>, binary}
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6 -> {<<@int_neg_6>>, binary}
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5 -> {<<@int_neg_5>>, binary}
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4 -> {<<@int_neg_4>>, binary}
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3 -> {<<@int_neg_3>>, binary}
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2 -> {<<@int_neg_2>>, binary}
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1 -> {<<@int_neg_1>>, binary}
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end
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end
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defp encode_field(0) do
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{<<@int_0>>, ""}
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end
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defp encode_field(int) when is_integer(int) and int > 0 do
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binary = :binary.encode_unsigned(int)
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case byte_size(binary) do
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1 -> {<<@int_pos_1>>, binary}
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2 -> {<<@int_pos_2>>, binary}
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3 -> {<<@int_pos_3>>, binary}
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4 -> {<<@int_pos_4>>, binary}
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5 -> {<<@int_pos_5>>, binary}
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6 -> {<<@int_pos_6>>, binary}
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7 -> {<<@int_pos_7>>, binary}
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8 -> {<<@int_pos_8>>, binary}
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end
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end
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defp decode_header(<<@escape, rest::binary>>, acc, _pos, _id_last) do
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{Enum.reverse(acc), rest}
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end
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defp decode_header(<<type::integer-8, rest::binary>>, acc, pos, id_last) do
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{size, rest} = decode_size(type, rest)
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{id_diff, rest} = decode_varint(rest)
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id = id_last + id_diff
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acc = [{id, type, pos, size} | acc]
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pos = pos + size
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decode_header(rest, acc, pos, id)
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end
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defp decode_size(@int_neg_8, bin), do: {8, bin}
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defp decode_size(@int_neg_7, bin), do: {7, bin}
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defp decode_size(@int_neg_6, bin), do: {6, bin}
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defp decode_size(@int_neg_5, bin), do: {5, bin}
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defp decode_size(@int_neg_4, bin), do: {4, bin}
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defp decode_size(@int_neg_3, bin), do: {3, bin}
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defp decode_size(@int_neg_2, bin), do: {2, bin}
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defp decode_size(@int_neg_1, bin), do: {1, bin}
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defp decode_size(@int_0, bin), do: {0, bin}
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defp decode_size(@int_pos_1, bin), do: {1, bin}
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defp decode_size(@int_pos_2, bin), do: {2, bin}
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defp decode_size(@int_pos_3, bin), do: {3, bin}
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defp decode_size(@int_pos_4, bin), do: {4, bin}
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defp decode_size(@int_pos_5, bin), do: {5, bin}
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defp decode_size(@int_pos_6, bin), do: {6, bin}
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defp decode_size(@int_pos_7, bin), do: {7, bin}
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defp decode_size(@int_pos_8, bin), do: {8, bin}
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@neg_int_types [
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@int_neg_1, @int_neg_2, @int_neg_3, @int_neg_4,
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@int_neg_5, @int_neg_6, @int_neg_7, @int_neg_8,
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]
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@pos_int_types [
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@int_pos_1, @int_pos_2, @int_pos_3, @int_pos_4,
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@int_pos_5, @int_pos_6, @int_pos_7, @int_pos_8,
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]
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defp decode_value(int_type, pos, size, data) when int_type in @neg_int_types do
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<<_prefix::binary-size(pos), int::integer-unit(8)-size(size), _rest::binary>> = data
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-int
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end
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defp decode_value(@int_0, _pos, _size, _data) do
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0
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end
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defp decode_value(int_type, pos, size, data) when int_type in @pos_int_types do
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<<_prefix::binary-size(pos), int::integer-unit(8)-size(size), _rest::binary>> = data
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int
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end
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defp encode_varint(int) do
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# TODO
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assert int < 128
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<<0::1, int::unsigned-integer-7>>
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end
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defp decode_varint(<<0::1, int::unsigned-integer-7, rest::binary>>) do
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{int, rest}
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end
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end
+14
-1
test/encoding_test.exs
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test/encoding_test.exs
···
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defmodule Hobbes.EncTest do
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use ExUnit.Case, async: true
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alias Hobbes.Encoding.Keyset
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alias Hobbes.Encoding.{Keyset, Structure}
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@moduletag :encoding
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···
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assert "\x1D" <> rest = Keyset.pack([(2 ** 64) - 1])
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assert rest == String.duplicate("\xFF", 8)
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end
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end
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describe "structure" do
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test "encode" do
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fields = [
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{2, 123},
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{3, -1_000_000},
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{6, 0},
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]
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bin = Structure.pack(fields)
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assert Structure.unpack(bin) == fields
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end
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end
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end