Sml.Parser (SmlEx v0.1.0)

Copy Markdown View Source

Low-level parser for the SML binary encoding (type-length-value).

Every element starts with one or more TL bytes:

bit 7     more TL bytes follow
bits 6-4  type: 000 octet string, 100 boolean, 101 integer,
                110 unsigned, 111 list
bits 3-0  length nibble

With multiple TL bytes the length nibbles are concatenated. For lists the length is the number of elements; for all other types it is the number of bytes including the TL bytes.

Elements are mapped to plain Elixir terms:

SMLElixir
octet stringbinary
booleantrue / false
integer / unsignedinteger
listlist
0x01 (optional, absent)nil
0x00 (end of message):end_of_message

Signedness is lost in this representation; Sml.Decoder knows the schema and does not need it.

Summary

Types

error()
term_t()

Functions

parse(data)

Parses one element from the beginning of data.

parse_all(data)

Parses all elements in data until it is exhausted.

parse_list_header(data)

Parses only the TL header of a list and returns its element count.

parse_many(data, count)

Parses count consecutive elements.

Types

error()

@type error() :: {:error, reason :: atom() | tuple(), rest :: binary()}

term_t()

@type term_t() ::
  binary() | boolean() | integer() | nil | :end_of_message | [term_t()]

Functions

parse(data)

@spec parse(binary()) :: {:ok, term_t(), binary()} | error()

Parses one element from the beginning of data.

Returns the element and the remaining bytes. On failure the remaining bytes point at the element that could not be parsed.

iex> Sml.Parser.parse(<<0x62, 0x1E, 0xFF>>)
{:ok, 30, <<0xFF>>}

iex> Sml.Parser.parse(<<0x72, 0x03, "EM", 0x52, 0xFF>>)
{:ok, ["EM", -1], ""}

parse_all(data)

@spec parse_all(binary()) :: {:ok, [term_t()]} | error()

Parses all elements in data until it is exhausted.

Handy for inspecting unknown data:

iex> Sml.Parser.parse_all(<<0x01, 0x42, 0x01, 0x00>>)
{:ok, [nil, true, :end_of_message]}

parse_list_header(data)

@spec parse_list_header(binary()) :: {:ok, non_neg_integer(), binary()} | error()

Parses only the TL header of a list and returns its element count.

parse_many(data, count)

@spec parse_many(binary(), non_neg_integer()) :: {:ok, [term_t()], binary()} | error()

Parses count consecutive elements.