MqttX.Packet.Varint (MqttX v0.10.0)

MQTT Variable Byte Integer encoding and decoding.

Variable byte integers use 1-4 bytes to encode values from 0 to 268,435,455. Each byte uses 7 bits for data and 1 continuation bit.

Encoding

iex> MqttX.Packet.Varint.encode(127)
<<127>>

iex> MqttX.Packet.Varint.encode(128)
<<128, 1>>

iex> MqttX.Packet.Varint.encode(16383)
<<255, 127>>

iex> MqttX.Packet.Varint.decode(<<128, 1, "rest">>)
{:ok, 128, "rest"}

byte_length(i)

Calculate the byte length needed to encode a value.

decode(arg)

Decode a variable byte integer from binary data.

encode(i)

Encode an integer as a variable byte integer.

encode_iodata(i)

Encode an integer as iodata (more efficient for building packets).

max_value()

Maximum value that can be encoded.

@spec byte_length(non_neg_integer()) :: 1 | 2 | 3 | 4

Calculate the byte length needed to encode a value.

@spec decode(binary()) ::
  {:ok, non_neg_integer(), binary()} | :incomplete | {:error, atom()}

Decode a variable byte integer from binary data.

Returns {:ok, value, rest} on success, :incomplete if more data needed, or {:error, reason} on failure.

@spec encode(non_neg_integer()) :: binary()

Encode an integer as a variable byte integer.

Returns a binary of 1-4 bytes.

@spec encode_iodata(non_neg_integer()) :: iodata()

Encode an integer as iodata (more efficient for building packets).

@spec max_value() :: non_neg_integer()

Maximum value that can be encoded.