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lib/membrane/rtp/utils.ex

defmodule Membrane.RTP.Utils do
@moduledoc false
@spec strip_padding(binary, padding_present? :: boolean) ::
{:ok, {binary, padding_size :: non_neg_integer()}} | :error
def strip_padding(binary, padding_present?)
def strip_padding(binary, false), do: {:ok, {binary, 0}}
def strip_padding(binary, true) do
with size when size > 0 <- byte_size(binary),
padding_size = :binary.last(binary),
payload_size = byte_size(binary) - padding_size,
<<stripped_payload::binary-size(payload_size), _::binary-size(padding_size)>> <- binary do
{:ok, {stripped_payload, padding_size}}
else
_error -> :error
end
end
@spec align(payload :: binary, align_to :: pos_integer()) ::
{binary, padding_size :: non_neg_integer()}
def align(payload, align_to) do
case rem(byte_size(payload), align_to) do
0 ->
{payload, 0}
padding_size ->
zeros_no = padding_size - 1
{<<payload::binary, 0::size(zeros_no)-unit(8), padding_size>>, padding_size}
end
end
@spec from_which_rollover(number() | nil, number(), number()) :: :current | :previous | :next
def from_which_rollover(previous_value, new_value, rollover_length)
def from_which_rollover(nil, _new, _rollover_length), do: :current
def from_which_rollover(previous_value, new_value, rollover_length) do
# a) current rollover
distance_if_current = abs(previous_value - new_value)
# b) new_value is from the previous rollover
distance_if_previous = abs(previous_value - (new_value - rollover_length))
# c) new_value is in the next rollover
distance_if_next = abs(previous_value - (new_value + rollover_length))
[
{:current, distance_if_current},
{:previous, distance_if_previous},
{:next, distance_if_next}
]
|> Enum.min_by(fn {_atom, distance} -> distance end)
|> then(fn {result, _value} -> result end)
end
end