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Avoid per-byte binary construction and backtracking in Plug.Conn.Utils.token/1 #1335

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Merged
josevalim merged 1 commit into from
Oct 23, 2026
+29 −10
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Avoid per-byte binary construction and backtracking in Plug.Conn.Utils.token/1 #1335

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39 changes: 29 additions & 10 deletions lib/plug/conn/utils.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -239,23 +239,42 @@ defmodule Plug.Conn.Utils do

"""
@spec token(binary) :: binary | false
def token(""), do: false
def token(<<?", quoted::binary>>), do: quoted_token(quoted, "")
def token(token), do: unquoted_token(token, "")
def token(token) when is_binary(token), do: do_token(token, token)

defp do_token(<<token::binary>>, original), do: unquoted_token(token, original, 0)

defp quoted_token(<<>>, _acc), do: false
defp quoted_token(<<?", t::binary>>, acc), do: strip_spaces(t) == "" and acc
defp quoted_token(<<?\\, h, t::binary>>, acc), do: quoted_token(t, <<acc::binary, h>>)

defp quoted_token(<<?\\, rest::binary>>, acc) do
case rest do
<<h, t::binary>> -> quoted_token(t, <<acc::binary, h>>)
<<>> -> false
end
end

defp quoted_token(<<h, t::binary>>, acc), do: quoted_token(t, <<acc::binary, h>>)
defp quoted_token(<<>>, _acc), do: false

defp unquoted_token(<<?", quoted::binary>>, _token, len),
do: len == 0 and quoted_token(quoted, "")

defp unquoted_token(<<?\r, rest::binary>>, token, len) do
case rest do
<<?\n, t::binary>> -> strip_spaces(t) == "" and binary_part(token, 0, len)
_ -> false
end
end

defp unquoted_token(<<>>, acc), do: acc
defp unquoted_token("\r\n" <> t, acc), do: strip_spaces(t) == "" and acc
defp unquoted_token(<<h, t::binary>>, acc) when h in @space, do: strip_spaces(t) == "" and acc
defp unquoted_token(<<h, t::binary>>, token, len) when h in @space,
do: strip_spaces(t) == "" and binary_part(token, 0, len)

defp unquoted_token(<<h, _::binary>>, _acc) when h in @specials or h < 32 or h === 127,
defp unquoted_token(<<h, _::binary>>, _token, _len) when h in @specials or h < 32 or h === 127,
do: false

defp unquoted_token(<<h, t::binary>>, acc), do: unquoted_token(t, <<acc::binary, h>>)
defp unquoted_token(<<_, t::binary>>, token, len),
do: unquoted_token(t, token, len + 1)

defp unquoted_token(<<>>, token, len), do: len != 0 and token

@doc """
Parses a comma-separated list of header values.
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