cogini / http_structured_field

Elixir library to parse HTTP Structured Fields (RFC 8941)

http_structured_field

Elixir library to parse and generate RFC 8941 Structured Field Values for HTTP.

HTTP headers often need to carry complex structures such as lists of values. RFC 8941 specifies a standard format for these fields independent of the RFCs that define the headers.

Following are some headers that use the format:

• Permissions-Policy
• Document-Policy
• Reporting-Endpoints
• BFCache-Opt-In
• Accept-CH
• Critical-CH
• Supports-Loading-Mode
• Signed-Headers
• Sec-Redemption-Record
• Sec-Signature

Usage

iex> HttpStructuredField.parse("42")
{:ok, {:integer, 42}}

iex> HttpStructuredField.parse("4.5")
{:ok, {:decimal, 4.5}}

iex> HttpStructuredField.parse("?1")
{:ok, {:boolean, true}}

iex> HttpStructuredField.parse(~S("hello world"))
{:ok, {:string, "hello world"}}

iex> HttpStructuredField.parse("foo123/456")
{:ok, {:token, "foo123/456"}}

iex> HttpStructuredField.parse(":cHJldGVuZCB0aGlzIGlzIGJpbmFyeSBjb250ZW50Lg==:")
{:ok, {:binary, "pretend this is binary content."}}

iex> HttpStructuredField.parse("1; abc; b=?0")
{:ok, {:integer, 1, [{"abc", {:boolean, true}}, {"b", {:boolean, false}}]}}

iex> HttpStructuredField.parse("foo, bar")
{:ok, [{:token, "foo"}, {:token, "bar"}]}

iex> HttpStructuredField.parse("a=(1 2), b=3, c=4;aa=bb, d=(5 6);valid", type: :dict)
{:ok, [
  {"a", {:inner_list, [integer: 1, integer: 2]}},
  {"b", {:integer, 3}},
  {"c", {:integer, 4, [{"aa", {:token, "bb"}}]}},
  {"d", {:inner_list, [integer: 5, integer: 6], [{"valid", {:boolean, true}}]}}
]}

The parser uses NimbleParsec, so it's strict, unlike, e.g., regular expressions.

It handles the funky syntax of parameters, nested lists, and dictionaries. You can run it on any input and it will return a tagged tuple for a simple value or an Elixir list for a list of values. If there are parameters, then the tuple will have three elements, with the third being a list. Inner List types are tagged tuples, as we need some place to put the parameters.

Parmeters and dictionary members are represented as lists of tuples where the name is the first tuple element.

Dictionary types are unfortunately incompatible with lists, so you have to tell the parser what to expect by adding the type: :dict option.

Installation

If available in Hex, the package can be installed by adding http_structured_field to your list of dependencies in mix.exs:

def deps do
  [
    {:http_structured_field, "~> 0.1.0"}
  ]
end

The docs can be found at https://hexdocs.pm/http_structured_field.