time/parsing/combinator/rfc/
rfc2822.rs

1//! Rules defined in [RFC 2822].
2//!
3//! [RFC 2822]: https://datatracker.ietf.org/doc/html/rfc2822
4
5use crate::parsing::combinator::rfc::rfc2234::wsp;
6use crate::parsing::combinator::{ascii_char, one_or_more, zero_or_more};
7use crate::parsing::ParsedItem;
8
9/// Consume the `fws` rule.
10// The full rule is equivalent to /\r\n[ \t]+|[ \t]+(?:\r\n[ \t]+)*/
11pub(crate) fn fws(mut input: &[u8]) -> Option<ParsedItem<'_, ()>> {
12    if let [b'\r', b'\n', rest @ ..] = input {
13        one_or_more(wsp)(rest)
14    } else {
15        input = one_or_more(wsp)(input)?.into_inner();
16        while let [b'\r', b'\n', rest @ ..] = input {
17            input = one_or_more(wsp)(rest)?.into_inner();
18        }
19        Some(ParsedItem(input, ()))
20    }
21}
22
23/// Consume the `cfws` rule.
24// The full rule is equivalent to any combination of `fws` and `comment` so long as it is not empty.
25pub(crate) fn cfws(input: &[u8]) -> Option<ParsedItem<'_, ()>> {
26    one_or_more(|input| fws(input).or_else(|| comment(input)))(input)
27}
28
29/// Consume the `comment` rule.
30fn comment(mut input: &[u8]) -> Option<ParsedItem<'_, ()>> {
31    input = ascii_char::<b'('>(input)?.into_inner();
32    input = zero_or_more(fws)(input).into_inner();
33    while let Some(rest) = ccontent(input) {
34        input = rest.into_inner();
35        input = zero_or_more(fws)(input).into_inner();
36    }
37    input = ascii_char::<b')'>(input)?.into_inner();
38
39    Some(ParsedItem(input, ()))
40}
41
42/// Consume the `ccontent` rule.
43fn ccontent(input: &[u8]) -> Option<ParsedItem<'_, ()>> {
44    ctext(input)
45        .or_else(|| quoted_pair(input))
46        .or_else(|| comment(input))
47}
48
49/// Consume the `ctext` rule.
50#[allow(clippy::unnecessary_lazy_evaluations)] // rust-lang/rust-clippy#8522
51fn ctext(input: &[u8]) -> Option<ParsedItem<'_, ()>> {
52    no_ws_ctl(input).or_else(|| match input {
53        [33..=39 | 42..=91 | 93..=126, rest @ ..] => Some(ParsedItem(rest, ())),
54        _ => None,
55    })
56}
57
58/// Consume the `quoted_pair` rule.
59fn quoted_pair(mut input: &[u8]) -> Option<ParsedItem<'_, ()>> {
60    input = ascii_char::<b'\\'>(input)?.into_inner();
61    input = text(input).into_inner();
62
63    // If nothing is parsed by `text`, this means by hit the `obs-text` rule and nothing matched.
64    // This is technically a success, and we used to check the `obs-qp` rule to ensure everything
65    // possible was consumed. After further analysis, it was determined that this check was
66    // unnecessary due to `obs-text` wholly subsuming `obs-qp` in this context. For this reason, if
67    // `text` fails to parse anything, we consider it a success without further consideration.
68
69    Some(ParsedItem(input, ()))
70}
71
72/// Consume the `no_ws_ctl` rule.
73const fn no_ws_ctl(input: &[u8]) -> Option<ParsedItem<'_, ()>> {
74    match input {
75        [1..=8 | 11..=12 | 14..=31 | 127, rest @ ..] => Some(ParsedItem(rest, ())),
76        _ => None,
77    }
78}
79
80/// Consume the `text` rule.
81fn text<'a>(input: &'a [u8]) -> ParsedItem<'a, ()> {
82    let new_text = |input: &'a [u8]| match input {
83        [1..=9 | 11..=12 | 14..=127, rest @ ..] => Some(ParsedItem(rest, ())),
84        _ => None,
85    };
86
87    let obs_char = |input: &'a [u8]| match input {
88        // This is technically allowed, but consuming this would mean the rest of the string is
89        // eagerly consumed without consideration for where the comment actually ends.
90        [b')', ..] => None,
91        [0..=9 | 11..=12 | 14..=127, rest @ ..] => Some(rest),
92        _ => None,
93    };
94
95    let obs_text = |mut input| {
96        input = zero_or_more(ascii_char::<b'\n'>)(input).into_inner();
97        input = zero_or_more(ascii_char::<b'\r'>)(input).into_inner();
98        while let Some(rest) = obs_char(input) {
99            input = rest;
100            input = zero_or_more(ascii_char::<b'\n'>)(input).into_inner();
101            input = zero_or_more(ascii_char::<b'\r'>)(input).into_inner();
102        }
103
104        ParsedItem(input, ())
105    };
106
107    new_text(input).unwrap_or_else(|| obs_text(input))
108}
time/parsing/combinator/rfc/rfc2822.rs

time/parsing/combinator/rfc/
rfc2822.rs
