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Offset parsing cleanup #1158

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merged 6 commits into from
Jun 29, 2023
Merged

Offset parsing cleanup #1158

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744da5e
Remove indirection for parsing timezone offset
djc Jun 29, 2023
9fa307a
Group imports from the same module
djc Jun 29, 2023
12d5943
Inline trivial single-use function
djc Jun 29, 2023
d79c3f3
Use std API for case-insensitive ASCII comparison
djc Jun 29, 2023
687b6d5
Fold zulu parsing into timezone_offset()
djc Jun 29, 2023
0c2269d
Fold permissive parsing into timezone_offset()
djc Jun 29, 2023
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23 changes: 16 additions & 7 deletions src/format/parse.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -213,7 +213,7 @@ fn parse_rfc3339<'a>(parsed: &mut Parsed, mut s: &'a str) -> ParseResult<(&'a st
parsed.set_nanosecond(nanosecond)?;
}

let offset = try_consume!(scan::timezone_offset_zulu(s, |s| scan::char(s, b':')));
let offset = try_consume!(scan::timezone_offset(s, |s| scan::char(s, b':'), true, false, true));
if offset <= -86_400 || offset >= 86_400 {
return Err(OUT_OF_RANGE);
}
Expand Down Expand Up @@ -445,7 +445,7 @@ where
}

&TimezoneName => {
try_consume!(scan::timezone_name_skip(s));
try_consume!(Ok((s.trim_start_matches(|c: char| !c.is_whitespace()), ())));
}

&TimezoneOffsetColon
Expand All @@ -454,24 +454,33 @@ where
| &TimezoneOffset => {
let offset = try_consume!(scan::timezone_offset(
s.trim_start(),
scan::colon_or_space
scan::colon_or_space,
false,
false,
true,
));
parsed.set_offset(i64::from(offset)).map_err(|e| (s, e))?;
}

&TimezoneOffsetColonZ | &TimezoneOffsetZ => {
let offset = try_consume!(scan::timezone_offset_zulu(
let offset = try_consume!(scan::timezone_offset(
s.trim_start(),
scan::colon_or_space
scan::colon_or_space,
true,
false,
true,
));
parsed.set_offset(i64::from(offset)).map_err(|e| (s, e))?;
}
&Internal(InternalFixed {
val: InternalInternal::TimezoneOffsetPermissive,
}) => {
let offset = try_consume!(scan::timezone_offset_permissive(
let offset = try_consume!(scan::timezone_offset(
s.trim_start(),
scan::colon_or_space
scan::colon_or_space,
true,
true,
true,
));
parsed.set_offset(i64::from(offset)).map_err(|e| (s, e))?;
}
Expand Down
120 changes: 36 additions & 84 deletions src/format/scan.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,24 +8,6 @@
use super::{ParseResult, INVALID, OUT_OF_RANGE, TOO_SHORT};
use crate::Weekday;

/// Returns true when two slices are equal case-insensitively (in ASCII).
/// Assumes that the `pattern` is already converted to lower case.
fn equals(s: &[u8], pattern: &str) -> bool {
let mut xs = s.iter().map(|&c| match c {
b'A'..=b'Z' => c + 32,
_ => c,
});
let mut ys = pattern.as_bytes().iter().cloned();
loop {
match (xs.next(), ys.next()) {
(None, None) => return true,
(None, _) | (_, None) => return false,
(Some(x), Some(y)) if x != y => return false,
_ => (),
}
}
}

/// Tries to parse the non-negative number from `min` to `max` digits.
///
/// The absence of digits at all is an unconditional error.
Expand Down Expand Up @@ -143,14 +125,16 @@ pub(super) fn short_weekday(s: &str) -> ParseResult<(&str, Weekday)> {
/// It prefers long month names to short month names when both are possible.
pub(super) fn short_or_long_month0(s: &str) -> ParseResult<(&str, u8)> {
// lowercased month names, minus first three chars
static LONG_MONTH_SUFFIXES: [&str; 12] =
["uary", "ruary", "ch", "il", "", "e", "y", "ust", "tember", "ober", "ember", "ember"];
static LONG_MONTH_SUFFIXES: [&[u8]; 12] = [
b"uary", b"ruary", b"ch", b"il", b"", b"e", b"y", b"ust", b"tember", b"ober", b"ember",
b"ember",
];

let (mut s, month0) = short_month0(s)?;

// tries to consume the suffix if possible
let suffix = LONG_MONTH_SUFFIXES[month0 as usize];
if s.len() >= suffix.len() && equals(&s.as_bytes()[..suffix.len()], suffix) {
if s.len() >= suffix.len() && s.as_bytes()[..suffix.len()].eq_ignore_ascii_case(suffix) {
s = &s[suffix.len()..];
}

Expand All @@ -161,14 +145,14 @@ pub(super) fn short_or_long_month0(s: &str) -> ParseResult<(&str, u8)> {
/// It prefers long weekday names to short weekday names when both are possible.
pub(super) fn short_or_long_weekday(s: &str) -> ParseResult<(&str, Weekday)> {
// lowercased weekday names, minus first three chars
static LONG_WEEKDAY_SUFFIXES: [&str; 7] =
["day", "sday", "nesday", "rsday", "day", "urday", "day"];
static LONG_WEEKDAY_SUFFIXES: [&[u8]; 7] =
[b"day", b"sday", b"nesday", b"rsday", b"day", b"urday", b"day"];

let (mut s, weekday) = short_weekday(s)?;

// tries to consume the suffix if possible
let suffix = LONG_WEEKDAY_SUFFIXES[weekday.num_days_from_monday() as usize];
if s.len() >= suffix.len() && equals(&s.as_bytes()[..suffix.len()], suffix) {
if s.len() >= suffix.len() && s.as_bytes()[..suffix.len()].eq_ignore_ascii_case(suffix) {
s = &s[suffix.len()..];
}

Expand Down Expand Up @@ -201,17 +185,6 @@ pub(crate) fn colon_or_space(s: &str) -> ParseResult<&str> {
Ok(s.trim_start_matches(|c: char| c == ':' || c.is_whitespace()))
}

/// Tries to parse `[-+]\d\d` continued by `\d\d`. Return an offset in seconds if possible.
///
/// The additional `colon` may be used to parse a mandatory or optional `:`
/// between hours and minutes, and should return either a new suffix or `Err` when parsing fails.
pub(crate) fn timezone_offset<F>(s: &str, consume_colon: F) -> ParseResult<(&str, i32)>
where
F: FnMut(&str) -> ParseResult<&str>,
{
timezone_offset_internal(s, consume_colon, false, true)
}

/// Parse a timezone from `s` and return the offset in seconds.
///
/// The `consume_colon` function is used to parse a mandatory or optional `:`
Expand All @@ -226,15 +199,35 @@ where
/// This is part of [RFC 3339 & ISO 8601].
///
/// [RFC 3339 & ISO 8601]: https://en.wikipedia.org/w/index.php?title=ISO_8601&oldid=1114309368#Time_offsets_from_UTC
fn timezone_offset_internal<F>(
pub(crate) fn timezone_offset<F>(
mut s: &str,
mut consume_colon: F,
allow_zulu: bool,
allow_missing_minutes: bool,
allow_tz_minus_sign: bool,
) -> ParseResult<(&str, i32)>
where
F: FnMut(&str) -> ParseResult<&str>,
{
if allow_zulu {
let bytes = s.as_bytes();
match bytes.first() {
Some(&b'z') | Some(&b'Z') => return Ok((&s[1..], 0)),
Some(&b'u') | Some(&b'U') => {
if bytes.len() >= 3 {
let (b, c) = (bytes[1], bytes[2]);
match (b | 32, c | 32) {
(b't', b'c') => return Ok((&s[3..], 0)),
_ => return Err(INVALID),
}
} else {
return Err(INVALID);
}
}
_ => {}
}
}

const fn digits(s: &str) -> ParseResult<(u8, u8)> {
let b = s.as_bytes();
if b.len() < 2 {
Expand Down Expand Up @@ -302,41 +295,6 @@ where
Ok((s, if negative { -seconds } else { seconds }))
}

/// Same as `timezone_offset` but also allows for `z`/`Z` which is the same as `+00:00`.
pub(super) fn timezone_offset_zulu<F>(s: &str, colon: F) -> ParseResult<(&str, i32)>
where
F: FnMut(&str) -> ParseResult<&str>,
{
let bytes = s.as_bytes();
match bytes.first() {
Some(&b'z') | Some(&b'Z') => Ok((&s[1..], 0)),
Some(&b'u') | Some(&b'U') => {
if bytes.len() >= 3 {
let (b, c) = (bytes[1], bytes[2]);
match (b | 32, c | 32) {
(b't', b'c') => Ok((&s[3..], 0)),
_ => Err(INVALID),
}
} else {
Err(INVALID)
}
}
_ => timezone_offset(s, colon),
}
}

/// Same as `timezone_offset` but also allows for `z`/`Z` which is the same as
/// `+00:00`, and allows missing minutes entirely.
pub(super) fn timezone_offset_permissive<F>(s: &str, colon: F) -> ParseResult<(&str, i32)>
where
F: FnMut(&str) -> ParseResult<&str>,
{
match s.as_bytes().first() {
Some(&b'z') | Some(&b'Z') => Ok((&s[1..], 0)),
_ => timezone_offset_internal(s, colon, true, true),
}
}

/// Same as `timezone_offset` but also allows for RFC 2822 legacy timezones.
/// May return `None` which indicates an insufficient offset data (i.e. `-0000`).
/// See [RFC 2822 Section 4.3].
Expand All @@ -349,17 +307,17 @@ pub(super) fn timezone_offset_2822(s: &str) -> ParseResult<(&str, Option<i32>)>
let name = &s.as_bytes()[..upto];
let s = &s[upto..];
let offset_hours = |o| Ok((s, Some(o * 3600)));
if equals(name, "gmt") || equals(name, "ut") {
if name.eq_ignore_ascii_case(b"gmt") || name.eq_ignore_ascii_case(b"ut") {
offset_hours(0)
} else if equals(name, "edt") {
} else if name.eq_ignore_ascii_case(b"edt") {
offset_hours(-4)
} else if equals(name, "est") || equals(name, "cdt") {
} else if name.eq_ignore_ascii_case(b"est") || name.eq_ignore_ascii_case(b"cdt") {
offset_hours(-5)
} else if equals(name, "cst") || equals(name, "mdt") {
} else if name.eq_ignore_ascii_case(b"cst") || name.eq_ignore_ascii_case(b"mdt") {
offset_hours(-6)
} else if equals(name, "mst") || equals(name, "pdt") {
} else if name.eq_ignore_ascii_case(b"mst") || name.eq_ignore_ascii_case(b"pdt") {
offset_hours(-7)
} else if equals(name, "pst") {
} else if name.eq_ignore_ascii_case(b"pst") {
offset_hours(-8)
} else if name.len() == 1 {
match name[0] {
Expand All @@ -371,17 +329,11 @@ pub(super) fn timezone_offset_2822(s: &str) -> ParseResult<(&str, Option<i32>)>
Ok((s, None))
}
} else {
let (s_, offset) = timezone_offset_internal(s, |s| Ok(s), false, false)?;
let (s_, offset) = timezone_offset(s, |s| Ok(s), false, false, false)?;
Ok((s_, Some(offset)))
}
}

/// Tries to consume everything until next whitespace-like symbol.
/// Does not provide any offset information from the consumed data.
pub(super) fn timezone_name_skip(s: &str) -> ParseResult<(&str, ())> {
Ok((s.trim_start_matches(|c: char| !c.is_whitespace()), ()))
}

/// Tries to consume an RFC2822 comment including preceding ` `.
///
/// Returns the remaining string after the closing parenthesis.
Expand Down
9 changes: 3 additions & 6 deletions src/offset/fixed.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,13 +11,10 @@ use core::str::FromStr;
use rkyv::{Archive, Deserialize, Serialize};

use super::{LocalResult, Offset, TimeZone};
use crate::format::scan;
use crate::format::OUT_OF_RANGE;
use crate::format::{scan, OUT_OF_RANGE};
use crate::naive::{NaiveDate, NaiveDateTime, NaiveTime};
use crate::oldtime::Duration as OldDuration;
use crate::DateTime;
use crate::ParseError;
use crate::Timelike;
use crate::{DateTime, ParseError, Timelike};

/// The time zone with fixed offset, from UTC-23:59:59 to UTC+23:59:59.
///
Expand Down Expand Up @@ -121,7 +118,7 @@ impl FixedOffset {
impl FromStr for FixedOffset {
type Err = ParseError;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let (_, offset) = scan::timezone_offset(s, scan::colon_or_space)?;
let (_, offset) = scan::timezone_offset(s, scan::colon_or_space, false, false, true)?;
Self::east_opt(offset).ok_or(OUT_OF_RANGE)
}
}
Expand Down