1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242
//! Parser for format descriptions.
use alloc::boxed::Box;
use alloc::vec::Vec;
use crate::{error, format_description};
/// A helper macro to make version restrictions simpler to read and write.
macro_rules! version {
($range:expr) => {
$range.contains(&VERSION)
};
}
/// A helper macro to statically validate the version (when used as a const parameter).
macro_rules! validate_version {
($version:ident) => {
#[allow(clippy::let_unit_value)]
let _ = $crate::format_description::parse::Version::<$version>::IS_VALID;
};
}
mod ast;
mod format_item;
mod lexer;
/// A struct that is used to ensure that the version is valid.
struct Version<const N: usize>;
impl<const N: usize> Version<N> {
/// A constant that panics if the version is not valid. This results in a post-monomorphization
/// error.
const IS_VALID: () = assert!(N >= 1 && N <= 2);
}
/// Parse a sequence of items from the format description.
///
/// The syntax for the format description can be found in [the
/// book](https://time-rs.github.io/book/api/format-description.html).
///
/// This function exists for backward compatibility reasons. It is equivalent to calling
/// `parse_borrowed::<1>(s)`. In the future, this function will be deprecated in favor of
/// `parse_borrowed`.
pub fn parse(
s: &str,
) -> Result<Vec<format_description::BorrowedFormatItem<'_>>, error::InvalidFormatDescription> {
parse_borrowed::<1>(s)
}
/// Parse a sequence of items from the format description.
///
/// The syntax for the format description can be found in [the
/// book](https://time-rs.github.io/book/api/format-description.html). The version of the format
/// description is provided as the const parameter. **It is recommended to use version 2.**
pub fn parse_borrowed<const VERSION: usize>(
s: &str,
) -> Result<Vec<format_description::BorrowedFormatItem<'_>>, error::InvalidFormatDescription> {
validate_version!(VERSION);
let mut lexed = lexer::lex::<VERSION>(s.as_bytes());
let ast = ast::parse::<_, VERSION>(&mut lexed);
let format_items = format_item::parse(ast);
Ok(format_items
.map(|res| res.and_then(TryInto::try_into))
.collect::<Result<_, _>>()?)
}
/// Parse a sequence of items from the format description.
///
/// The syntax for the format description can be found in [the
/// book](https://time-rs.github.io/book/api/format-description.html). The version of the format
/// description is provided as the const parameter.
///
/// Unlike [`parse`], this function returns [`OwnedFormatItem`], which owns its contents. This means
/// that there is no lifetime that needs to be handled. **It is recommended to use version 2.**
///
/// [`OwnedFormatItem`]: crate::format_description::OwnedFormatItem
pub fn parse_owned<const VERSION: usize>(
s: &str,
) -> Result<format_description::OwnedFormatItem, error::InvalidFormatDescription> {
validate_version!(VERSION);
let mut lexed = lexer::lex::<VERSION>(s.as_bytes());
let ast = ast::parse::<_, VERSION>(&mut lexed);
let format_items = format_item::parse(ast);
let items = format_items.collect::<Result<Box<_>, _>>()?;
Ok(items.into())
}
/// A location within a string.
#[derive(Clone, Copy)]
struct Location {
/// The zero-indexed byte of the string.
byte: u32,
}
impl Location {
/// Create a new [`Span`] from `self` to `other`.
const fn to(self, end: Self) -> Span {
Span { start: self, end }
}
/// Offset the location by the provided amount.
///
/// Note that this assumes the resulting location is on the same line as the original location.
#[must_use = "this does not modify the original value"]
const fn offset(&self, offset: u32) -> Self {
Self {
byte: self.byte + offset,
}
}
/// Create an error with the provided message at this location.
const fn error(self, message: &'static str) -> ErrorInner {
ErrorInner {
_message: message,
_span: Span {
start: self,
end: self,
},
}
}
}
/// A start and end point within a string.
#[derive(Clone, Copy)]
struct Span {
#[allow(clippy::missing_docs_in_private_items)]
start: Location,
#[allow(clippy::missing_docs_in_private_items)]
end: Location,
}
impl Span {
/// Obtain a `Span` pointing at the start of the pre-existing span.
#[must_use = "this does not modify the original value"]
const fn shrink_to_start(&self) -> Self {
Self {
start: self.start,
end: self.start,
}
}
/// Obtain a `Span` pointing at the end of the pre-existing span.
#[must_use = "this does not modify the original value"]
const fn shrink_to_end(&self) -> Self {
Self {
start: self.end,
end: self.end,
}
}
/// Obtain a `Span` that ends before the provided position of the pre-existing span.
#[must_use = "this does not modify the original value"]
const fn shrink_to_before(&self, pos: u32) -> Self {
Self {
start: self.start,
end: Location {
byte: self.start.byte + pos - 1,
},
}
}
/// Obtain a `Span` that starts after provided position to the end of the pre-existing span.
#[must_use = "this does not modify the original value"]
const fn shrink_to_after(&self, pos: u32) -> Self {
Self {
start: Location {
byte: self.start.byte + pos + 1,
},
end: self.end,
}
}
/// Create an error with the provided message at this span.
const fn error(self, message: &'static str) -> ErrorInner {
ErrorInner {
_message: message,
_span: self,
}
}
}
/// A value with an associated [`Span`].
#[derive(Clone, Copy)]
struct Spanned<T> {
/// The value.
value: T,
/// Where the value was in the format string.
span: Span,
}
impl<T> core::ops::Deref for Spanned<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
&self.value
}
}
/// Helper trait to attach a [`Span`] to a value.
trait SpannedValue: Sized {
/// Attach a [`Span`] to a value.
fn spanned(self, span: Span) -> Spanned<Self>;
}
impl<T> SpannedValue for T {
fn spanned(self, span: Span) -> Spanned<Self> {
Spanned { value: self, span }
}
}
/// The internal error type.
struct ErrorInner {
/// The message displayed to the user.
_message: &'static str,
/// Where the error originated.
_span: Span,
}
/// A complete error description.
struct Error {
/// The internal error.
_inner: Unused<ErrorInner>,
/// The error needed for interoperability with the rest of `time`.
public: error::InvalidFormatDescription,
}
impl From<Error> for error::InvalidFormatDescription {
fn from(error: Error) -> Self {
error.public
}
}
/// A value that may be used in the future, but currently is not.
///
/// This struct exists so that data can semantically be passed around without _actually_ passing it
/// around. This way the data still exists if it is needed in the future.
// `PhantomData` is not used directly because we don't want to introduce any trait implementations.
struct Unused<T>(core::marker::PhantomData<T>);
/// Indicate that a value is currently unused.
fn unused<T>(_: T) -> Unused<T> {
Unused(core::marker::PhantomData)
}