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|
//! Parser for format descriptions.
use alloc::vec::Vec;
use core::ops::{RangeFrom, RangeTo};
mod ast;
mod format_item;
mod lexer;
/// 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).
pub fn parse(
s: &str,
) -> Result<Vec<crate::format_description::FormatItem<'_>>, crate::error::InvalidFormatDescription>
{
let lexed = lexer::lex(s.as_bytes());
let ast = ast::parse(lexed);
let format_items = format_item::parse(ast);
Ok(format_items
.map(|res| res.map(Into::into))
.collect::<Result<Vec<_>, _>>()?)
}
/// 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).
///
/// Unlike [`parse`], this function returns [`OwnedFormatItem`], which owns its contents. This means
/// that there is no lifetime that needs to be handled.
///
/// [`OwnedFormatItem`]: crate::format_description::OwnedFormatItem
pub fn parse_owned(
s: &str,
) -> Result<crate::format_description::OwnedFormatItem, crate::error::InvalidFormatDescription> {
let lexed = lexer::lex(s.as_bytes());
let ast = ast::parse(lexed);
let format_items = format_item::parse(ast);
let items = format_items
.map(|res| res.map(Into::into))
.collect::<Result<Vec<_>, _>>()?
.into_boxed_slice();
Ok(crate::format_description::OwnedFormatItem::Compound(items))
}
/// A location within a string.
#[derive(Clone, Copy)]
struct Location {
/// The one-indexed line of the string.
line: usize,
/// The one-indexed column of the string.
column: usize,
/// The zero-indexed byte of the string.
byte: usize,
}
impl Location {
/// 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: usize) -> Self {
Self {
line: self.line,
column: self.column + offset,
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 {
/// Create a new `Span` from the provided start and end locations.
const fn start_end(start: Location, end: Location) -> Self {
Self { start, end }
}
/// Reduce this span to the provided range.
#[must_use = "this does not modify the original value"]
fn subspan(&self, range: impl Subspan) -> Self {
range.subspan(self)
}
/// 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,
}
}
/// Create an error with the provided message at this span.
const fn error(self, message: &'static str) -> ErrorInner {
ErrorInner {
_message: message,
_span: self,
}
}
/// Get the byte index that the span starts at.
const fn start_byte(&self) -> usize {
self.start.byte
}
}
/// A trait for types that can be used to reduce a `Span`.
trait Subspan {
/// Reduce the provided `Span` to a new `Span`.
fn subspan(self, span: &Span) -> Span;
}
impl Subspan for RangeFrom<usize> {
fn subspan(self, span: &Span) -> Span {
assert_eq!(span.start.line, span.end.line);
Span {
start: Location {
line: span.start.line,
column: span.start.column + self.start,
byte: span.start.byte + self.start,
},
end: span.end,
}
}
}
impl Subspan for RangeTo<usize> {
fn subspan(self, span: &Span) -> Span {
assert_eq!(span.start.line, span.end.line);
Span {
start: span.start,
end: Location {
line: span.start.line,
column: span.start.column + self.end - 1,
byte: span.start.byte + self.end - 1,
},
}
}
}
/// 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: ErrorInner,
/// The error needed for interoperability with the rest of `time`.
public: crate::error::InvalidFormatDescription,
}
impl From<Error> for crate::error::InvalidFormatDescription {
fn from(error: Error) -> Self {
error.public
}
}
|
