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use std::{fmt, ops::Range};
use crate::{
Buffer, ParseError,
err::{perr, ParseErrorKind::*},
escape::{scan_raw_string, unescape_string},
parse::first_byte_or_empty,
};
/// A string or raw string literal, e.g. `"foo"`, `"Grüße"` or `r#"a🦊c"d🦀f"#`.
///
/// See [the reference][ref] for more information.
///
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct StringLit<B: Buffer> {
/// The raw input.
raw: B,
/// The string value (with all escapes unescaped), or `None` if there were
/// no escapes. In the latter case, the string value is in `raw`.
value: Option<String>,
/// The number of hash signs in case of a raw string literal, or `None` if
/// it's not a raw string literal.
num_hashes: Option<u32>,
/// Start index of the suffix or `raw.len()` if there is no suffix.
start_suffix: usize,
}
impl<B: Buffer> StringLit<B> {
/// Parses the input as a (raw) string literal. Returns an error if the
/// input is invalid or represents a different kind of literal.
pub fn parse(input: B) -> Result<Self, ParseError> {
match first_byte_or_empty(&input)? {
b'r' | b'"' => {
let (value, num_hashes, start_suffix) = parse_impl(&input)?;
Ok(Self { raw: input, value, num_hashes, start_suffix })
}
_ => Err(perr(0, InvalidStringLiteralStart)),
}
}
/// Returns the string value this literal represents (where all escapes have
/// been turned into their respective values).
pub fn value(&self) -> &str {
self.value.as_deref().unwrap_or(&self.raw[self.inner_range()])
}
/// Like `value` but returns a potentially owned version of the value.
///
/// The return value is either `Cow<'static, str>` if `B = String`, or
/// `Cow<'a, str>` if `B = &'a str`.
pub fn into_value(self) -> B::Cow {
let inner_range = self.inner_range();
let Self { raw, value, .. } = self;
value.map(B::Cow::from).unwrap_or_else(|| raw.cut(inner_range).into_cow())
}
/// The optional suffix. Returns `""` if the suffix is empty/does not exist.
pub fn suffix(&self) -> &str {
&(*self.raw)[self.start_suffix..]
}
/// Returns whether this literal is a raw string literal (starting with
/// `r`).
pub fn is_raw_string(&self) -> bool {
self.num_hashes.is_some()
}
/// Returns the raw input that was passed to `parse`.
pub fn raw_input(&self) -> &str {
&self.raw
}
/// Returns the raw input that was passed to `parse`, potentially owned.
pub fn into_raw_input(self) -> B {
self.raw
}
/// The range within `self.raw` that excludes the quotes and potential `r#`.
fn inner_range(&self) -> Range<usize> {
match self.num_hashes {
None => 1..self.start_suffix - 1,
Some(n) => 1 + n as usize + 1..self.start_suffix - n as usize - 1,
}
}
}
impl StringLit<&str> {
/// Makes a copy of the underlying buffer and returns the owned version of
/// `Self`.
pub fn into_owned(self) -> StringLit<String> {
StringLit {
raw: self.raw.to_owned(),
value: self.value,
num_hashes: self.num_hashes,
start_suffix: self.start_suffix,
}
}
}
impl<B: Buffer> fmt::Display for StringLit<B> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.pad(&self.raw)
}
}
/// Precondition: input has to start with either `"` or `r`.
#[inline(never)]
pub(crate) fn parse_impl(input: &str) -> Result<(Option<String>, Option<u32>, usize), ParseError> {
if input.starts_with('r') {
scan_raw_string::<char>(&input, 1)
.map(|(v, hashes, start_suffix)| (v, Some(hashes), start_suffix))
} else {
unescape_string::<char>(&input, 1)
.map(|(v, start_suffix)| (v, None, start_suffix))
}
}
#[cfg(test)]
mod tests;