use std::{fmt, ops::Range};
use crate::{
Buffer, ParseError,
err::{perr, ParseErrorKind::*},
escape::{scan_raw_string, unescape_string},
};
/// A byte string or raw byte string literal, e.g. `b"hello"` or `br#"abc"def"#`.
///
/// See [the reference][ref] for more information.
///
/// [ref]:
https://doc.rust-lang.org/reference/tokens.html#byte-string-literals
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct ByteStringLit<B: Buffer> {
/// The raw input.
raw: B,
/// The string value (with all escaped unescaped), or `None` if there were
/// no escapes. In the latter case, `input` is the string value.
value: Option<Vec<u8>>,
/// 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> ByteStringLit<B> {
/// Parses the input as a (raw) byte 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> {
if input.is_empty() {
return Err(perr(None, Empty));
}
if !input.starts_with(r#"b""#) && !input.starts_with("br") {
return Err(perr(None, InvalidByteStringLiteralStart));
}
let (value, num_hashes, start_suffix) = parse_impl(&input)?;
Ok(Self { raw: input, value, num_hashes, start_suffix })
}
/// Returns the string value this literal represents (where all escapes have
/// been turned into their respective values).
pub fn value(&self) -> &[u8] {
self.value.as_deref().unwrap_or(&self.raw.as_bytes()[self.inner_range()])
}
/// Like `value` but returns a potentially owned version of the value.
///
/// The return value is either `Cow<'static, [u8]>` if `B = String`, or
/// `Cow<'a, [u8]>` if `B = &'a str`.
pub fn into_value(self) -> B::ByteCow {
let inner_range = self.inner_range();
let Self { raw, value, .. } = self;
value.map(B::ByteCow::from).unwrap_or_else(|| raw.cut(inner_range).into_byte_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_byte_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 => 2..self.start_suffix - 1,
Some(n) => 2 + n as usize + 1..self.start_suffix - n as usize - 1,
}
}
}
impl ByteStringLit<&str> {
/// Makes a copy of the underlying buffer and returns the owned version of
/// `Self`.
pub fn into_owned(self) -> ByteStringLit<String> {
ByteStringLit {
raw: self.raw.to_owned(),
value: self.value,
num_hashes: self.num_hashes,
start_suffix: self.start_suffix,
}
}
}
impl<B: Buffer> fmt::Display for ByteStringLit<B> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.pad(&self.raw)
}
}
/// Precondition: input has to start with either `b"` or `br`.
#[inline(never)]
fn parse_impl(input: &str) -> Result<(Option<Vec<u8>>, Option<u32>, usize), ParseError> {
if input.starts_with("br") {
scan_raw_string::<u8>(&input, 2)
.map(|(v, num, start_suffix)| (v.map(String::into_bytes), Some(num), start_suffix))
} else {
unescape_string::<u8>(&input, 2)
.map(|(v, start_suffix)| (v.map(String::into_bytes), None, start_suffix))
}
}
#[cfg(test)]
mod tests;
