1 files changed, 126 insertions, 0 deletions
diff --git a/third_party/rust/litrs/src/bytestr/mod.rs b/third_party/rust/litrs/src/bytestr/mod.rs
new file mode 100644
index 0000000000..a0e09727f4
--- /dev/null
+++ b/third_party/rust/litrs/src/bytestr/mod.rs
@@ -0,0 +1,126 @@
+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;