1 files changed, 159 insertions, 0 deletions
diff --git a/vendor/potential_utf/src/writeable.rs b/vendor/potential_utf/src/writeable.rs
new file mode 100644
index 00000000..cd489914
--- /dev/null
+++ b/vendor/potential_utf/src/writeable.rs
@@ -0,0 +1,159 @@
+// This file is part of ICU4X. For terms of use, please see the file
+// called LICENSE at the top level of the ICU4X source tree
+// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
+
+use crate::{PotentialUtf16, PotentialUtf8};
+use alloc::borrow::Cow;
+use core::fmt::Write;
+use writeable::{LengthHint, Part, PartsWrite, TryWriteable};
+
+use core::{char::DecodeUtf16Error, fmt, str::Utf8Error};
+
+/// This impl requires enabling the optional `writeable` Cargo feature
+impl TryWriteable for &'_ PotentialUtf8 {
+    type Error = Utf8Error;
+
+    fn try_write_to_parts<S: PartsWrite + ?Sized>(
+        &self,
+        sink: &mut S,
+    ) -> Result<Result<(), Self::Error>, fmt::Error> {
+        let mut remaining = &self.0;
+        let mut r = Ok(());
+        loop {
+            match core::str::from_utf8(remaining) {
+                Ok(valid) => {
+                    sink.write_str(valid)?;
+                    return Ok(r);
+                }
+                Err(e) => {
+                    // SAFETY: By Utf8Error invariants
+                    let valid = unsafe {
+                        core::str::from_utf8_unchecked(remaining.get_unchecked(..e.valid_up_to()))
+                    };
+                    sink.write_str(valid)?;
+                    sink.with_part(Part::ERROR, |s| s.write_char(char::REPLACEMENT_CHARACTER))?;
+                    if r.is_ok() {
+                        r = Err(e);
+                    }
+                    let Some(error_len) = e.error_len() else {
+                        return Ok(r); // end of string
+                    };
+                    // SAFETY: By Utf8Error invariants
+                    remaining = unsafe { remaining.get_unchecked(e.valid_up_to() + error_len..) }
+                }
+            }
+        }
+    }
+
+    fn writeable_length_hint(&self) -> LengthHint {
+        // Lower bound is all valid UTF-8, upper bound is all bytes with the high bit, which become replacement characters.
+        LengthHint::between(self.0.len(), self.0.len() * 3)
+    }
+
+    fn try_write_to_string(&self) -> Result<Cow<str>, (Self::Error, Cow<str>)> {
+        match core::str::from_utf8(&self.0) {
+            Ok(valid) => Ok(Cow::Borrowed(valid)),
+            Err(e) => {
+                // SAFETY: By Utf8Error invariants
+                let valid = unsafe {
+                    core::str::from_utf8_unchecked(self.0.get_unchecked(..e.valid_up_to()))
+                };
+
+                // Let's assume this is the only error
+                let mut out = alloc::string::String::with_capacity(
+                    self.0.len() + char::REPLACEMENT_CHARACTER.len_utf8()
+                        - e.error_len().unwrap_or(0),
+                );
+
+                out.push_str(valid);
+                out.push(char::REPLACEMENT_CHARACTER);
+
+                // If there's more, we can use `try_write_to`
+                if let Some(error_len) = e.error_len() {
+                    // SAFETY: By Utf8Error invariants
+                    let remaining = unsafe { self.0.get_unchecked(e.valid_up_to() + error_len..) };
+                    let _discard = PotentialUtf8::from_bytes(remaining).try_write_to(&mut out);
+                }
+
+                Err((e, Cow::Owned(out)))
+            }
+        }
+    }
+}
+
+/// This impl requires enabling the optional `writeable` Cargo feature
+impl TryWriteable for &'_ PotentialUtf16 {
+    type Error = DecodeUtf16Error;
+
+    fn try_write_to_parts<S: PartsWrite + ?Sized>(
+        &self,
+        sink: &mut S,
+    ) -> Result<Result<(), Self::Error>, fmt::Error> {
+        let mut r = Ok(());
+        for c in core::char::decode_utf16(self.0.iter().copied()) {
+            match c {
+                Ok(c) => sink.write_char(c)?,
+                Err(e) => {
+                    if r.is_ok() {
+                        r = Err(e);
+                    }
+                    sink.with_part(Part::ERROR, |s| s.write_char(char::REPLACEMENT_CHARACTER))?;
+                }
+            }
+        }
+        Ok(r)
+    }
+
+    fn writeable_length_hint(&self) -> LengthHint {
+        // Lower bound is all ASCII, upper bound is all 3-byte code points (including replacement character)
+        LengthHint::between(self.0.len(), self.0.len() * 3)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    #![allow(invalid_from_utf8)] // only way to construct the error
+    use super::*;
+    use writeable::assert_try_writeable_parts_eq;
+
+    #[test]
+    fn test_utf8() {
+        assert_try_writeable_parts_eq!(
+            PotentialUtf8::from_bytes(b"Foo Bar"),
+            "Foo Bar",
+            Ok(()),
+            []
+        );
+        assert_try_writeable_parts_eq!(
+            PotentialUtf8::from_bytes(b"Foo\xFDBar"),
+            "Foo�Bar",
+            Err(core::str::from_utf8(b"Foo\xFDBar").unwrap_err()),
+            [(3, 6, Part::ERROR)]
+        );
+        assert_try_writeable_parts_eq!(
+            PotentialUtf8::from_bytes(b"Foo\xFDBar\xff"),
+            "Foo�Bar�",
+            Err(core::str::from_utf8(b"Foo\xFDBar\xff").unwrap_err()),
+            [(3, 6, Part::ERROR), (9, 12, Part::ERROR)],
+        );
+    }
+
+    #[test]
+    fn test_utf16() {
+        assert_try_writeable_parts_eq!(
+            PotentialUtf16::from_slice(&[0xD83E, 0xDD73]),
+            "🥳",
+            Ok(()),
+            []
+        );
+        assert_try_writeable_parts_eq!(
+            PotentialUtf16::from_slice(&[0xD83E, 0x20, 0xDD73]),
+            "� �",
+            Err(core::char::decode_utf16([0xD83E].into_iter())
+                .next()
+                .unwrap()
+                .unwrap_err()),
+            [(0, 3, Part::ERROR), (4, 7, Part::ERROR)]
+        );
+    }
+}