1 files changed, 154 insertions, 0 deletions
diff --git a/third_party/rust/unicode-normalization/src/recompose.rs b/third_party/rust/unicode-normalization/src/recompose.rs
new file mode 100644
index 0000000000..2a1960afc8
--- /dev/null
+++ b/third_party/rust/unicode-normalization/src/recompose.rs
@@ -0,0 +1,154 @@
+// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use crate::decompose::Decompositions;
+use core::fmt::{self, Write};
+use tinyvec::TinyVec;
+
+#[derive(Clone)]
+enum RecompositionState {
+    Composing,
+    Purging(usize),
+    Finished(usize),
+}
+
+/// External iterator for a string recomposition's characters.
+#[derive(Clone)]
+pub struct Recompositions<I> {
+    iter: Decompositions<I>,
+    state: RecompositionState,
+    buffer: TinyVec<[char; 4]>,
+    composee: Option<char>,
+    last_ccc: Option<u8>,
+}
+
+#[inline]
+pub fn new_canonical<I: Iterator<Item = char>>(iter: I) -> Recompositions<I> {
+    Recompositions {
+        iter: super::decompose::new_canonical(iter),
+        state: self::RecompositionState::Composing,
+        buffer: TinyVec::new(),
+        composee: None,
+        last_ccc: None,
+    }
+}
+
+#[inline]
+pub fn new_compatible<I: Iterator<Item = char>>(iter: I) -> Recompositions<I> {
+    Recompositions {
+        iter: super::decompose::new_compatible(iter),
+        state: self::RecompositionState::Composing,
+        buffer: TinyVec::new(),
+        composee: None,
+        last_ccc: None,
+    }
+}
+
+impl<I: Iterator<Item = char>> Iterator for Recompositions<I> {
+    type Item = char;
+
+    #[inline]
+    fn next(&mut self) -> Option<char> {
+        use self::RecompositionState::*;
+
+        loop {
+            match self.state {
+                Composing => {
+                    for ch in self.iter.by_ref() {
+                        let ch_class = super::char::canonical_combining_class(ch);
+                        let k = match self.composee {
+                            None => {
+                                if ch_class != 0 {
+                                    return Some(ch);
+                                }
+                                self.composee = Some(ch);
+                                continue;
+                            }
+                            Some(k) => k,
+                        };
+                        match self.last_ccc {
+                            None => match super::char::compose(k, ch) {
+                                Some(r) => {
+                                    self.composee = Some(r);
+                                    continue;
+                                }
+                                None => {
+                                    if ch_class == 0 {
+                                        self.composee = Some(ch);
+                                        return Some(k);
+                                    }
+                                    self.buffer.push(ch);
+                                    self.last_ccc = Some(ch_class);
+                                }
+                            },
+                            Some(l_class) => {
+                                if l_class >= ch_class {
+                                    // `ch` is blocked from `composee`
+                                    if ch_class == 0 {
+                                        self.composee = Some(ch);
+                                        self.last_ccc = None;
+                                        self.state = Purging(0);
+                                        return Some(k);
+                                    }
+                                    self.buffer.push(ch);
+                                    self.last_ccc = Some(ch_class);
+                                    continue;
+                                }
+                                match super::char::compose(k, ch) {
+                                    Some(r) => {
+                                        self.composee = Some(r);
+                                        continue;
+                                    }
+                                    None => {
+                                        self.buffer.push(ch);
+                                        self.last_ccc = Some(ch_class);
+                                    }
+                                }
+                            }
+                        }
+                    }
+                    self.state = Finished(0);
+                    if self.composee.is_some() {
+                        return self.composee.take();
+                    }
+                }
+                Purging(next) => match self.buffer.get(next).cloned() {
+                    None => {
+                        self.buffer.clear();
+                        self.state = Composing;
+                    }
+                    s => {
+                        self.state = Purging(next + 1);
+                        return s;
+                    }
+                },
+                Finished(next) => match self.buffer.get(next).cloned() {
+                    None => {
+                        self.buffer.clear();
+                        return self.composee.take();
+                    }
+                    s => {
+                        self.state = Finished(next + 1);
+                        return s;
+                    }
+                },
+            }
+        }
+    }
+}
+
+impl<I: Iterator<Item = char> + Clone> fmt::Display for Recompositions<I> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        for c in self.clone() {
+            f.write_char(c)?;
+        }
+        Ok(())
+    }
+}