1 files changed, 187 insertions, 0 deletions
diff --git a/third_party/rust/unicode-normalization/src/quick_check.rs b/third_party/rust/unicode-normalization/src/quick_check.rs
new file mode 100644
index 0000000000..4507b2abb4
--- /dev/null
+++ b/third_party/rust/unicode-normalization/src/quick_check.rs
@@ -0,0 +1,187 @@
+use crate::lookups::canonical_combining_class;
+use crate::stream_safe;
+use crate::tables;
+use crate::UnicodeNormalization;
+
+/// The QuickCheck algorithm can quickly determine if a text is or isn't
+/// normalized without any allocations in many cases, but it has to be able to
+/// return `Maybe` when a full decomposition and recomposition is necessary.
+#[derive(Debug, Eq, PartialEq)]
+pub enum IsNormalized {
+    /// The text is definitely normalized.
+    Yes,
+    /// The text is definitely not normalized.
+    No,
+    /// The text may be normalized.
+    Maybe,
+}
+
+// https://unicode.org/reports/tr15/#Detecting_Normalization_Forms
+#[inline]
+fn quick_check<F, I>(s: I, is_allowed: F, stream_safe: bool) -> IsNormalized
+where
+    I: Iterator<Item = char>,
+    F: Fn(char) -> IsNormalized,
+{
+    let mut last_cc = 0u8;
+    let mut nonstarter_count = 0;
+    let mut result = IsNormalized::Yes;
+    for ch in s {
+        // For ASCII we know it's always allowed and a starter
+        if ch <= '\x7f' {
+            last_cc = 0;
+            nonstarter_count = 0;
+            continue;
+        }
+
+        // Otherwise, lookup the combining class and QC property
+        let cc = canonical_combining_class(ch);
+        if last_cc > cc && cc != 0 {
+            return IsNormalized::No;
+        }
+        match is_allowed(ch) {
+            IsNormalized::Yes => (),
+            IsNormalized::No => return IsNormalized::No,
+            IsNormalized::Maybe => {
+                result = IsNormalized::Maybe;
+            }
+        }
+        if stream_safe {
+            let decomp = stream_safe::classify_nonstarters(ch);
+
+            // If we're above `MAX_NONSTARTERS`, we're definitely *not*
+            // stream-safe normalized.
+            if nonstarter_count + decomp.leading_nonstarters > stream_safe::MAX_NONSTARTERS {
+                return IsNormalized::No;
+            }
+            if decomp.leading_nonstarters == decomp.decomposition_len {
+                nonstarter_count += decomp.decomposition_len;
+            } else {
+                nonstarter_count = decomp.trailing_nonstarters;
+            }
+        }
+        last_cc = cc;
+    }
+    result
+}
+
+/// Quickly check if a string is in NFC, potentially returning
+/// `IsNormalized::Maybe` if further checks are necessary.  In this case a check
+/// like `s.chars().nfc().eq(s.chars())` should suffice.
+#[inline]
+pub fn is_nfc_quick<I: Iterator<Item = char>>(s: I) -> IsNormalized {
+    quick_check(s, tables::qc_nfc, false)
+}
+
+/// Quickly check if a string is in NFKC.
+#[inline]
+pub fn is_nfkc_quick<I: Iterator<Item = char>>(s: I) -> IsNormalized {
+    quick_check(s, tables::qc_nfkc, false)
+}
+
+/// Quickly check if a string is in NFD.
+#[inline]
+pub fn is_nfd_quick<I: Iterator<Item = char>>(s: I) -> IsNormalized {
+    quick_check(s, tables::qc_nfd, false)
+}
+
+/// Quickly check if a string is in NFKD.
+#[inline]
+pub fn is_nfkd_quick<I: Iterator<Item = char>>(s: I) -> IsNormalized {
+    quick_check(s, tables::qc_nfkd, false)
+}
+
+/// Quickly check if a string is Stream-Safe NFC.
+#[inline]
+pub fn is_nfc_stream_safe_quick<I: Iterator<Item = char>>(s: I) -> IsNormalized {
+    quick_check(s, tables::qc_nfc, true)
+}
+
+/// Quickly check if a string is Stream-Safe NFD.
+#[inline]
+pub fn is_nfd_stream_safe_quick<I: Iterator<Item = char>>(s: I) -> IsNormalized {
+    quick_check(s, tables::qc_nfd, true)
+}
+
+/// Authoritatively check if a string is in NFC.
+#[inline]
+pub fn is_nfc(s: &str) -> bool {
+    match is_nfc_quick(s.chars()) {
+        IsNormalized::Yes => true,
+        IsNormalized::No => false,
+        IsNormalized::Maybe => s.chars().eq(s.chars().nfc()),
+    }
+}
+
+/// Authoritatively check if a string is in NFKC.
+#[inline]
+pub fn is_nfkc(s: &str) -> bool {
+    match is_nfkc_quick(s.chars()) {
+        IsNormalized::Yes => true,
+        IsNormalized::No => false,
+        IsNormalized::Maybe => s.chars().eq(s.chars().nfkc()),
+    }
+}
+
+/// Authoritatively check if a string is in NFD.
+#[inline]
+pub fn is_nfd(s: &str) -> bool {
+    match is_nfd_quick(s.chars()) {
+        IsNormalized::Yes => true,
+        IsNormalized::No => false,
+        IsNormalized::Maybe => s.chars().eq(s.chars().nfd()),
+    }
+}
+
+/// Authoritatively check if a string is in NFKD.
+#[inline]
+pub fn is_nfkd(s: &str) -> bool {
+    match is_nfkd_quick(s.chars()) {
+        IsNormalized::Yes => true,
+        IsNormalized::No => false,
+        IsNormalized::Maybe => s.chars().eq(s.chars().nfkd()),
+    }
+}
+
+/// Authoritatively check if a string is Stream-Safe NFC.
+#[inline]
+pub fn is_nfc_stream_safe(s: &str) -> bool {
+    match is_nfc_stream_safe_quick(s.chars()) {
+        IsNormalized::Yes => true,
+        IsNormalized::No => false,
+        IsNormalized::Maybe => s.chars().eq(s.chars().stream_safe().nfc()),
+    }
+}
+
+/// Authoritatively check if a string is Stream-Safe NFD.
+#[inline]
+pub fn is_nfd_stream_safe(s: &str) -> bool {
+    match is_nfd_stream_safe_quick(s.chars()) {
+        IsNormalized::Yes => true,
+        IsNormalized::No => false,
+        IsNormalized::Maybe => s.chars().eq(s.chars().stream_safe().nfd()),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{is_nfc_stream_safe_quick, is_nfd_stream_safe_quick, IsNormalized};
+
+    #[test]
+    fn test_stream_safe_nfd() {
+        let okay = "Da\u{031b}\u{0316}\u{0317}\u{0318}\u{0319}\u{031c}\u{031d}\u{0300}\u{0301}\u{0302}\u{0303}\u{0304}\u{0305}\u{0306}\u{0307}\u{0308}\u{0309}\u{030a}\u{030b}\u{030c}\u{030d}\u{030e}\u{030f}\u{0310}\u{0311}\u{0312}\u{0313}\u{0314}\u{0315}\u{031a}ngerzone";
+        assert_eq!(is_nfd_stream_safe_quick(okay.chars()), IsNormalized::Yes);
+
+        let too_much = "Da\u{031b}\u{0316}\u{0317}\u{0318}\u{0319}\u{031c}\u{031d}\u{031e}\u{0300}\u{0301}\u{0302}\u{0303}\u{0304}\u{0305}\u{0306}\u{0307}\u{0308}\u{0309}\u{030a}\u{030b}\u{030c}\u{030d}\u{030e}\u{030f}\u{0310}\u{0311}\u{0312}\u{0313}\u{0314}\u{0315}\u{031a}ngerzone";
+        assert_eq!(is_nfd_stream_safe_quick(too_much.chars()), IsNormalized::No);
+    }
+
+    #[test]
+    fn test_stream_safe_nfc() {
+        let okay = "ok\u{e0}\u{031b}\u{0316}\u{0317}\u{0318}\u{0319}\u{031c}\u{031d}\u{0301}\u{0302}\u{0303}\u{0304}\u{0305}\u{0306}\u{0307}\u{0308}\u{0309}\u{030a}\u{030b}\u{030c}\u{030d}\u{030e}\u{030f}\u{0310}\u{0311}\u{0312}\u{0313}\u{0314}\u{0315}\u{031a}y";
+        assert_eq!(is_nfc_stream_safe_quick(okay.chars()), IsNormalized::Maybe);
+
+        let too_much = "not ok\u{e0}\u{031b}\u{0316}\u{0317}\u{0318}\u{0319}\u{031c}\u{031d}\u{031e}\u{0301}\u{0302}\u{0303}\u{0304}\u{0305}\u{0306}\u{0307}\u{0308}\u{0309}\u{030a}\u{030b}\u{030c}\u{030d}\u{030e}\u{030f}\u{0310}\u{0311}\u{0312}\u{0313}\u{0314}\u{0315}\u{031a}y";
+        assert_eq!(is_nfc_stream_safe_quick(too_much.chars()), IsNormalized::No);
+    }
+}