1 files changed, 271 insertions, 0 deletions
diff --git a/vendor/regex-automata/src/classes.rs b/vendor/regex-automata/src/classes.rs
new file mode 100644
index 000000000..143908b3a
--- /dev/null
+++ b/vendor/regex-automata/src/classes.rs
@@ -0,0 +1,271 @@
+use core::fmt;
+
+/// A representation of byte oriented equivalence classes.
+///
+/// This is used in a DFA to reduce the size of the transition table. This can
+/// have a particularly large impact not only on the total size of a dense DFA,
+/// but also on compile times.
+#[derive(Clone, Copy)]
+pub struct ByteClasses([u8; 256]);
+
+impl ByteClasses {
+    /// Creates a new set of equivalence classes where all bytes are mapped to
+    /// the same class.
+    pub fn empty() -> ByteClasses {
+        ByteClasses([0; 256])
+    }
+
+    /// Creates a new set of equivalence classes where each byte belongs to
+    /// its own equivalence class.
+    pub fn singletons() -> ByteClasses {
+        let mut classes = ByteClasses::empty();
+        for i in 0..256 {
+            classes.set(i as u8, i as u8);
+        }
+        classes
+    }
+
+    /// Copies the byte classes given. The given slice must have length 0 or
+    /// length 256. Slices of length 0 are treated as singletons (every byte
+    /// is its own class).
+    pub fn from_slice(slice: &[u8]) -> ByteClasses {
+        assert!(slice.is_empty() || slice.len() == 256);
+
+        if slice.is_empty() {
+            ByteClasses::singletons()
+        } else {
+            let mut classes = ByteClasses::empty();
+            for (b, &class) in slice.iter().enumerate() {
+                classes.set(b as u8, class);
+            }
+            classes
+        }
+    }
+
+    /// Set the equivalence class for the given byte.
+    #[inline]
+    pub fn set(&mut self, byte: u8, class: u8) {
+        self.0[byte as usize] = class;
+    }
+
+    /// Get the equivalence class for the given byte.
+    #[inline]
+    pub fn get(&self, byte: u8) -> u8 {
+        self.0[byte as usize]
+    }
+
+    /// Get the equivalence class for the given byte while forcefully
+    /// eliding bounds checks.
+    #[inline]
+    pub unsafe fn get_unchecked(&self, byte: u8) -> u8 {
+        *self.0.get_unchecked(byte as usize)
+    }
+
+    /// Return the total number of elements in the alphabet represented by
+    /// these equivalence classes. Equivalently, this returns the total number
+    /// of equivalence classes.
+    #[inline]
+    pub fn alphabet_len(&self) -> usize {
+        self.0[255] as usize + 1
+    }
+
+    /// Returns true if and only if every byte in this class maps to its own
+    /// equivalence class. Equivalently, there are 256 equivalence classes
+    /// and each class contains exactly one byte.
+    #[inline]
+    pub fn is_singleton(&self) -> bool {
+        self.alphabet_len() == 256
+    }
+
+    /// Returns an iterator over a sequence of representative bytes from each
+    /// equivalence class. Namely, this yields exactly N items, where N is
+    /// equivalent to the number of equivalence classes. Each item is an
+    /// arbitrary byte drawn from each equivalence class.
+    ///
+    /// This is useful when one is determinizing an NFA and the NFA's alphabet
+    /// hasn't been converted to equivalence classes yet. Picking an arbitrary
+    /// byte from each equivalence class then permits a full exploration of
+    /// the NFA instead of using every possible byte value.
+    #[cfg(feature = "std")]
+    pub fn representatives(&self) -> ByteClassRepresentatives {
+        ByteClassRepresentatives { classes: self, byte: 0, last_class: None }
+    }
+
+    /// Returns all of the bytes in the given equivalence class.
+    ///
+    /// The second element in the tuple indicates the number of elements in
+    /// the array.
+    fn elements(&self, equiv: u8) -> ([u8; 256], usize) {
+        let (mut array, mut len) = ([0; 256], 0);
+        for b in 0..256 {
+            if self.get(b as u8) == equiv {
+                array[len] = b as u8;
+                len += 1;
+            }
+        }
+        (array, len)
+    }
+}
+
+impl fmt::Debug for ByteClasses {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        if self.is_singleton() {
+            write!(f, "ByteClasses({{singletons}})")
+        } else {
+            write!(f, "ByteClasses(")?;
+            for equiv in 0..self.alphabet_len() {
+                let (members, len) = self.elements(equiv as u8);
+                write!(f, "{} => {:?}", equiv, &members[..len])?;
+            }
+            write!(f, ")")
+        }
+    }
+}
+
+/// An iterator over representative bytes from each equivalence class.
+#[cfg(feature = "std")]
+#[derive(Debug)]
+pub struct ByteClassRepresentatives<'a> {
+    classes: &'a ByteClasses,
+    byte: usize,
+    last_class: Option<u8>,
+}
+
+#[cfg(feature = "std")]
+impl<'a> Iterator for ByteClassRepresentatives<'a> {
+    type Item = u8;
+
+    fn next(&mut self) -> Option<u8> {
+        while self.byte < 256 {
+            let byte = self.byte as u8;
+            let class = self.classes.get(byte);
+            self.byte += 1;
+
+            if self.last_class != Some(class) {
+                self.last_class = Some(class);
+                return Some(byte);
+            }
+        }
+        None
+    }
+}
+
+/// A byte class set keeps track of an *approximation* of equivalence classes
+/// of bytes during NFA construction. That is, every byte in an equivalence
+/// class cannot discriminate between a match and a non-match.
+///
+/// For example, in the regex `[ab]+`, the bytes `a` and `b` would be in the
+/// same equivalence class because it never matters whether an `a` or a `b` is
+/// seen, and no combination of `a`s and `b`s in the text can discriminate
+/// a match.
+///
+/// Note though that this does not compute the minimal set of equivalence
+/// classes. For example, in the regex `[ac]+`, both `a` and `c` are in the
+/// same equivalence class for the same reason that `a` and `b` are in the
+/// same equivalence class in the aforementioned regex. However, in this
+/// implementation, `a` and `c` are put into distinct equivalence classes.
+/// The reason for this is implementation complexity. In the future, we should
+/// endeavor to compute the minimal equivalence classes since they can have a
+/// rather large impact on the size of the DFA.
+///
+/// The representation here is 256 booleans, all initially set to false. Each
+/// boolean maps to its corresponding byte based on position. A `true` value
+/// indicates the end of an equivalence class, where its corresponding byte
+/// and all of the bytes corresponding to all previous contiguous `false`
+/// values are in the same equivalence class.
+///
+/// This particular representation only permits contiguous ranges of bytes to
+/// be in the same equivalence class, which means that we can never discover
+/// the true minimal set of equivalence classes.
+#[cfg(feature = "std")]
+#[derive(Debug)]
+pub struct ByteClassSet(Vec<bool>);
+
+#[cfg(feature = "std")]
+impl ByteClassSet {
+    /// Create a new set of byte classes where all bytes are part of the same
+    /// equivalence class.
+    pub fn new() -> Self {
+        ByteClassSet(vec![false; 256])
+    }
+
+    /// Indicate the the range of byte given (inclusive) can discriminate a
+    /// match between it and all other bytes outside of the range.
+    pub fn set_range(&mut self, start: u8, end: u8) {
+        debug_assert!(start <= end);
+        if start > 0 {
+            self.0[start as usize - 1] = true;
+        }
+        self.0[end as usize] = true;
+    }
+
+    /// Convert this boolean set to a map that maps all byte values to their
+    /// corresponding equivalence class. The last mapping indicates the largest
+    /// equivalence class identifier (which is never bigger than 255).
+    pub fn byte_classes(&self) -> ByteClasses {
+        let mut classes = ByteClasses::empty();
+        let mut class = 0u8;
+        let mut i = 0;
+        loop {
+            classes.set(i as u8, class as u8);
+            if i >= 255 {
+                break;
+            }
+            if self.0[i] {
+                class = class.checked_add(1).unwrap();
+            }
+            i += 1;
+        }
+        classes
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[cfg(feature = "std")]
+    #[test]
+    fn byte_classes() {
+        use super::ByteClassSet;
+
+        let mut set = ByteClassSet::new();
+        set.set_range(b'a', b'z');
+
+        let classes = set.byte_classes();
+        assert_eq!(classes.get(0), 0);
+        assert_eq!(classes.get(1), 0);
+        assert_eq!(classes.get(2), 0);
+        assert_eq!(classes.get(b'a' - 1), 0);
+        assert_eq!(classes.get(b'a'), 1);
+        assert_eq!(classes.get(b'm'), 1);
+        assert_eq!(classes.get(b'z'), 1);
+        assert_eq!(classes.get(b'z' + 1), 2);
+        assert_eq!(classes.get(254), 2);
+        assert_eq!(classes.get(255), 2);
+
+        let mut set = ByteClassSet::new();
+        set.set_range(0, 2);
+        set.set_range(4, 6);
+        let classes = set.byte_classes();
+        assert_eq!(classes.get(0), 0);
+        assert_eq!(classes.get(1), 0);
+        assert_eq!(classes.get(2), 0);
+        assert_eq!(classes.get(3), 1);
+        assert_eq!(classes.get(4), 2);
+        assert_eq!(classes.get(5), 2);
+        assert_eq!(classes.get(6), 2);
+        assert_eq!(classes.get(7), 3);
+        assert_eq!(classes.get(255), 3);
+    }
+
+    #[cfg(feature = "std")]
+    #[test]
+    fn full_byte_classes() {
+        use super::ByteClassSet;
+
+        let mut set = ByteClassSet::new();
+        for i in 0..256u16 {
+            set.set_range(i as u8, i as u8);
+        }
+        assert_eq!(set.byte_classes().alphabet_len(), 256);
+    }
+}