Import 'regex' package vesion 1.3.6

* Add OWNERS
* No Android.bp yet
Bug: 152884384
Test: make

Change-Id: I455caf7833b6c437c1c133bc7b2f47b83da9cbce
diff --git a/src/input.rs b/src/input.rs
new file mode 100644
index 0000000..3afa2d0
--- /dev/null
+++ b/src/input.rs
@@ -0,0 +1,434 @@
+use std::char;
+use std::cmp::Ordering;
+use std::fmt;
+use std::ops;
+use std::u32;
+
+use syntax;
+
+use literal::LiteralSearcher;
+use prog::InstEmptyLook;
+use utf8::{decode_last_utf8, decode_utf8};
+
+/// Represents a location in the input.
+#[derive(Clone, Copy, Debug)]
+pub struct InputAt {
+    pos: usize,
+    c: Char,
+    byte: Option<u8>,
+    len: usize,
+}
+
+impl InputAt {
+    /// Returns true iff this position is at the beginning of the input.
+    pub fn is_start(&self) -> bool {
+        self.pos == 0
+    }
+
+    /// Returns true iff this position is past the end of the input.
+    pub fn is_end(&self) -> bool {
+        self.c.is_none() && self.byte.is_none()
+    }
+
+    /// Returns the character at this position.
+    ///
+    /// If this position is just before or after the input, then an absent
+    /// character is returned.
+    pub fn char(&self) -> Char {
+        self.c
+    }
+
+    /// Returns the byte at this position.
+    pub fn byte(&self) -> Option<u8> {
+        self.byte
+    }
+
+    /// Returns the UTF-8 width of the character at this position.
+    pub fn len(&self) -> usize {
+        self.len
+    }
+
+    /// Returns whether the UTF-8 width of the character at this position
+    /// is zero.
+    pub fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+
+    /// Returns the byte offset of this position.
+    pub fn pos(&self) -> usize {
+        self.pos
+    }
+
+    /// Returns the byte offset of the next position in the input.
+    pub fn next_pos(&self) -> usize {
+        self.pos + self.len
+    }
+}
+
+/// An abstraction over input used in the matching engines.
+pub trait Input: fmt::Debug {
+    /// Return an encoding of the position at byte offset `i`.
+    fn at(&self, i: usize) -> InputAt;
+
+    /// Return the Unicode character occurring next to `at`.
+    ///
+    /// If no such character could be decoded, then `Char` is absent.
+    fn next_char(&self, at: InputAt) -> Char;
+
+    /// Return the Unicode character occurring previous to `at`.
+    ///
+    /// If no such character could be decoded, then `Char` is absent.
+    fn previous_char(&self, at: InputAt) -> Char;
+
+    /// Return true if the given empty width instruction matches at the
+    /// input position given.
+    fn is_empty_match(&self, at: InputAt, empty: &InstEmptyLook) -> bool;
+
+    /// Scan the input for a matching prefix.
+    fn prefix_at(
+        &self,
+        prefixes: &LiteralSearcher,
+        at: InputAt,
+    ) -> Option<InputAt>;
+
+    /// The number of bytes in the input.
+    fn len(&self) -> usize;
+
+    /// Whether the input is empty.
+    fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
+    /// Return the given input as a sequence of bytes.
+    fn as_bytes(&self) -> &[u8];
+}
+
+impl<'a, T: Input> Input for &'a T {
+    fn at(&self, i: usize) -> InputAt {
+        (**self).at(i)
+    }
+
+    fn next_char(&self, at: InputAt) -> Char {
+        (**self).next_char(at)
+    }
+
+    fn previous_char(&self, at: InputAt) -> Char {
+        (**self).previous_char(at)
+    }
+
+    fn is_empty_match(&self, at: InputAt, empty: &InstEmptyLook) -> bool {
+        (**self).is_empty_match(at, empty)
+    }
+
+    fn prefix_at(
+        &self,
+        prefixes: &LiteralSearcher,
+        at: InputAt,
+    ) -> Option<InputAt> {
+        (**self).prefix_at(prefixes, at)
+    }
+
+    fn len(&self) -> usize {
+        (**self).len()
+    }
+
+    fn as_bytes(&self) -> &[u8] {
+        (**self).as_bytes()
+    }
+}
+
+/// An input reader over characters.
+#[derive(Clone, Copy, Debug)]
+pub struct CharInput<'t>(&'t [u8]);
+
+impl<'t> CharInput<'t> {
+    /// Return a new character input reader for the given string.
+    pub fn new(s: &'t [u8]) -> CharInput<'t> {
+        CharInput(s)
+    }
+}
+
+impl<'t> ops::Deref for CharInput<'t> {
+    type Target = [u8];
+
+    fn deref(&self) -> &[u8] {
+        self.0
+    }
+}
+
+impl<'t> Input for CharInput<'t> {
+    fn at(&self, i: usize) -> InputAt {
+        if i >= self.len() {
+            InputAt { pos: self.len(), c: None.into(), byte: None, len: 0 }
+        } else {
+            let c = decode_utf8(&self[i..]).map(|(c, _)| c).into();
+            InputAt { pos: i, c: c, byte: None, len: c.len_utf8() }
+        }
+    }
+
+    fn next_char(&self, at: InputAt) -> Char {
+        at.char()
+    }
+
+    fn previous_char(&self, at: InputAt) -> Char {
+        decode_last_utf8(&self[..at.pos()]).map(|(c, _)| c).into()
+    }
+
+    fn is_empty_match(&self, at: InputAt, empty: &InstEmptyLook) -> bool {
+        use prog::EmptyLook::*;
+        match empty.look {
+            StartLine => {
+                let c = self.previous_char(at);
+                at.pos() == 0 || c == '\n'
+            }
+            EndLine => {
+                let c = self.next_char(at);
+                at.pos() == self.len() || c == '\n'
+            }
+            StartText => at.pos() == 0,
+            EndText => at.pos() == self.len(),
+            WordBoundary => {
+                let (c1, c2) = (self.previous_char(at), self.next_char(at));
+                c1.is_word_char() != c2.is_word_char()
+            }
+            NotWordBoundary => {
+                let (c1, c2) = (self.previous_char(at), self.next_char(at));
+                c1.is_word_char() == c2.is_word_char()
+            }
+            WordBoundaryAscii => {
+                let (c1, c2) = (self.previous_char(at), self.next_char(at));
+                c1.is_word_byte() != c2.is_word_byte()
+            }
+            NotWordBoundaryAscii => {
+                let (c1, c2) = (self.previous_char(at), self.next_char(at));
+                c1.is_word_byte() == c2.is_word_byte()
+            }
+        }
+    }
+
+    fn prefix_at(
+        &self,
+        prefixes: &LiteralSearcher,
+        at: InputAt,
+    ) -> Option<InputAt> {
+        prefixes.find(&self[at.pos()..]).map(|(s, _)| self.at(at.pos() + s))
+    }
+
+    fn len(&self) -> usize {
+        self.0.len()
+    }
+
+    fn as_bytes(&self) -> &[u8] {
+        self.0
+    }
+}
+
+/// An input reader over bytes.
+#[derive(Clone, Copy, Debug)]
+pub struct ByteInput<'t> {
+    text: &'t [u8],
+    only_utf8: bool,
+}
+
+impl<'t> ByteInput<'t> {
+    /// Return a new byte-based input reader for the given string.
+    pub fn new(text: &'t [u8], only_utf8: bool) -> ByteInput<'t> {
+        ByteInput { text: text, only_utf8: only_utf8 }
+    }
+}
+
+impl<'t> ops::Deref for ByteInput<'t> {
+    type Target = [u8];
+
+    fn deref(&self) -> &[u8] {
+        self.text
+    }
+}
+
+impl<'t> Input for ByteInput<'t> {
+    fn at(&self, i: usize) -> InputAt {
+        if i >= self.len() {
+            InputAt { pos: self.len(), c: None.into(), byte: None, len: 0 }
+        } else {
+            InputAt {
+                pos: i,
+                c: None.into(),
+                byte: self.get(i).cloned(),
+                len: 1,
+            }
+        }
+    }
+
+    fn next_char(&self, at: InputAt) -> Char {
+        decode_utf8(&self[at.pos()..]).map(|(c, _)| c).into()
+    }
+
+    fn previous_char(&self, at: InputAt) -> Char {
+        decode_last_utf8(&self[..at.pos()]).map(|(c, _)| c).into()
+    }
+
+    fn is_empty_match(&self, at: InputAt, empty: &InstEmptyLook) -> bool {
+        use prog::EmptyLook::*;
+        match empty.look {
+            StartLine => {
+                let c = self.previous_char(at);
+                at.pos() == 0 || c == '\n'
+            }
+            EndLine => {
+                let c = self.next_char(at);
+                at.pos() == self.len() || c == '\n'
+            }
+            StartText => at.pos() == 0,
+            EndText => at.pos() == self.len(),
+            WordBoundary => {
+                let (c1, c2) = (self.previous_char(at), self.next_char(at));
+                c1.is_word_char() != c2.is_word_char()
+            }
+            NotWordBoundary => {
+                let (c1, c2) = (self.previous_char(at), self.next_char(at));
+                c1.is_word_char() == c2.is_word_char()
+            }
+            WordBoundaryAscii => {
+                let (c1, c2) = (self.previous_char(at), self.next_char(at));
+                if self.only_utf8 {
+                    // If we must match UTF-8, then we can't match word
+                    // boundaries at invalid UTF-8.
+                    if c1.is_none() && !at.is_start() {
+                        return false;
+                    }
+                    if c2.is_none() && !at.is_end() {
+                        return false;
+                    }
+                }
+                c1.is_word_byte() != c2.is_word_byte()
+            }
+            NotWordBoundaryAscii => {
+                let (c1, c2) = (self.previous_char(at), self.next_char(at));
+                if self.only_utf8 {
+                    // If we must match UTF-8, then we can't match word
+                    // boundaries at invalid UTF-8.
+                    if c1.is_none() && !at.is_start() {
+                        return false;
+                    }
+                    if c2.is_none() && !at.is_end() {
+                        return false;
+                    }
+                }
+                c1.is_word_byte() == c2.is_word_byte()
+            }
+        }
+    }
+
+    fn prefix_at(
+        &self,
+        prefixes: &LiteralSearcher,
+        at: InputAt,
+    ) -> Option<InputAt> {
+        prefixes.find(&self[at.pos()..]).map(|(s, _)| self.at(at.pos() + s))
+    }
+
+    fn len(&self) -> usize {
+        self.text.len()
+    }
+
+    fn as_bytes(&self) -> &[u8] {
+        self.text
+    }
+}
+
+/// An inline representation of `Option<char>`.
+///
+/// This eliminates the need to do case analysis on `Option<char>` to determine
+/// ordinality with other characters.
+///
+/// (The `Option<char>` is not related to encoding. Instead, it is used in the
+/// matching engines to represent the beginning and ending boundaries of the
+/// search text.)
+#[derive(Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Char(u32);
+
+impl fmt::Debug for Char {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match char::from_u32(self.0) {
+            None => write!(f, "Empty"),
+            Some(c) => write!(f, "{:?}", c),
+        }
+    }
+}
+
+impl Char {
+    /// Returns true iff the character is absent.
+    #[inline]
+    pub fn is_none(self) -> bool {
+        self.0 == u32::MAX
+    }
+
+    /// Returns the length of the character's UTF-8 encoding.
+    ///
+    /// If the character is absent, then `1` is returned.
+    #[inline]
+    pub fn len_utf8(self) -> usize {
+        char::from_u32(self.0).map_or(1, |c| c.len_utf8())
+    }
+
+    /// Returns true iff the character is a word character.
+    ///
+    /// If the character is absent, then false is returned.
+    pub fn is_word_char(self) -> bool {
+        // is_word_character can panic if the Unicode data for \w isn't
+        // available. However, our compiler ensures that if a Unicode word
+        // boundary is used, then the data must also be available. If it isn't,
+        // then the compiler returns an error.
+        char::from_u32(self.0).map_or(false, syntax::is_word_character)
+    }
+
+    /// Returns true iff the byte is a word byte.
+    ///
+    /// If the byte is absent, then false is returned.
+    pub fn is_word_byte(self) -> bool {
+        match char::from_u32(self.0) {
+            Some(c) if c <= '\u{7F}' => syntax::is_word_byte(c as u8),
+            None | Some(_) => false,
+        }
+    }
+}
+
+impl From<char> for Char {
+    fn from(c: char) -> Char {
+        Char(c as u32)
+    }
+}
+
+impl From<Option<char>> for Char {
+    fn from(c: Option<char>) -> Char {
+        c.map_or(Char(u32::MAX), |c| c.into())
+    }
+}
+
+impl PartialEq<char> for Char {
+    #[inline]
+    fn eq(&self, other: &char) -> bool {
+        self.0 == *other as u32
+    }
+}
+
+impl PartialEq<Char> for char {
+    #[inline]
+    fn eq(&self, other: &Char) -> bool {
+        *self as u32 == other.0
+    }
+}
+
+impl PartialOrd<char> for Char {
+    #[inline]
+    fn partial_cmp(&self, other: &char) -> Option<Ordering> {
+        self.0.partial_cmp(&(*other as u32))
+    }
+}
+
+impl PartialOrd<Char> for char {
+    #[inline]
+    fn partial_cmp(&self, other: &Char) -> Option<Ordering> {
+        (*self as u32).partial_cmp(&other.0)
+    }
+}