1 files changed, 90 insertions, 0 deletions
diff --git a/src/util/smallcharset.rs b/src/util/smallcharset.rs
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--- /dev/null
+++ b/src/util/smallcharset.rs
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+// Copyright 2014-2017 The html5ever Project Developers. See the
+// COPYRIGHT file at the top-level directory of this distribution.
+//
+// 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.
+
+//! This module contains a single struct [`SmallCharSet`]. See its documentation for details.
+//!
+//! [`SmallCharSet`]: struct.SmallCharSet.html
+
+/// Represents a set of "small characters", those with Unicode scalar
+/// values less than 64.
+///
+/// This is stored as a bitmap, with 1 bit for each value.
+#[derive(Debug, Eq, PartialEq, Clone, Copy, Hash)]
+pub struct SmallCharSet {
+    pub bits: u64,
+}
+
+impl SmallCharSet {
+    /// Checks whether a character (u8 value below 64) is stored in the SmallCharSet.
+    ///
+    /// # Examples
+    ///
+    /// ```ignore
+    /// # use markup5ever::SmallCharSet;
+    /// let set = SmallCharSet {
+    ///     bits: 0b00000000_01000000_00000100_00000000_00000000_00000000_00010000_00000000
+    /// };
+    /// assert!(set.contains(64));
+    /// assert!(set.contains(b'6')); // `b'6'` is the same as 64u8
+    /// ```
+    #[inline]
+    fn contains(&self, n: u8) -> bool {
+        0 != (self.bits & (1 << (n as usize)))
+    }
+
+    /// Count the number of bytes of characters at the beginning of `buf` which are not in the set.
+    ///
+    /// This functionality is used in [`BufferQueue::pop_except_from`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # #[macro_use] extern crate markup5ever;
+    /// # fn main() {
+    /// let set = small_char_set!(48 49 50); // '0' '1' '2'
+    /// // `test` is 4 chars, 😁 is 4 chars, then we meet a character in the set
+    /// let test_str = "test😁01232afd";
+    /// assert_eq!(set.nonmember_prefix_len(test_str), 8);
+    /// # }
+    /// ```
+    ///
+    /// [`BufferQueue::pop_except_from`]: buffer_queue/struct.BufferQueue.html#method.pop_except_from
+    pub fn nonmember_prefix_len(&self, buf: &str) -> u32 {
+        let mut n = 0;
+        for b in buf.bytes() {
+            if b >= 64 || !self.contains(b) {
+                n += 1;
+            } else {
+                break;
+            }
+        }
+        n
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use std::iter::repeat;
+
+    #[test]
+    fn nonmember_prefix() {
+        for &c in ['&', '\0'].iter() {
+            for x in 0..48u32 {
+                for y in 0..48u32 {
+                    let mut s = repeat("x").take(x as usize).collect::<String>();
+                    s.push(c);
+                    s.push_str(&repeat("x").take(y as usize).collect::<String>());
+                    let set = small_char_set!('&' '\0');
+
+                    assert_eq!(x, set.nonmember_prefix_len(&s));
+                }
+            }
+        }
+    }
+}