1 files changed, 124 insertions, 0 deletions
diff --git a/components/util/vec.rs b/components/util/vec.rs
new file mode 100644
index 00000000000..b8d24687d28
--- /dev/null
+++ b/components/util/vec.rs
@@ -0,0 +1,124 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::cmp::{PartialOrd, PartialEq};
+
+/// FIXME(pcwalton): Workaround for lack of unboxed closures. This is called in
+/// performance-critical code, so a closure is insufficient.
+pub trait Comparator<K,T> {
+    fn compare(&self, key: &K, value: &T) -> Ordering;
+}
+
+pub trait BinarySearchMethods<'a, T: Ord + PartialOrd + PartialEq> {
+    fn binary_search(&self, key: &T) -> Option<&'a T>;
+    fn binary_search_index(&self, key: &T) -> Option<uint>;
+}
+
+pub trait FullBinarySearchMethods<T> {
+    fn binary_search_index_by<K,C:Comparator<K,T>>(&self, key: &K, cmp: C) -> Option<uint>;
+}
+
+impl<'a, T: Ord + PartialOrd + PartialEq> BinarySearchMethods<'a, T> for &'a [T] {
+    fn binary_search(&self, key: &T) -> Option<&'a T> {
+        self.binary_search_index(key).map(|i| &self[i])
+    }
+
+    fn binary_search_index(&self, key: &T) -> Option<uint> {
+        self.binary_search_index_by(key, DefaultComparator)
+    }
+}
+
+impl<'a, T> FullBinarySearchMethods<T> for &'a [T] {
+    fn binary_search_index_by<K,C:Comparator<K,T>>(&self, key: &K, cmp: C) -> Option<uint> {
+        if self.len() == 0 {
+            return None;
+        }
+
+        let mut low : int = 0;
+        let mut high : int = (self.len() as int) - 1;
+
+        while low <= high {
+            // http://googleresearch.blogspot.com/2006/06/extra-extra-read-all-about-it-nearly.html
+            let mid = ((low as uint) + (high as uint)) >> 1;
+            let midv = &self[mid];
+
+            match cmp.compare(key, midv) {
+                Greater => low = (mid as int) + 1,
+                Less => high = (mid as int) - 1,
+                Equal => return Some(mid),
+            }
+        }
+        return None;
+    }
+}
+
+struct DefaultComparator;
+
+impl<T:PartialEq + PartialOrd + Ord> Comparator<T,T> for DefaultComparator {
+    fn compare(&self, key: &T, value: &T) -> Ordering {
+        (*key).cmp(value)
+    }
+}
+
+#[cfg(test)]
+fn test_find_all_elems<T: PartialEq + PartialOrd + Eq + Ord>(arr: &[T]) {
+    let mut i = 0;
+    while i < arr.len() {
+        assert!(test_match(&arr[i], arr.binary_search(&arr[i])));
+        i += 1;
+    }
+}
+
+#[cfg(test)]
+fn test_miss_all_elems<T: PartialEq + PartialOrd + Eq + Ord>(arr: &[T], misses: &[T]) {
+    let mut i = 0;
+    while i < misses.len() {
+        let res = arr.binary_search(&misses[i]);
+        debug!("{:?} == {:?} ?", misses[i], res);
+        assert!(!test_match(&misses[i], arr.binary_search(&misses[i])));
+        i += 1;
+    }
+}
+
+#[cfg(test)]
+fn test_match<T: PartialEq>(b: &T, a: Option<&T>) -> bool {
+    match a {
+        None => false,
+        Some(t) => t == b
+    }
+}
+
+#[test]
+fn should_find_all_elements() {
+    let arr_odd = [1u32, 2, 4, 6, 7, 8, 9];
+    let arr_even = [1u32, 2, 5, 6, 7, 8, 9, 42];
+    let arr_double = [1u32, 1, 2, 2, 6, 8, 22];
+    let arr_one = [234986325u32];
+    let arr_two = [3044u32, 8393];
+    let arr_three = [12u32, 23, 34];
+
+    test_find_all_elems(arr_odd);
+    test_find_all_elems(arr_even);
+    test_find_all_elems(arr_double);
+    test_find_all_elems(arr_one);
+    test_find_all_elems(arr_two);
+    test_find_all_elems(arr_three);
+}
+
+#[test]
+fn should_not_find_missing_elements() {
+    let arr_odd = [1u32, 2, 4, 6, 7, 8, 9];
+    let arr_even = [1u32, 2, 5, 6, 7, 8, 9, 42];
+    let arr_double = [1u32, 1, 2, 2, 6, 8, 22];
+    let arr_one = [234986325u32];
+    let arr_two = [3044u32, 8393];
+    let arr_three = [12u32, 23, 34];
+
+    test_miss_all_elems(arr_odd, [-22, 0, 3, 5, 34938, 10, 11, 12]);
+    test_miss_all_elems(arr_even, [-1, 0, 3, 34938, 10, 11, 12]);
+    test_miss_all_elems(arr_double, [-1, 0, 3, 4, 34938, 10, 11, 12, 234, 234, 33]);
+    test_miss_all_elems(arr_one, [-1, 0, 3, 34938, 10, 11, 12, 234, 234, 33]);
+    test_miss_all_elems(arr_two, [-1, 0, 3, 34938, 10, 11, 12, 234, 234, 33]);
+    test_miss_all_elems(arr_three, [-2, 0, 1, 2, 3, 34938, 10, 11, 234, 234, 33]);
+}