diff -r 000000000000 -r 6474c204b198 mfbt/BinarySearch.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mfbt/BinarySearch.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,66 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef mozilla_BinarySearch_h
+#define mozilla_BinarySearch_h
+
+#include "mozilla/Assertions.h"
+
+#include <stddef.h>
+
+namespace mozilla {
+
+/*
+ * The algorithm searches the given container 'c' over the sorted index range
+ * [begin, end) for an index 'i' where 'c[i] == target'. If such an index 'i' is
+ * found, BinarySearch returns 'true' and the index is returned via the outparam
+ * 'matchOrInsertionPoint'. If no index is found, BinarySearch returns 'false'
+ * and the outparam returns the first index in [begin, end] where 'target' can
+ * be inserted to maintain sorted order.
+ *
+ * Example:
+ *
+ *   Vector<int> sortedInts = ...
+ *
+ *   size_t match;
+ *   if (BinarySearch(sortedInts, 0, sortedInts.length(), 13, &match))
+ *     printf("found 13 at %lu\n", match);
+ */
+
+template <typename Container, typename T>
+bool
+BinarySearch(const Container &c, size_t begin, size_t end, T target, size_t *matchOrInsertionPoint)
+{
+  MOZ_ASSERT(begin <= end);
+
+  size_t low = begin;
+  size_t high = end;
+  while (low != high) {
+    size_t middle = low + (high - low) / 2;
+    const T &middleValue = c[middle];
+
+    MOZ_ASSERT(c[low] <= c[middle]);
+    MOZ_ASSERT(c[middle] <= c[high - 1]);
+    MOZ_ASSERT(c[low] <= c[high - 1]);
+
+    if (target == middleValue) {
+      *matchOrInsertionPoint = middle;
+      return true;
+    }
+
+    if (target < middleValue)
+      high = middle;
+    else
+      low = middle + 1;
+  }
+
+  *matchOrInsertionPoint = low;
+  return false;
+}
+
+} // namespace mozilla
+
+#endif // mozilla_BinarySearch_h