Bug 330101 nsTArray binary search for when array is sorted r=bsmedberg a=schrep

xpcom/glue/nsTArray.h

@@ -440,6 +440,36 @@ class nsTArray : public nsTArray_base {
       return LastIndexOf(item, start, nsDefaultComparator<elem_type, Item>());
     }
 
+    // This method searches for the offset for the element in this array
+    // that is equal to the given element. The array is assumed to be sorted.
+    // @param item   The item to search for.
+    // @param comp   The Comparator used.
+    // @return       The index of the found element or NoIndex if not found.
+    template<class Item, class Comparator>
+    index_type BinaryIndexOf(const Item& item, const Comparator& comp) const {
+      index_type low = 0, high = Length();
+      while (high > low) {
+        index_type mid = (high + low) >> 1;
+        if (comp.Equals(ElementAt(mid), item))
+          return mid;
+        if (comp.LessThan(ElementAt(mid), item))
+          low = mid + 1;
+        else
+          high = mid;
+      }
+      return NoIndex;
+    }
+
+    // This method searches for the offset for the element in this array
+    // that is equal to the given element. The array is assumed to be sorted.
+    // This method assumes that 'operator==' and 'operator<' are defined.
+    // @param item   The item to search for.
+    // @return       The index of the found element or NoIndex if not found.
+    template<class Item>
+    index_type BinaryIndexOf(const Item& item) const {
+      return BinaryIndexOf(item, nsDefaultComparator<elem_type, Item>());
+    }
+
     //
     // Mutation methods
     //

xpcom/tests/TestTArray.cpp

@@ -80,10 +80,18 @@ static PRBool test_basic_array(ElementType *data,
     return PR_FALSE;
   // ensure sort results in ascending order
   ary.Sort();
-  for (i = 1; i < ary.Length(); ++i) {
-    if (ary[i] < ary[i-1])
+  for (i = ary.Length(); --i; ) {
+    if (ary[i] < ary[i - 1])
+      return PR_FALSE;
+    if (ary[i] == ary[i - 1])
+      ary.RemoveElementAt(i);
+  }
+  for (i = 0; i < ary.Length(); ++i) {
+    if (ary.BinaryIndexOf(ary[i]) != i)
       return PR_FALSE;
   }
+  if (ary.BinaryIndexOf(extra) != -1)
+    return PR_FALSE;
   PRUint32 oldLen = ary.Length();
   ary.RemoveElement(data[dataLen / 2]);
   if (ary.Length() != (oldLen - 1))
@@ -285,10 +293,18 @@ static PRBool test_string_array() {
 
   strArray.Sort();
   const char ksorted[] = "\0 dehllloorw";
-  for (i = 0; i < NS_ARRAY_LENGTH(kdata)-1; ++i) {
+  for (i = NS_ARRAY_LENGTH(kdata); i--; ) {
     if (strArray[i].CharAt(0) != ksorted[i])
       return PR_FALSE;
+    if (i > 0 && strArray[i] == strArray[i - 1])
+      strArray.RemoveElementAt(i);
   }
+  for (i = 0; i < strArray.Length(); ++i) {
+    if (strArray.BinaryIndexOf(strArray[i]) != i)
+      return PR_FALSE;
+  }
+  if (strArray.BinaryIndexOf(EmptyCString()) != -1)
+    return PR_FALSE;
 
   nsCString rawArray[NS_ARRAY_LENGTH(kdata)-1];
   for (i = 0; i < NS_ARRAY_LENGTH(rawArray); ++i)