Memory is safe again

csharp/Platform.Collections.Tests/CharsSegmentTests.cs

@@ -24,5 +24,17 @@ public static void EqualsTest()
             var second = new CharSegment(testArray, 5, 4);
             Assert.True(first.Equals(second));
         }
+
+        [Fact]
+        public static void Issue136()
+        {
+            const string str = "aaaaaaaaaa";
+            var test = str.ToCharArray();
+            var a = new CharSegment(test, 0, 3);
+            var b = new CharSegment(test, 7, 3);
+            Assert.True(a.Equals(b));
+            Assert.True(b.Equals(a));
+            Assert.Equal(a, b);
+        }
     }
 }

csharp/Platform.Collections/Arrays/CharArrayExtensions.cs

@@ -77,11 +77,11 @@ private static bool CheckArraysMainPartForEquality(ref char* left, ref char* rig
         {
             while (length >= 10)
             {
-                if ((*(int*)left != *(int*)right)
-                 || (*(int*)(left + 2) != *(int*)(right + 2))
-                 || (*(int*)(left + 4) != *(int*)(right + 4))
-                 || (*(int*)(left + 6) != *(int*)(right + 6))
-                 || (*(int*)(left + 8) != *(int*)(right + 8)))
+                if (*(int*)left != *(int*)right
+                 || *(int*)(left + 2) != *(int*)(right + 2)
+                 || *(int*)(left + 4) != *(int*)(right + 4)
+                 || *(int*)(left + 6) != *(int*)(right + 6)
+                 || *(int*)(left + 8) != *(int*)(right + 8))
                 {
                     return false;
                 }
@@ -94,11 +94,10 @@ private static bool CheckArraysMainPartForEquality(ref char* left, ref char* rig
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private static void CheckArraysRemainderForEquality(ref char* left, ref char* right, ref int length)
         {
-            // This depends on the fact that the String objects are
-            // always zero terminated and that the terminating zero is not included
-            // in the length. For odd string sizes, the last compare will include
-            // the zero terminator.
-            while (length > 0)
+            // It is not guaranteed that the array is zero terminated
+            // (string in csharp also is not zero terminated )
+            // This code mindlessly "touches" memory
+            while (length >= 2)
             {
                 if (*(int*)left != *(int*)right)
                 {
@@ -108,6 +107,12 @@ private static void CheckArraysRemainderForEquality(ref char* left, ref char* ri
                 right += 2;
                 length -= 2;
             }
+
+            // lenght is 1 or 0
+            if (length != 0 && *left == *right)
+            {
+                length = 0;
+            }
         }
     }
 }