ReadOnlySequence: Don't leak the flags that are on _startInteger and …

…_endInteger. (#47969) * ReadOnlySequence: Don't leak the flags that are on _startInteger and _endInteger. * Typo fix. * Added more tests + review fixes.
dotnet · Mar 17, 2021 · 29dbd32 · 29dbd32
1 parent 0f64b26
commit 29dbd32
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Showing 3 changed files with 37 additions and 3 deletions.
diff --git a/src/libraries/System.Memory/src/System/Buffers/ReadOnlySequence.Helpers.cs b/src/libraries/System.Memory/src/System/Buffers/ReadOnlySequence.Helpers.cs
@@ -248,7 +248,7 @@ internal SequencePosition Seek(long offset, ExceptionArgument exceptionArgument
                 int currentLength = startSegment.Memory.Length - startIndex;
 
                 // Position in start segment, defer to single segment seek
-                if (currentLength > offset)
+                if (currentLength > offset || offset == 0)
                     goto IsSingleSegment;
 
                 if (currentLength < 0)

diff --git a/src/libraries/System.Memory/src/System/Buffers/ReadOnlySequence.cs b/src/libraries/System.Memory/src/System/Buffers/ReadOnlySequence.cs
@@ -62,7 +62,7 @@ public bool IsSingleSegment
         public SequencePosition Start
         {
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            get => new SequencePosition(_startObject, _startInteger);
+            get => new SequencePosition(_startObject, GetIndex(_startInteger));
         }
 
         /// <summary>
@@ -71,7 +71,7 @@ public SequencePosition Start
         public SequencePosition End
         {
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            get => new SequencePosition(_endObject, _endInteger);
+            get => new SequencePosition(_endObject, GetIndex(_endInteger));
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -660,6 +660,10 @@ private enum SequenceType
 
     internal static class ReadOnlySequence
     {
+        /// <summary>
+        /// Flag that allows encoding the <see cref="ReadOnlySequence{T}.SequenceType"/>.
+        /// </summary>
+        /// <seealso cref="ReadOnlySequence{T}.GetSequenceType"/>
         public const int FlagBitMask = 1 << 31;
         public const int IndexBitMask = ~FlagBitMask;
 

diff --git a/src/libraries/System.Memory/tests/ReadOnlyBuffer/ReadOnlySequenceTests.byte.cs b/src/libraries/System.Memory/tests/ReadOnlyBuffer/ReadOnlySequenceTests.byte.cs
@@ -180,6 +180,36 @@ public void CopyTo_ThrowsWhenSourceLargerThenDestination()
             });
         }
 
+        [Fact]
+        public void End_EqualToGetPositionSize()
+        {
+            ReadOnlySequence<byte> buffer = Factory.CreateOfSize(5);
+            Assert.Equal(buffer.End, buffer.GetPosition(5));
+        }
+
+        [Fact]
+        public void Start_EqualToGetPosition0()
+        {
+            ReadOnlySequence<byte> buffer = Factory.CreateOfSize(5);
+            Assert.Equal(buffer.Start, buffer.GetPosition(0));
+        }
+
+        [Fact]
+        public void InnerPositionAreNotEqualToEnd()
+        {
+            ReadOnlySequence<byte> buffer = Factory.CreateOfSize(3);
+            Assert.NotEqual(buffer.GetPosition(1), buffer.End);
+            Assert.NotEqual(buffer.GetPosition(2), buffer.End);
+        }
+
+        [Fact]
+        public void InnerPositionAreNotEqualToStart()
+        {
+            ReadOnlySequence<byte> buffer = Factory.CreateOfSize(3);
+            Assert.NotEqual(buffer.GetPosition(1), buffer.Start);
+            Assert.NotEqual(buffer.GetPosition(2), buffer.Start);
+        }
+
         public static TheoryData<Func<ReadOnlySequence<byte>, ReadOnlySequence<byte>>> ValidSliceCases => new TheoryData<Func<ReadOnlySequence<byte>, ReadOnlySequence<byte>>>
         {
             b => b.Slice(5),