Implement Span LastIndexOf extension method and add tests

src/Common/src/System/NotImplemented.cs

@@ -26,6 +26,6 @@ internal static Exception ByDesignWithMessage(string message)
         /// Temporary NotImplementedException with no message shown to user.
         /// Example: Exception.ActiveIssue("https://github.com/dotnet/corefx/issues/xxxx") or Exception.ActiveIssue("TFS xxxxxx").
         /// </summary>
-        internal static Exception ActiveIssue(string issue) => new NotImplementedException(); 
+        internal static Exception ActiveIssue(string issue) => new NotImplementedException();
     }
 }

src/Common/tests/System/PerfUtils.cs

@@ -41,7 +41,7 @@ public string CreateString(int length)
             for (int i = 0; i < str.Length; i++)
             {
                 // Add path separator so folders aren't too long.
-                if (i%20 == 0)
+                if (i % 20 == 0)
                 {
                     str[i] = Path.DirectorySeparatorChar;
                 }

src/System.Memory/ref/System.Memory.cs

@@ -15,7 +15,7 @@ public readonly ref struct ReadOnlySpan<T>
         [CLSCompliant(false)]
         public unsafe ReadOnlySpan(void* pointer, int length) { throw null; }
         public bool IsEmpty { get { throw null; } }
-        public T this[int index] { get { throw null; }}
+        public T this[int index] { get { throw null; } }
         public int Length { get { throw null; } }
         public void CopyTo(Span<T> destination) { }
         [System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
@@ -32,8 +32,8 @@ public void CopyTo(Span<T> destination) { }
         public override int GetHashCode() { throw null; }
 #pragma warning restore 0809
         public static bool operator ==(ReadOnlySpan<T> left, ReadOnlySpan<T> right) { throw null; }
-        public static implicit operator ReadOnlySpan<T> (T[] array) { throw null; }
-        public static implicit operator ReadOnlySpan<T> (ArraySegment<T> arraySegment) { throw null; }
+        public static implicit operator ReadOnlySpan<T>(T[] array) { throw null; }
+        public static implicit operator ReadOnlySpan<T>(ArraySegment<T> arraySegment) { throw null; }
         public static bool operator !=(ReadOnlySpan<T> left, ReadOnlySpan<T> right) { throw null; }
         public ReadOnlySpan<T> Slice(int start) { throw null; }
         public ReadOnlySpan<T> Slice(int start, int length) { throw null; }
@@ -73,9 +73,9 @@ public void CopyTo(Span<T> destination) { }
         public override int GetHashCode() { throw null; }
 #pragma warning restore 0809
         public static bool operator ==(Span<T> left, Span<T> right) { throw null; }
-        public static implicit operator Span<T> (T[] array) { throw null; }
-        public static implicit operator Span<T> (ArraySegment<T> arraySegment) { throw null; }
-        public static implicit operator ReadOnlySpan<T> (Span<T> span) { throw null; }
+        public static implicit operator Span<T>(T[] array) { throw null; }
+        public static implicit operator Span<T>(ArraySegment<T> arraySegment) { throw null; }
+        public static implicit operator ReadOnlySpan<T>(Span<T> span) { throw null; }
         public static bool operator !=(Span<T> left, Span<T> right) { throw null; }
         public Span<T> Slice(int start) { throw null; }
         public Span<T> Slice(int start, int length) { throw null; }
@@ -87,7 +87,7 @@ public ref struct Enumerator
             public ref T Current { get { throw null; } }
         }
     }
-    
+
     public static class MemoryExtensions
     {
         public static int IndexOf<T>(this Span<T> span, T value) where T : IEquatable<T> { throw null; }
@@ -97,8 +97,11 @@ public static class MemoryExtensions
         public static int IndexOfAny(this Span<byte> span, byte value0, byte value1, byte value2) { throw null; }
         public static int IndexOfAny(this Span<byte> span, ReadOnlySpan<byte> values) { throw null; }
 
+        public static int LastIndexOf<T>(this Span<T> span, T value) where T : IEquatable<T> { throw null; }
+        public static int LastIndexOf<T>(this Span<T> span, ReadOnlySpan<T> value) where T : IEquatable<T> { throw null; }
+
         public static bool SequenceEqual<T>(this Span<T> first, ReadOnlySpan<T> second) where T : IEquatable<T> { throw null; }
-        
+
         public static bool StartsWith<T>(this Span<T> span, ReadOnlySpan<T> value) where T : IEquatable<T> { throw null; }
 
         public static bool EndsWith<T>(this Span<T> span, ReadOnlySpan<T> value) where T : IEquatable<T> { throw null; }
@@ -107,7 +110,7 @@ public static class MemoryExtensions
         public static Span<byte> AsBytes<T>(this Span<T> source) where T : struct { throw null; }
 
         public static Span<TTo> NonPortableCast<TFrom, TTo>(this Span<TFrom> source) where TFrom : struct where TTo : struct { throw null; }
-        
+
         public static ReadOnlySpan<char> AsReadOnlySpan(this string text) { throw null; }
         public static ReadOnlyMemory<char> AsReadOnlyMemory(this string text) { throw null; }
 
@@ -128,12 +131,15 @@ public static class MemoryExtensions
         public static int IndexOfAny(this ReadOnlySpan<byte> span, byte value0, byte value1, byte value2) { throw null; }
         public static int IndexOfAny(this ReadOnlySpan<byte> span, ReadOnlySpan<byte> values) { throw null; }
 
+        public static int LastIndexOf<T>(this ReadOnlySpan<T> span, T value) where T : IEquatable<T> { throw null; }
+        public static int LastIndexOf<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> value) where T : IEquatable<T> { throw null; }
+
         public static bool SequenceEqual<T>(this ReadOnlySpan<T> first, ReadOnlySpan<T> second) where T : IEquatable<T> { throw null; }
 
         public static bool StartsWith<T>(this ReadOnlySpan<T> span, ReadOnlySpan<T> value) where T : IEquatable<T> { throw null; }
 
         public static ReadOnlySpan<byte> AsBytes<T>(this ReadOnlySpan<T> source) where T : struct { throw null; }
-        
+
         public static ReadOnlySpan<TTo> NonPortableCast<TFrom, TTo>(this ReadOnlySpan<TFrom> source) where TFrom : struct where TTo : struct { throw null; }
 
         public static bool TryGetString(this ReadOnlyMemory<char> readOnlyMemory, out string text, out int start, out int length) { throw null; }
@@ -197,23 +203,23 @@ public void CopyTo(Memory<T> destination) { }
 
 namespace System.Buffers
 {
-    public unsafe struct MemoryHandle : IDisposable 
+    public unsafe struct MemoryHandle : IDisposable
     {
         [CLSCompliant(false)]
-        public MemoryHandle(IRetainable owner, void* pointer = null,  System.Runtime.InteropServices.GCHandle handle = default(System.Runtime.InteropServices.GCHandle))  { throw null; }
+        public MemoryHandle(IRetainable owner, void* pointer = null, System.Runtime.InteropServices.GCHandle handle = default) { throw null; }
         [CLSCompliant(false)]
         public void* Pointer { get { throw null; } }
         public bool HasPointer { get { throw null; } }
         public void Dispose() { throw null; }
     }
 
-    public interface IRetainable 
+    public interface IRetainable
     {
         bool Release();
         void Retain();
     }
-    
-    public abstract class OwnedMemory<T> : IDisposable, IRetainable 
+
+    public abstract class OwnedMemory<T> : IDisposable, IRetainable
     {
         public Memory<T> Memory { get { throw null; } }
         public abstract bool IsDisposed { get; }
@@ -353,7 +359,7 @@ namespace System.Buffers
         public bool IsDefault => throw null;
         public byte Precision => throw null;
         public char Symbol => throw null;
-        public static implicit operator StandardFormat (char symbol) => throw null;
+        public static implicit operator StandardFormat(char symbol) => throw null;
         public static StandardFormat Parse(ReadOnlySpan<char> format) => throw null;
         public static StandardFormat Parse(string format) => throw null;
         public override bool Equals(object obj) => throw null;

src/System.Memory/src/System/Buffers/Binary/ReaderLittleEndian.cs

@@ -94,7 +94,7 @@ public static ulong ReadUInt64LittleEndian(ReadOnlySpan<byte> buffer)
             }
             return result;
         }
-        
+
         /// <summary>
         /// Reads an Int16 out of a read-only span of bytes as little endian.
         /// <returns>If the span is too small to contain an Int16, return false.</returns>

src/System.Memory/src/System/Buffers/MemoryHandle.cs

@@ -63,20 +63,20 @@ internal void AddOffset(int offset)
         /// Frees the pinned handle and releases IRetainable.
         /// </summary>
         public void Dispose()
-        { 
-            if (_handle.IsAllocated) 
+        {
+            if (_handle.IsAllocated)
             {
                 _handle.Free();
             }
 
-            if (_retainable != null) 
+            if (_retainable != null)
             {
                 _retainable.Release();
                 _retainable = null;
             }
 
-            _pointer = null;           
+            _pointer = null;
         }
-        
+
     }
 }

src/System.Memory/src/System/Buffers/OwnedMemory.cs

@@ -32,9 +32,9 @@ public abstract class OwnedMemory<T> : IDisposable, IRetainable
         /// </exception>
         public Memory<T> Memory
         {
-            get 
+            get
             {
-                if (IsDisposed) 
+                if (IsDisposed)
                 {
                     ThrowHelper.ThrowObjectDisposedException_MemoryDisposed(nameof(OwnedMemory<T>));
                 }
@@ -60,7 +60,7 @@ public Memory<T> Memory
         /// </exception>
         public void Dispose()
         {
-            if (IsRetained) 
+            if (IsRetained)
             {
                 ThrowHelper.ThrowInvalidOperationException_OutstandingReferences();
             }

src/System.Memory/src/System/Buffers/Text/Base64Decoder.cs

@@ -36,7 +36,8 @@ public static OperationStatus DecodeFromUtf8(ReadOnlySpan<byte> utf8, Span<byte>
             int sourceIndex = 0;
             int destIndex = 0;
 
-            if (utf8.Length == 0) goto DoneExit;
+            if (utf8.Length == 0)
+                goto DoneExit;
 
             ref sbyte decodingMap = ref s_decodingMap[0];
 
@@ -59,24 +60,27 @@ public static OperationStatus DecodeFromUtf8(ReadOnlySpan<byte> utf8, Span<byte>
             while (sourceIndex < maxSrcLength)
             {
                 int result = Decode(ref Unsafe.Add(ref srcBytes, sourceIndex), ref decodingMap);
-                if (result < 0) goto InvalidExit;
+                if (result < 0)
+                    goto InvalidExit;
                 WriteThreeLowOrderBytes(ref Unsafe.Add(ref destBytes, destIndex), result);
                 destIndex += 3;
                 sourceIndex += 4;
             }
 
-            if (maxSrcLength != srcLength - skipLastChunk) goto DestinationSmallExit;
+            if (maxSrcLength != srcLength - skipLastChunk)
+                goto DestinationSmallExit;
 
             // If input is less than 4 bytes, srcLength == sourceIndex == 0
             // If input is not a multiple of 4, sourceIndex == srcLength != 0
             if (sourceIndex == srcLength)
             {
-                if (isFinalBlock) goto InvalidExit;
+                if (isFinalBlock)
+                    goto InvalidExit;
                 goto NeedMoreExit;
             }
 
             // if isFinalBlock is false, we will never reach this point
-            
+
             int i0 = Unsafe.Add(ref srcBytes, srcLength - 4);
             int i1 = Unsafe.Add(ref srcBytes, srcLength - 3);
             int i2 = Unsafe.Add(ref srcBytes, srcLength - 2);
@@ -100,8 +104,10 @@ public static OperationStatus DecodeFromUtf8(ReadOnlySpan<byte> utf8, Span<byte>
                 i0 |= i3;
                 i0 |= i2;
 
-                if (i0 < 0) goto InvalidExit;
-                if (destIndex > destLength - 3) goto DestinationSmallExit;
+                if (i0 < 0)
+                    goto InvalidExit;
+                if (destIndex > destLength - 3)
+                    goto DestinationSmallExit;
                 WriteThreeLowOrderBytes(ref Unsafe.Add(ref destBytes, destIndex), i0);
                 destIndex += 3;
             }
@@ -113,41 +119,47 @@ public static OperationStatus DecodeFromUtf8(ReadOnlySpan<byte> utf8, Span<byte>
 
                 i0 |= i2;
 
-                if (i0 < 0) goto InvalidExit;
-                if (destIndex > destLength - 2) goto DestinationSmallExit;
+                if (i0 < 0)
+                    goto InvalidExit;
+                if (destIndex > destLength - 2)
+                    goto DestinationSmallExit;
                 Unsafe.Add(ref destBytes, destIndex) = (byte)(i0 >> 16);
                 Unsafe.Add(ref destBytes, destIndex + 1) = (byte)(i0 >> 8);
                 destIndex += 2;
             }
             else
             {
-                if (i0 < 0) goto InvalidExit;
-                if (destIndex > destLength - 1) goto DestinationSmallExit;
+                if (i0 < 0)
+                    goto InvalidExit;
+                if (destIndex > destLength - 1)
+                    goto DestinationSmallExit;
                 Unsafe.Add(ref destBytes, destIndex) = (byte)(i0 >> 16);
                 destIndex += 1;
             }
 
             sourceIndex += 4;
 
-            if (srcLength != utf8.Length) goto InvalidExit;
+            if (srcLength != utf8.Length)
+                goto InvalidExit;
 
-            DoneExit:
+        DoneExit:
             consumed = sourceIndex;
             written = destIndex;
             return OperationStatus.Done;
 
-            DestinationSmallExit:
-            if (srcLength != utf8.Length && isFinalBlock) goto InvalidExit; // if input is not a multiple of 4, and there is no more data, return invalid data instead
+        DestinationSmallExit:
+            if (srcLength != utf8.Length && isFinalBlock)
+                goto InvalidExit; // if input is not a multiple of 4, and there is no more data, return invalid data instead
             consumed = sourceIndex;
             written = destIndex;
             return OperationStatus.DestinationTooSmall;
 
-            NeedMoreExit:
+        NeedMoreExit:
             consumed = sourceIndex;
             written = destIndex;
             return OperationStatus.NeedMoreData;
 
-            InvalidExit:
+        InvalidExit:
             consumed = sourceIndex;
             written = destIndex;
             return OperationStatus.InvalidData;
@@ -190,8 +202,10 @@ public static OperationStatus DecodeFromUtf8InPlace(Span<byte> buffer, out int w
             int destIndex = 0;
 
             // only decode input if it is a multiple of 4
-            if (bufferLength != ((bufferLength >> 2) * 4)) goto InvalidExit;
-            if (bufferLength == 0) goto DoneExit;
+            if (bufferLength != ((bufferLength >> 2) * 4))
+                goto InvalidExit;
+            if (bufferLength == 0)
+                goto DoneExit;
 
             ref byte bufferBytes = ref buffer.DangerousGetPinnableReference();
 
@@ -200,7 +214,8 @@ public static OperationStatus DecodeFromUtf8InPlace(Span<byte> buffer, out int w
             while (sourceIndex < bufferLength - 4)
             {
                 int result = Decode(ref Unsafe.Add(ref bufferBytes, sourceIndex), ref decodingMap);
-                if (result < 0) goto InvalidExit;
+                if (result < 0)
+                    goto InvalidExit;
                 WriteThreeLowOrderBytes(ref Unsafe.Add(ref bufferBytes, destIndex), result);
                 destIndex += 3;
                 sourceIndex += 4;
@@ -229,7 +244,8 @@ public static OperationStatus DecodeFromUtf8InPlace(Span<byte> buffer, out int w
                 i0 |= i3;
                 i0 |= i2;
 
-                if (i0 < 0) goto InvalidExit;
+                if (i0 < 0)
+                    goto InvalidExit;
                 WriteThreeLowOrderBytes(ref Unsafe.Add(ref bufferBytes, destIndex), i0);
                 destIndex += 3;
             }
@@ -241,23 +257,25 @@ public static OperationStatus DecodeFromUtf8InPlace(Span<byte> buffer, out int w
 
                 i0 |= i2;
 
-                if (i0 < 0) goto InvalidExit;
+                if (i0 < 0)
+                    goto InvalidExit;
                 Unsafe.Add(ref bufferBytes, destIndex) = (byte)(i0 >> 16);
                 Unsafe.Add(ref bufferBytes, destIndex + 1) = (byte)(i0 >> 8);
                 destIndex += 2;
             }
             else
             {
-                if (i0 < 0) goto InvalidExit;
+                if (i0 < 0)
+                    goto InvalidExit;
                 Unsafe.Add(ref bufferBytes, destIndex) = (byte)(i0 >> 16);
                 destIndex += 1;
             }
 
-            DoneExit:
+        DoneExit:
             written = destIndex;
             return OperationStatus.Done;
 
-            InvalidExit:
+        InvalidExit:
             written = destIndex;
             return OperationStatus.InvalidData;
         }