Array.Create<T> with default value

src/libraries/System.Formats.Tar/tests/TarFile/TarFile.ExtractToDirectory.Stream.Tests.cs

@@ -265,8 +265,7 @@ private async Task Extract_LinkEntry_TargetInsideDirectory_Internal(bool async,
         [MemberData(nameof(GetContentSizeAndBooleanData))]
         public async Task Extract_UnseekableStream_BlockAlignmentPadding_DoesNotAffectNextEntries(int contentSize, bool async)
         {
-            byte[] fileContents = new byte[contentSize];
-            Array.Fill<byte>(fileContents, 0x1);
+            byte[] fileContents = Array.CreateFilled<byte>(contentSize, 0x1);
 
             using MemoryStream archive = new MemoryStream();
             using (GZipStream compressor = new GZipStream(archive, CompressionMode.Compress, leaveOpen: true))
@@ -612,9 +611,8 @@ public void PaxExtraction_PathTraversalInEA_IsBlocked()
         [InlineData(100, 25)] // EA smaller than header
         public void PaxExtraction_EntryLengthMatchesExtractedFileSize(int dataSize, long eaSize)
         {
-            byte[] actualData = new byte[dataSize];
-            Array.Fill<byte>(actualData, (byte)'X');
-
+            byte[] actualData = Array.CreateFilled(dataSize, (byte)'X');
+
             byte[] archive = BuildRawPaxArchiveWithSizeOverride("file.bin", "file.bin", actualData, dataSize, eaSize);
 
             long apiLength;

src/libraries/System.Formats.Tar/tests/TarReader/TarReader.GetNextEntry.Tests.cs

@@ -44,8 +44,7 @@ public async Task MalformedArchive_TooSmall(bool async)
         public async Task MalformedArchive_HeaderSize(bool async)
         {
             using MemoryStream malformed = new MemoryStream();
-            byte[] buffer = new byte[512]; // Minimum length of any header
-            Array.Fill<byte>(buffer, 0x1);
+            byte[] buffer = Array.CreateFilled<byte>(512, 0x1); // Minimum length of any header
             malformed.Write(buffer);
             malformed.Seek(0, SeekOrigin.Begin);
 
@@ -92,8 +91,7 @@ public async Task LongEndMarkers_DoNotAdvanceStream(bool async)
                 await WriteEntry(writer, entry, async);
             }
 
-            byte[] buffer = new byte[2048]; // Four additional end markers (512 each)
-            Array.Fill<byte>(buffer, 0x0);
+            byte[] buffer = Array.CreateFilled<byte>(2048, 0x0); // Four additional end markers (512 each)
             archive.Write(buffer);
             archive.Seek(0, SeekOrigin.Begin);
 
@@ -337,8 +335,7 @@ public async Task GetNextEntry_UnseekableArchive_ReplaceDataStream_ExcludeFromDi
         [InlineData(1023, true, true)]
         public async Task BlockAlignmentPadding_DoesNotAffectNextEntries(int contentSize, bool copyData, bool async)
         {
-            byte[] fileContents = new byte[contentSize];
-            Array.Fill<byte>(fileContents, 0x1);
+            byte[] fileContents = Array.CreateFilled<byte>(contentSize, 0x1);
 
             using MemoryStream archive = new MemoryStream();
             {
@@ -544,9 +541,8 @@ public static IEnumerable<object[]> EASizeOverrideData()
         [MemberData(nameof(EASizeOverrideData))]
         public void PaxReader_EASizeOverridesHeaderSize(int actualDataSize, long headerSize, long eaSize)
         {
-            byte[] actualData = new byte[actualDataSize];
-            Array.Fill<byte>(actualData, (byte)'X');
-
+            byte[] actualData = Array.CreateFilled(actualDataSize, (byte)'X');
+
             byte[] archive = BuildRawPaxArchiveWithSizeOverride("file.bin", "file.bin", actualData, headerSize, eaSize);
 
             using var stream = new MemoryStream(archive);

src/libraries/System.IO.Compression/src/System/IO/Compression/DeflateManaged/HuffmanTree.cs

@@ -89,8 +89,7 @@ private static byte[] GetStaticLiteralTreeLength()
 
         private static byte[] GetStaticDistanceTreeLength()
         {
-            byte[] staticDistanceTreeLength = new byte[MaxDistTreeElements];
-            Array.Fill(staticDistanceTreeLength, (byte)5);
+            byte[] staticDistanceTreeLength = Array.CreateFilled<byte>(MaxDistTreeElements, 5);
             return staticDistanceTreeLength;
         }
 

src/libraries/System.IO.Compression/tests/ZipArchive/zip_InvalidParametersAndStrangeFiles.cs

@@ -327,9 +327,8 @@ public static async Task ZipArchiveEntry_CorruptedStream_EnsureNoExtraBytesReadO
             // the window portion [0, s_bufferSize), so the tail [s_bufferSize, end) must
             // never be touched regardless of how many iterations the loop takes.
             const int sentinelSize = 64;
-            byte[] buffer = new byte[s_bufferSize + sentinelSize];
-            Array.Fill<byte>(buffer, 0xDE);
-
+            byte[] buffer = Array.CreateFilled<byte>(s_bufferSize + sentinelSize, 0xDE);
+
             await Assert.ThrowsAsync<InvalidDataException>(async () =>
             {
                 int read;

src/libraries/System.Linq/tests/SumTests.cs

@@ -388,9 +388,8 @@ public void SumOfInt_SourceSumsToOverflow_OverflowExceptionThrown()
         [Fact]
         public void SumOfInt_SourceSumsToOverflowVectorHorizontally_OverflowExceptionThrown()
         {
-            int[] sourceInt = new int[Vector<int>.Count * 4];
-            Array.Fill(sourceInt, 0);
-
+            int[] sourceInt = Array.CreateFilled(Vector<int>.Count * 4, 0);
+
             for (int i = 0; i < Vector<int>.Count; i++)
             {
                 sourceInt[i] = int.MaxValue - 3;
@@ -407,8 +406,7 @@ public void SumOfInt_SourceSumsToOverflowVectorHorizontally_OverflowExceptionThr
         [MemberData(nameof(SumOverflowsVerticalVectorLanes))]
         public void SumOfInt_SourceSumsToOverflowVectorVertically_OverflowExceptionThrown(int element, int verticalOffset)
         {
-            int[] sourceInt = new int[Vector<int>.Count * 6];
-            Array.Fill(sourceInt, 0);
+            int[] sourceInt = Array.CreateFilled(Vector<int>.Count * 6, 0);
 
             sourceInt[element] = int.MaxValue;
             sourceInt[element + Vector<int>.Count * verticalOffset] = 1;
@@ -435,9 +433,8 @@ public void SumOfLong_SourceSumsToOverflow_OverflowExceptionThrown()
         [Fact]
         public void SumOfLong_SourceSumsToOverflowVectorHorizontally_OverflowExceptionThrown()
         {
-            long[] sourceLong = new long[Vector<long>.Count * 4];
-            Array.Fill(sourceLong, 0);
-
+            long[] sourceLong = Array.CreateFilled<long>(Vector<long>.Count * 4, 0);
+
             for (int i = 0; i < Vector<long>.Count; i++)
             {
                 sourceLong[i] = long.MaxValue - 3;
@@ -454,9 +451,8 @@ public void SumOfLong_SourceSumsToOverflowVectorHorizontally_OverflowExceptionTh
         [MemberData(nameof(SumOverflowsVerticalVectorLanes))]
         public void SumOfLong_SourceSumsToOverflowVectorVertically_OverflowExceptionThrown(int element, int verticalOffset)
         {
-            long[] sourceLong = new long[Vector<long>.Count * 6];
-            Array.Fill(sourceLong, 0);
-
+            long[] sourceLong = Array.CreateFilled<long>(Vector<long>.Count * 6, 0);
+
             sourceLong[element] = long.MaxValue;
             sourceLong[element + Vector<long>.Count * verticalOffset] = 1;
 

src/libraries/System.Memory/tests/MemoryMarshal/AsReadOnlyRef.cs

@@ -18,8 +18,7 @@ public static void AsReadOnlyRef()
             Assert.Equal(0x11222211, asInt);
             Assert.True(Unsafe.AreSame<byte>(ref Unsafe.As<int, byte>(ref Unsafe.AsRef(in asInt)), ref MemoryMarshal.GetReference(span)));
 
-            var array = new byte[100];
-            Array.Fill<byte>(array, 0x42);
+            byte[] array = Array.CreateFilled<byte>(100, 0x42);
             ref readonly TestHelpers.TestStructExplicit asStruct = ref MemoryMarshal.AsRef<TestHelpers.TestStructExplicit>(new ReadOnlySpan<byte>(array));
 
             Assert.Equal((uint)0x42424242, asStruct.UI1);

src/libraries/System.Memory/tests/MemoryMarshal/AsRef.cs

@@ -18,8 +18,7 @@ public static void AsRef()
             Assert.Equal(0x11222211, asInt);
             Assert.True(Unsafe.AreSame<byte>(ref Unsafe.As<int, byte>(ref asInt), ref MemoryMarshal.GetReference(span)));
 
-            var array = new byte[100];
-            Array.Fill<byte>(array, 0x42);
+            byte[] array = Array.CreateFilled<byte>(100, 0x42);
             ref TestHelpers.TestStructExplicit asStruct = ref MemoryMarshal.AsRef<TestHelpers.TestStructExplicit>(new Span<byte>(array));
 
             Assert.Equal((uint)0x42424242, asStruct.UI1);

src/libraries/System.Memory/tests/ReadOnlySpan/Count.byte.cs

@@ -166,8 +166,7 @@ public static void TestAlignmentNotCount_RosByte()
         [Fact]
         public static void TestAlignmentCount_Byte()
         {
-            byte[] array = new byte[4 * Vector<byte>.Count];
-            Array.Fill(array, (byte)5);
+            byte[] array = Array.CreateFilled<byte>(4 * Vector<byte>.Count, 5);
             for (var i = 0; i < Vector<byte>.Count; i++)
             {
                 var span = new ReadOnlySpan<byte>(array, i, 3 * Vector<byte>.Count);
@@ -181,8 +180,7 @@ public static void TestAlignmentCount_Byte()
         [Fact]
         public static void TestAlignmentCount_RosByte()
         {
-            byte[] array = new byte[4 * Vector<byte>.Count];
-            Array.Fill(array, (byte)5);
+            byte[] array = Array.CreateFilled<byte>(4 * Vector<byte>.Count, 5);
             for (var i = 0; i < Vector<byte>.Count; i++)
             {
                 var span = new ReadOnlySpan<byte>(array, i, 3 * Vector<byte>.Count);
@@ -260,10 +258,8 @@ public static void MakeSureNoCountChecksGoOutOfRange_RosByte()
         [Fact]
         public static void TestOverlapDoNotCount_RosByte()
         {
-            byte[] a = new byte[10];
-            Array.Fill<byte>(a, 6);
-
-
+            byte[] a = Array.CreateFilled<byte>(10, 6);
+
             var span = new ReadOnlySpan<byte>(a);
             Assert.Equal(5, span.Count(new byte[] { 6, 6 }));
         }

src/libraries/System.Memory/tests/ReadOnlySpan/IndexOfAny.T.cs

@@ -495,8 +495,7 @@ public static void DefaultFilledIndexOfAny_TwoString()
 
             for (int length = 0; length < byte.MaxValue; length++)
             {
-                var a = new string[length];
-                Array.Fill(a, "");
+                string[] a = Array.CreateFilled(length, "");
 
                 string[] targets = { "", "99" };
 
@@ -634,9 +633,8 @@ public static void DefaultFilledIndexOfAny_ThreeString()
 
             for (int length = 0; length < byte.MaxValue; length++)
             {
-                var a = new string[length];
-                Array.Fill(a, "");
-
+                string[] a = Array.CreateFilled(length, "");
+
                 string[] targets = { "", "99", "98" };
 
                 for (int i = 0; i < length; i++)
@@ -782,9 +780,8 @@ public static void DefaultFilledIndexOfAny_ManyString()
         {
             for (int length = 0; length < byte.MaxValue; length++)
             {
-                var a = new string[length];
-                Array.Fill(a, "");
-
+                string[] a = Array.CreateFilled(length, "");
+
                 var values = new string[] { "", "99", "98", "0" };
 
                 for (int i = 0; i < length; i++)

src/libraries/System.Memory/tests/ReadOnlySpan/LastIndexOfAny.T.cs

@@ -488,9 +488,8 @@ public static void DefaultFilledLastIndexOfAny_String_TwoByte()
 
             for (int length = 0; length < byte.MaxValue; length++)
             {
-                var a = new string[length];
-                Array.Fill(a, "");
-
+                string[] a = Array.CreateFilled(length, "");
+
                 string[] targets = { "", "99" };
 
                 for (int i = 0; i < length; i++)
@@ -624,8 +623,7 @@ public static void DefaultFilledLastIndexOfAny_String_ThreeByte()
 
             for (int length = 0; length < byte.MaxValue; length++)
             {
-                var a = new string[length];
-                Array.Fill(a, "");
+                string[] a = Array.CreateFilled(length, "");
 
                 string[] targets = { "", "99", "98" };
 
@@ -769,8 +767,7 @@ public static void DefaultFilledLastIndexOfAny_String_ManyByte()
         {
             for (int length = 0; length < byte.MaxValue; length++)
             {
-                var a = new string[length];
-                Array.Fill(a, "");
+                string[] a = Array.CreateFilled(length, "");
 
                 var values = new string[] { "", "99", "98", "0" };
 

src/libraries/System.Net.Security/tests/FunctionalTests/NegotiateAuthenticationKerberosTest.ChannelBindings.cs

@@ -103,8 +103,7 @@ private static SafeChannelBindingHandle CreateChannelBinding(ChannelBindingKind
         {
             const int HashLength = 32;
             SafeChannelBindingHandle handle = new SafeChannelBindingHandle(kind);
-            byte[] hash = new byte[HashLength];
-            Array.Fill(hash, hashSeed);
+            byte[] hash = Array.CreateFilled(HashLength, hashSeed);
             handle.SetCertHash(hash);
             return handle;
         }

src/libraries/System.Numerics.Tensors/tests/TensorPrimitives.Generic.cs

@@ -2708,11 +2708,8 @@ public void HammingBitDistance_KnownValues()
             T value42 = T.CreateTruncating(42);
             T value84 = T.CreateTruncating(84);
 
-            T[] values1 = new T[100];
-            T[] values2 = new T[100];
-
-            Array.Fill(values1, value42);
-            Array.Fill(values2, value84);
+            T[] values1 = Array.CreateFilled(100, value42);
+            T[] values2 = Array.CreateFilled(100, value84);
 
             Assert.Equal(0, TensorPrimitives.HammingBitDistance<T>(values1, values1));
             Assert.Equal(600, TensorPrimitives.HammingBitDistance<T>(values1, values2));
@@ -2885,10 +2882,9 @@ public void Clamp_UnorderedBoundsMatchScalarSemantics(int length)
             {
                 // Span x, span min, span max
                 {
-                    T[] min = new T[length];
-                    T[] max = new T[length];
-                    Array.Fill(min, zero);
-                    Array.Fill(max, two);
+                    T[] min = Array.CreateFilled(length, zero);
+                    T[] max = Array.CreateFilled(length, two);
+
                     min[offendingIndex] = two;
                     max[offendingIndex] = zero;
 
@@ -2902,8 +2898,7 @@ public void Clamp_UnorderedBoundsMatchScalarSemantics(int length)
 
                 // Span x, span min, scalar max
                 {
-                    T[] min = new T[length];
-                    Array.Fill(min, zero);
+                    T[] min = Array.CreateFilled(length, zero);
                     min[offendingIndex] = two;
 
                     TensorPrimitives.Clamp<T>(x, min, one, destination);
@@ -2916,8 +2911,7 @@ public void Clamp_UnorderedBoundsMatchScalarSemantics(int length)
 
                 // Span x, scalar min, span max
                 {
-                    T[] max = new T[length];
-                    Array.Fill(max, two);
+                    T[] max = Array.CreateFilled(length, two);
                     max[offendingIndex] = zero;
 
                     TensorPrimitives.Clamp<T>(x, one, max, destination);
@@ -2940,10 +2934,8 @@ public void Clamp_UnorderedBoundsMatchScalarSemantics(int length)
 
                 // Scalar x, span min, span max
                 {
-                    T[] min = new T[length];
-                    T[] max = new T[length];
-                    Array.Fill(min, zero);
-                    Array.Fill(max, two);
+                    T[] min = Array.CreateFilled(length, zero);
+                    T[] max = Array.CreateFilled(length, two);
                     min[offendingIndex] = two;
                     max[offendingIndex] = zero;
 
@@ -2957,8 +2949,7 @@ public void Clamp_UnorderedBoundsMatchScalarSemantics(int length)
 
                 // Scalar x, span min, scalar max
                 {
-                    T[] min = new T[length];
-                    Array.Fill(min, zero);
+                    T[] min = Array.CreateFilled(length, zero);
                     min[offendingIndex] = two;
 
                     TensorPrimitives.Clamp<T>(one, min, one, destination);
@@ -2971,8 +2962,7 @@ public void Clamp_UnorderedBoundsMatchScalarSemantics(int length)
 
                 // Scalar x, scalar min, span max
                 {
-                    T[] max = new T[length];
-                    Array.Fill(max, two);
+                    T[] max = Array.CreateFilled(length, two);
                     max[offendingIndex] = zero;
 
                     TensorPrimitives.Clamp<T>(one, one, max, destination);

src/libraries/System.Numerics.Tensors/tests/TensorTests.cs

@@ -1127,9 +1127,8 @@ public static void TensorIndexOfMinNonDenseTests(int[] data, nint[] shape, nint[
         {
             _ = expectedLogical;
             // Set all logical elements to positive values, then put the minimum at the last logical position
-            int[] testData = new int[data.Length];
-            Array.Fill(testData, 50);
-
+            int[] testData = Array.CreateFilled(data.Length, 50);
+
             nint flatLen = 1;
             foreach (nint s in shape)
             {
@@ -1173,9 +1172,8 @@ public static void TensorIndexOfMinNonDenseTests(int[] data, nint[] shape, nint[
         public static void TensorIndexOfMaxMagnitudeNonDenseTests(int[] data, nint[] shape, nint[] strides, int[] expectedLogical)
         {
             _ = expectedLogical;
-            int[] testData = new int[data.Length];
-            Array.Fill(testData, 1);
-
+            int[] testData = Array.CreateFilled(data.Length, 1);
+
             nint flatLen = 1;
             foreach (nint s in shape)
             {
@@ -1219,8 +1217,7 @@ public static void TensorIndexOfMaxMagnitudeNonDenseTests(int[] data, nint[] sha
         public static void TensorIndexOfMinMagnitudeNonDenseTests(int[] data, nint[] shape, nint[] strides, int[] expectedLogical)
         {
             _ = expectedLogical;
-            int[] testData = new int[data.Length];
-            Array.Fill(testData, 100);
+            int[] testData = Array.CreateFilled(data.Length, 100);
 
             nint flatLen = 1;
             foreach (nint s in shape)

src/libraries/System.Private.CoreLib/src/System/Array.cs

@@ -39,6 +39,23 @@ public static ReadOnlyCollection<T> AsReadOnly<T>(T[] array)
                 new ReadOnlyCollection<T>(array);
         }
 
+        /// <summary>
+        /// Creates a new array of the specified length, with each element initialized to the specified value.
+        /// </summary>
+        /// <param name="length">The length of the array.</param>
+        /// <param name="value">The value with which to initialize each element.</param>
+        /// <typeparam name="T">The type of the elements in the array.</typeparam>
+        /// <returns>A new array of the specified length, with each element initialized to <paramref name="value"/>.</returns>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="length"/> is negative.</exception>
+        public static T[] CreateFilled<T>(int length, T value)
+        {
+            ArgumentOutOfRangeException.ThrowIfNegative(length);
+
+            T[] array = GC.AllocateUninitializedArray<T>(length);
+            Fill(array, value);
+            return array;
+        }
+
         public static void Resize<T>([NotNull] ref T[]? array, int newSize)
         {
             if (newSize < 0)