Use u8 in a few more places (#70894)

* Use u8 in a few more places

* A few more u8s

src/libraries/System.Memory/src/System/Buffers/Text/Base64Encoder.cs

@@ -577,16 +577,6 @@ private static unsafe uint EncodeAndPadTwo(byte* oneByte, ref byte encodingMap)
 
         private const int MaximumEncodeLength = (int.MaxValue / 4) * 3; // 1610612733
 
-        // Pre-computing this table using a custom string(s_characters) and GenerateEncodingMapAndVerify (found in tests)
-        private static ReadOnlySpan<byte> EncodingMap => new byte[] {
-            65, 66, 67, 68, 69, 70, 71, 72,         //A..H
-            73, 74, 75, 76, 77, 78, 79, 80,         //I..P
-            81, 82, 83, 84, 85, 86, 87, 88,         //Q..X
-            89, 90, 97, 98, 99, 100, 101, 102,      //Y..Z, a..f
-            103, 104, 105, 106, 107, 108, 109, 110, //g..n
-            111, 112, 113, 114, 115, 116, 117, 118, //o..v
-            119, 120, 121, 122, 48, 49, 50, 51,     //w..z, 0..3
-            52, 53, 54, 55, 56, 57, 43, 47          //4..9, +, /
-        };
+        private static ReadOnlySpan<byte> EncodingMap => "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"u8;
     }
 }

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/ChunkedEncodingWriteStream.cs

@@ -11,7 +11,7 @@ internal sealed partial class HttpConnection : IDisposable
     {
         private sealed class ChunkedEncodingWriteStream : HttpContentWriteStream
         {
-            private static readonly byte[] s_finalChunkBytes = { (byte)'0', (byte)'\r', (byte)'\n', (byte)'\r', (byte)'\n' };
+            private static readonly byte[] s_finalChunkBytes = "0\r\n\r\n"u8.ToArray();
 
             public ChunkedEncodingWriteStream(HttpConnection connection) : base(connection)
             {

src/libraries/System.Net.HttpListener/src/System/Net/Windows/HttpListener.Windows.cs

@@ -35,11 +35,7 @@ public sealed unsafe partial class HttpListener
         // 0.5 seconds per request.  Respond with a 400 Bad Request.
         private const int UnknownHeaderLimit = 1000;
 
-        private static readonly byte[] s_wwwAuthenticateBytes = new byte[]
-        {
-            (byte) 'W', (byte) 'W', (byte) 'W', (byte) '-', (byte) 'A', (byte) 'u', (byte) 't', (byte) 'h',
-            (byte) 'e', (byte) 'n', (byte) 't', (byte) 'i', (byte) 'c', (byte) 'a', (byte) 't', (byte) 'e'
-        };
+        private static readonly byte[] s_wwwAuthenticateBytes = "WWW-Authenticate"u8.ToArray();
 
         private HttpListenerSession? _currentSession;
 

src/libraries/System.Net.Mail/src/System/Net/Mime/Base64Encoder.cs

@@ -7,14 +7,7 @@ namespace System.Net.Mime
 {
     internal sealed class Base64Encoder : ByteEncoder
     {
-        private static ReadOnlySpan<byte> Base64EncodeMap => new byte[]
-        {
-             65,  66,  67,  68,   69, 70,  71,  72,  73,  74,  75,  76,  77,  78,   79,  80,
-             81,  82,  83,  84,   85, 86,  87,  88,  89,  90,  97,  98,  99, 100,  101, 102,
-            103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115,  116, 117, 118,
-            119, 120, 121, 122,  48,  49,  50,  51,  52,  53,  54,  55,  56,  57,   43,  47,
-            61
-        };
+        private static ReadOnlySpan<byte> Base64EncodeMap => "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="u8;
 
         //the number of bytes needed to encode three bytes
         private const int SizeOfBase64EncodedBlock = 4;

src/libraries/System.Net.Primitives/src/System/Net/IPAddress.cs

@@ -24,11 +24,11 @@ public class IPAddress
 
         internal const uint LoopbackMaskHostOrder = 0xFF000000;
 
-        public static readonly IPAddress IPv6Any = new IPAddress((ReadOnlySpan<byte>) new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, 0);
-        public static readonly IPAddress IPv6Loopback = new IPAddress((ReadOnlySpan<byte>) new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 }, 0);
+        public static readonly IPAddress IPv6Any = new IPAddress((ReadOnlySpan<byte>)new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, 0);
+        public static readonly IPAddress IPv6Loopback = new IPAddress((ReadOnlySpan<byte>)new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 }, 0);
         public static readonly IPAddress IPv6None = IPv6Any;
 
-        private static readonly IPAddress s_loopbackMappedToIPv6 = new IPAddress((ReadOnlySpan<byte>) new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 255, 255, 127, 0, 0, 1 }, 0);
+        private static readonly IPAddress s_loopbackMappedToIPv6 = new IPAddress((ReadOnlySpan<byte>)new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 255, 255, 127, 0, 0, 1 }, 0);
 
         /// <summary>
         /// For IPv4 addresses, this field stores the Address.

src/libraries/System.Net.Security/src/System/Net/Security/TlsFrameHelper.cs

@@ -149,11 +149,11 @@ public override string ToString()
 
         public delegate bool HelloExtensionCallback(ref TlsFrameInfo info, ExtensionType type, ReadOnlySpan<byte> extensionsData);
 
-        private static byte[] s_protocolMismatch13 = new byte[] { (byte)TlsContentType.Alert, 3, 4, 0, 2, 2, 70 };
-        private static byte[] s_protocolMismatch12 = new byte[] { (byte)TlsContentType.Alert, 3, 3, 0, 2, 2, 70 };
-        private static byte[] s_protocolMismatch11 = new byte[] { (byte)TlsContentType.Alert, 3, 2, 0, 2, 2, 70 };
-        private static byte[] s_protocolMismatch10 = new byte[] { (byte)TlsContentType.Alert, 3, 1, 0, 2, 2, 70 };
-        private static byte[] s_protocolMismatch30 = new byte[] { (byte)TlsContentType.Alert, 3, 0, 0, 2, 2, 40 };
+        private static readonly byte[] s_protocolMismatch13 = new byte[] { (byte)TlsContentType.Alert, 3, 4, 0, 2, 2, 70 };
+        private static readonly byte[] s_protocolMismatch12 = new byte[] { (byte)TlsContentType.Alert, 3, 3, 0, 2, 2, 70 };
+        private static readonly byte[] s_protocolMismatch11 = new byte[] { (byte)TlsContentType.Alert, 3, 2, 0, 2, 2, 70 };
+        private static readonly byte[] s_protocolMismatch10 = new byte[] { (byte)TlsContentType.Alert, 3, 1, 0, 2, 2, 70 };
+        private static readonly byte[] s_protocolMismatch30 = new byte[] { (byte)TlsContentType.Alert, 3, 0, 0, 2, 2, 40 };
 
         private const int UInt24Size = 3;
         private const int RandomSize = 32;

src/libraries/System.Private.DataContractSerialization/src/System/Text/Base64Encoding.cs

@@ -23,14 +23,7 @@ internal sealed class Base64Encoding : Encoding
         };
 
         private const string Val2Char = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
-
-        private static ReadOnlySpan<byte> Val2byte => new byte[]
-        {
-            (byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', (byte)'F', (byte)'G', (byte)'H', (byte)'I', (byte)'J', (byte)'K', (byte)'L', (byte)'M', (byte)'N', (byte)'O', (byte)'P',
-            (byte)'Q', (byte)'R', (byte)'S', (byte)'T', (byte)'U', (byte)'V', (byte)'W', (byte)'X', (byte)'Y', (byte)'Z', (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f',
-            (byte)'g', (byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n', (byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u', (byte)'v',
-            (byte)'w', (byte)'x', (byte)'y', (byte)'z', (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6', (byte)'7', (byte)'8', (byte)'9', (byte)'+', (byte)'/'
-        };
+        private static ReadOnlySpan<byte> Val2byte => "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"u8;
 
         public override int GetMaxByteCount(int charCount)
         {

src/libraries/System.Private.DataContractSerialization/src/System/Xml/PrefixHandle.cs

@@ -23,7 +23,7 @@ internal sealed class PrefixHandle : IEquatable<PrefixHandle>
         private int _offset;
         private int _length;
         private static readonly string[] s_prefixStrings = { "", "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z" };
-        private static readonly byte[] s_prefixBuffer = { (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f', (byte)'g', (byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n', (byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u', (byte)'v', (byte)'w', (byte)'x', (byte)'y', (byte)'z' };
+        private static readonly byte[] s_prefixBuffer = "abcdefghijklmnopqrstuvwxyz"u8.ToArray();
 
         public PrefixHandle(XmlBufferReader bufferReader)
         {

src/libraries/System.Private.DataContractSerialization/src/System/Xml/XmlUTF8TextWriter.cs

@@ -51,28 +51,12 @@ internal class XmlUTF8NodeWriter : XmlStreamNodeWriter
         private Encoding? _encoding;
         private char[]? _chars;
 
-        private static readonly byte[] s_startDecl =
-        {
-            (byte)'<', (byte)'?', (byte)'x', (byte)'m', (byte)'l', (byte)' ',
-            (byte)'v', (byte)'e', (byte)'r', (byte)'s', (byte)'i', (byte)'o', (byte)'n', (byte)'=', (byte)'"', (byte)'1', (byte)'.', (byte)'0', (byte)'"', (byte)' ',
-            (byte)'e', (byte)'n', (byte)'c', (byte)'o', (byte)'d', (byte)'i', (byte)'n', (byte)'g', (byte)'=', (byte)'"',
-        };
-        private static readonly byte[] s_endDecl =
-        {
-            (byte)'"', (byte)'?', (byte)'>'
-        };
-        private static readonly byte[] s_utf8Decl =
-        {
-            (byte)'<', (byte)'?', (byte)'x', (byte)'m', (byte)'l', (byte)' ',
-            (byte)'v', (byte)'e', (byte)'r', (byte)'s', (byte)'i', (byte)'o', (byte)'n', (byte)'=', (byte)'"', (byte)'1', (byte)'.', (byte)'0', (byte)'"', (byte)' ',
-            (byte)'e', (byte)'n', (byte)'c', (byte)'o', (byte)'d', (byte)'i', (byte)'n', (byte)'g', (byte)'=', (byte)'"', (byte)'u', (byte)'t', (byte)'f', (byte)'-', (byte)'8', (byte)'"',
-            (byte)'?', (byte)'>'
-        };
-        private static ReadOnlySpan<byte> Digits => new byte[]
-        {
-            (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', (byte) '7',
-            (byte) '8', (byte) '9', (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F'
-        };
+        private static readonly byte[] s_startDecl = "<?xml version=\"1.0\" encoding=\""u8.ToArray();
+        private static readonly byte[] s_endDecl = "\"?>"u8.ToArray();
+        private static readonly byte[] s_utf8Decl = "<?xml version=\"1.0\" encoding=\"utf-8\"?>"u8.ToArray();
+
+        private static ReadOnlySpan<byte> Digits => "0123456789ABCDEF"u8;
+
         private static readonly bool[] s_defaultIsEscapedAttributeChar = new bool[]
         {
             true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true,