Optimize string.EndsWith(char) for const values (#69038)

Author: GrabYourPitchforks

src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs

@@ -2079,7 +2079,7 @@ private static void FilterHelper(
                     listType = MemberListType.CaseSensitive;
                 }
 
-                if (allowPrefixLookup && name.EndsWith("*", StringComparison.Ordinal))
+                if (allowPrefixLookup && name.EndsWith('*'))
                 {
                     // We set prefixLookup to true if name ends with a "*".
                     // We will also set listType to All so that all members are included in

src/libraries/Common/src/System/Net/CookieParser.cs

@@ -855,10 +855,9 @@ private static FieldInfo IsQuotedVersionField
 
         internal static string CheckQuoted(string value)
         {
-            if (value.Length < 2 || value[0] != '\"' || value[value.Length - 1] != '\"')
-                return value;
-
-            return value.Length == 2 ? string.Empty : value.Substring(1, value.Length - 2);
+            return (value.Length >= 2 && value.StartsWith('\"') && value.EndsWith('\"'))
+                ? value.Substring(1, value.Length - 2)
+                : value;
         }
 
         internal bool EndofHeader()

src/libraries/System.IO.Pipes/src/System/IO/Pipes/PipeStream.Unix.cs

@@ -202,7 +202,7 @@ internal static string GetPipePath(string serverName, string pipeName)
             // cross-platform with Windows (which has only '\' as an invalid char).
             if (Path.IsPathRooted(pipeName))
             {
-                if (pipeName.IndexOfAny(s_invalidPathNameChars) >= 0 || pipeName[pipeName.Length - 1] == Path.DirectorySeparatorChar)
+                if (pipeName.IndexOfAny(s_invalidPathNameChars) >= 0 || pipeName.EndsWith(Path.DirectorySeparatorChar))
                     throw new PlatformNotSupportedException(SR.PlatformNotSupported_InvalidPipeNameChars);
 
                 // Caller is in full control of file location.

src/libraries/System.Net.Http/src/System/Net/Http/Headers/CacheControlHeaderValue.cs

@@ -537,7 +537,7 @@ private static bool TrySetOptionalTokenList(NameValueHeaderValue nameValue, ref
             // We need the string to be at least 3 chars long: 2x quotes and at least 1 character. Also make sure we
             // have a quoted string. Note that NameValueHeaderValue will never have leading/trailing whitespace.
             string valueString = nameValue.Value;
-            if ((valueString.Length < 3) || (valueString[0] != '\"') || (valueString[valueString.Length - 1] != '\"'))
+            if ((valueString.Length < 3) || !valueString.StartsWith('\"') || !valueString.EndsWith('\"'))
             {
                 return false;
             }

src/libraries/System.Net.Http/src/System/Net/Http/Headers/NameValueHeaderValue.cs

@@ -358,7 +358,7 @@ private static void CheckValueFormat(string? value)
             }
 
             // Trailing/leading space are not allowed
-            if (value[0] == ' ' || value[0] == '\t' || value[^1] == ' ' || value[^1] == '\t')
+            if (value.StartsWith(' ') || value.StartsWith('\t') || value.EndsWith(' ') || value.EndsWith('\t'))
             {
                 ThrowFormatException(value);
             }

src/libraries/System.Net.Http/src/System/Net/Http/HttpContent.cs

@@ -192,8 +192,8 @@ internal static string ReadBufferAsString(ArraySegment<byte> buffer, HttpContent
                 {
                     // Remove at most a single set of quotes.
                     if (charset.Length > 2 &&
-                        charset[0] == '\"' &&
-                        charset[charset.Length - 1] == '\"')
+                        charset.StartsWith('\"') &&
+                        charset.EndsWith('\"'))
                     {
                         encoding = Encoding.GetEncoding(charset.Substring(1, charset.Length - 2));
                     }

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

@@ -146,7 +146,7 @@ internal void AddPrefix(string uriPrefix)
                 {
                     throw new ArgumentException(SR.net_listener_host, nameof(uriPrefix));
                 }
-                if (uriPrefix[uriPrefix.Length - 1] != '/')
+                if (!uriPrefix.EndsWith('/'))
                 {
                     throw new ArgumentException(SR.net_listener_slash, nameof(uriPrefix));
                 }

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

@@ -537,8 +537,8 @@ internal string GetString()
 
             internal static void FillFromString(NameValueCollection nvc, string s, bool urlencoded, Encoding encoding)
             {
+                int i = s.StartsWith('?') ? 1 : 0;
                 int l = s.Length;
-                int i = (l > 0 && s[0] == '?') ? 1 : 0;
 
                 while (i < l)
                 {

src/libraries/System.Net.HttpListener/src/System/Net/Managed/HttpEndPointListener.cs

@@ -178,7 +178,7 @@ public static void UnbindContext(HttpListenerContext context)
             string host = uri.Host;
             int port = uri.Port;
             string path = WebUtility.UrlDecode(uri.AbsolutePath);
-            string pathSlash = path[path.Length - 1] == '/' ? path : path + "/";
+            string pathSlash = path.EndsWith('/') ? path : path + "/";
 
             HttpListener? bestMatch = null;
             int bestLength = -1;

src/libraries/System.Net.Mail/src/System/Net/Mail/Attachment.cs

@@ -204,7 +204,7 @@ public string ContentId
                     ContentId = cid;
                     return cid;
                 }
-                if (cid.Length >= 2 && cid[0] == '<' && cid[cid.Length - 1] == '>')
+                if (cid.StartsWith('<') && cid.EndsWith('>'))
                 {
                     return cid.Substring(1, cid.Length - 2);
                 }