refactor: ♻️ 2.0 (#3)

src/backend/NSExt/Extensions/CharExtensions.cs

@@ -0,0 +1,23 @@
+namespace NSExt.Extensions;
+
+/// <summary>
+///     CharExtensions
+/// </summary>
+public static class CharExtensions
+{
+    /// <summary>
+    ///     是否数字或大小写字母
+    /// </summary>
+    public static bool IsAsciiLetterOrDigit(this char me)
+    {
+        return (((uint)me - 'A') & ~0x20) < 26 || (uint)me - '0' < 10;
+    }
+
+    /// <summary>
+    ///     是否base64字符
+    /// </summary>
+    public static bool IsBase64Character(this char me)
+    {
+        return IsAsciiLetterOrDigit(me) || me is '+' or '/' or '=';
+    }
+}