Base for 4.3 work. Split Nadeko.Common into a separate project

src/Nadeko.Common/Kwum.cs

@@ -0,0 +1,100 @@
+using System.Runtime.CompilerServices;
+
+namespace Nadeko.Common;
+
+// needs proper invalid input check (character array input out of range)
+// needs negative number support
+// ReSharper disable once InconsistentNaming
+#pragma warning disable IDE1006
+public readonly struct kwum : IEquatable<kwum>
+#pragma warning restore IDE1006
+{
+    private const string VALID_CHARACTERS = "23456789abcdefghijkmnpqrstuvwxyz";
+    private readonly int _value;
+
+    public kwum(int num)
+        => _value = num;
+
+    public kwum(in char c)
+    {
+        if (!IsValidChar(c))
+            throw new ArgumentException("Character needs to be a valid kwum character.", nameof(c));
+
+        _value = InternalCharToValue(c);
+    }
+
+    public kwum(in ReadOnlySpan<char> input)
+    {
+        _value = 0;
+        for (var index = 0; index < input.Length; index++)
+        {
+            var c = input[index];
+            if (!IsValidChar(c))
+                throw new ArgumentException("All characters need to be a valid kwum characters.", nameof(input));
+
+            _value += VALID_CHARACTERS.IndexOf(c) * (int)Math.Pow(VALID_CHARACTERS.Length, input.Length - index - 1);
+        }
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static int InternalCharToValue(in char c)
+        => VALID_CHARACTERS.IndexOf(c);
+
+    public static bool TryParse(in ReadOnlySpan<char> input, out kwum value)
+    {
+        value = default;
+        foreach (var c in input)
+        {
+            if (!IsValidChar(c))
+                return false;
+        }
+
+        value = new(input);
+        return true;
+    }
+
+    public static kwum operator +(kwum left, kwum right)
+        => new(left._value + right._value);
+
+    public static bool operator ==(kwum left, kwum right)
+        => left._value == right._value;
+
+    public static bool operator !=(kwum left, kwum right)
+        => !(left == right);
+
+    public static implicit operator long(kwum kwum)
+        => kwum._value;
+
+    public static implicit operator int(kwum kwum)
+        => kwum._value;
+
+    public static implicit operator kwum(int num)
+        => new(num);
+
+    public static bool IsValidChar(char c)
+        => VALID_CHARACTERS.Contains(c);
+
+    public override string ToString()
+    {
+        var count = VALID_CHARACTERS.Length;
+        var localValue = _value;
+        var arrSize = (int)Math.Log(localValue, count) + 1;
+        Span<char> chars = new char[arrSize];
+        while (localValue > 0)
+        {
+            localValue = Math.DivRem(localValue, count, out var rem);
+            chars[--arrSize] = VALID_CHARACTERS[rem];
+        }
+
+        return new(chars);
+    }
+
+    public override bool Equals(object? obj)
+        => obj is kwum kw && kw == this;
+
+    public bool Equals(kwum other)
+        => other == this;
+
+    public override int GetHashCode()
+        => _value.GetHashCode();
+}