IsValid() method performance improved ~10x. Tests fixed - alternative letters (like I instead of 1) should be allowed. (#11)

Author: Seramis

src/ByteAether.Ulid.Tests/Ulid.IsValid.cs

@@ -5,6 +5,7 @@ public class UlidIsValidTests
 	[Theory]
 	[InlineData("01AN4Z07BY79KA1307SR9X4MV3")]
 	[InlineData("00000000000000000000000000")]
+	[InlineData("oooooooooooooooooooooooooo")]
 	[InlineData("7ZZZZZZZZZZZZZZZZZZZZZZZZZ")]
 	public void IsValid_GoodString(string goodString)
 	{
@@ -21,7 +22,7 @@ public void IsValid_GoodString(string goodString)
 	[InlineData("")]
 	[InlineData("01AN4Z07BY79KA1307SR9X4MV")]
 	[InlineData("01AN4Z07BY79KA1307SR9X4MV3A")]
-	[InlineData("01AN4Z07BY79KA1307SR9X4MVI")]
+	[InlineData("01AN4Z07BY79KA1307SR9X4MVU")]
 	[InlineData("01AN4Z07BY79KA1307SR9X4MV@")]
 	public void IsValid_BadString(string badString)
 	{
@@ -35,6 +36,7 @@ public void IsValid_BadString(string badString)
 	[Theory]
 	[InlineData("01AN4Z07BY79KA1307SR9X4MV3")]
 	[InlineData("00000000000000000000000000")]
+	[InlineData("oooooooooooooooooooooooooo")]
 	[InlineData("7ZZZZZZZZZZZZZZZZZZZZZZZZZ")]
 	public void IsValid_GoodStringSpan(string goodString)
 	{
@@ -51,7 +53,7 @@ public void IsValid_GoodStringSpan(string goodString)
 	[InlineData("")]
 	[InlineData("01AN4Z07BY79KA1307SR9X4MV")]
 	[InlineData("01AN4Z07BY79KA1307SR9X4MV3A")]
-	[InlineData("01AN4Z07BY79KA1307SR9X4MVI")]
+	[InlineData("01AN4Z07BY79KA1307SR9X4MVU")]
 	[InlineData("01AN4Z07BY79KA1307SR9X4MV@")]
 	public void IsValid_BadStringSpan(string badString)
 	{

src/ByteAether.Ulid/Ulid.IsValid.cs

@@ -32,26 +32,15 @@ public static bool IsValid(ReadOnlySpan<char> ulidString)
 			return false;
 		}
 
-		// First character check
-		var isValidFirstChar = false;
-		for (var i = 7; i >= 0; --i)
-		{
-			if (ulidString[0] == _base32Chars[i])
-			{
-				isValidFirstChar = true;
-				break;
-			}
-		}
-
-		if (!isValidFirstChar)
+		var firstChar = ulidString[0];
+		if (_inverseBase32[firstChar] > 7)
 		{
 			return false;
 		}
 
-		// Rest of the characters check
-		foreach (var c in ulidString[1..])
+		for (var i = 1; i < UlidStringLength; i++)
 		{
-			if (!_base32Chars.Contains(c))
+			if (_inverseBase32[ulidString[i]] == 255)
 			{
 				return false;
 			}