Add romanised author & title fields

osu.Game/Beatmaps/MetadataUtils.cs

@@ -0,0 +1,47 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+#nullable enable
+
+using System.Linq;
+using System.Text;
+
+namespace osu.Game.Beatmaps
+{
+    /// <summary>
+    /// Groups utility methods used to handle beatmap metadata.
+    /// </summary>
+    public static class MetadataUtils
+    {
+        /// <summary>
+        /// Returns <see langword="true"/> if the character <paramref name="c"/> can be used in <see cref="BeatmapMetadata.Artist"/> and <see cref="BeatmapMetadata.Title"/> fields.
+        /// Characters not matched by this method can be placed in <see cref="BeatmapMetadata.ArtistUnicode"/> and <see cref="BeatmapMetadata.TitleUnicode"/>.
+        /// </summary>
+        public static bool IsRomanised(char c) => c <= 0xFF;
+
+        /// <summary>
+        /// Returns <see langword="true"/> if the string <paramref name="str"/> can be used in <see cref="BeatmapMetadata.Artist"/> and <see cref="BeatmapMetadata.Title"/> fields.
+        /// Strings not matched by this method can be placed in <see cref="BeatmapMetadata.ArtistUnicode"/> and <see cref="BeatmapMetadata.TitleUnicode"/>.
+        /// </summary>
+        public static bool IsRomanised(string? str) => str == null || str.All(IsRomanised);
+
+        /// <summary>
+        /// Returns a copy of <paramref name="str"/> with all characters that do not match <see cref="IsRomanised(char)"/> removed.
+        /// </summary>
+        public static string StripNonRomanisedCharacters(string? str)
+        {
+            if (string.IsNullOrEmpty(str))
+                return string.Empty;
+
+            var stringBuilder = new StringBuilder(str.Length);
+
+            foreach (var c in str)
+            {
+                if (IsRomanised(c))
+                    stringBuilder.Append(c);
+            }
+
+            return stringBuilder.ToString().Trim();
+        }
+    }
+}