Implement INPUTNAME string opcodes

2026-07-29 13:21:15 -04:00
parent 862b74ecbc
commit feef18d411
12 changed files with 443 additions and 4 deletions
--- a/engine/Age.Engine/Sys4/Cp932Text.cs
+++ b/engine/Age.Engine/Sys4/Cp932Text.cs
@@ -0,0 +1,98 @@
+using System.Text;
+
+namespace Age.Engine.Sys4;
+
+public enum FullwidthTextValidationError
+{
+    None,
+    TooLong,
+    NonDoubleByteCharacter,
+}
+
+/// <summary>AGE's Japanese-locale byte-string operations used by INPUTNAME.</summary>
+public static class Cp932Text
+{
+    public const int NativeNameByteLimit = 16;
+    private static readonly Encoding NativeEncoding;
+
+    static Cp932Text()
+    {
+        Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
+        NativeEncoding = Encoding.GetEncoding(932);
+    }
+
+    private static bool IsLeadByte(byte value)
+        => value is >= 0x81 and <= 0x9f or >= 0xe0 and <= 0xfc;
+
+    private static bool IsTrailByte(byte value)
+        => value is >= 0x40 and <= 0x7e or >= 0x80 and <= 0xfc;
+
+    private static byte[] EncodeCString(string value, Encoding encoding)
+    {
+        int nul = value.IndexOf('\0');
+        return encoding.GetBytes(nul < 0 ? value : value[..nul]);
+    }
+
+    public static int CharacterLength(string value, Encoding encoding)
+    {
+        byte[] bytes = EncodeCString(value, encoding);
+        int count = 0;
+        for (int offset = 0; offset < bytes.Length; count++)
+        {
+            if (IsLeadByte(bytes[offset]) && offset + 1 < bytes.Length
+                                          && IsTrailByte(bytes[offset + 1]))
+                offset += 2;
+            else
+                offset++;
+        }
+        return count;
+    }
+
+    public static string Substring(
+        string value, int start, int count, Encoding encoding)
+    {
+        byte[] bytes = EncodeCString(value, encoding);
+        var characters = new List<(int Offset, int Length)>();
+        for (int offset = 0; offset < bytes.Length;)
+        {
+            int length = IsLeadByte(bytes[offset]) && offset + 1 < bytes.Length
+                                                  && IsTrailByte(bytes[offset + 1])
+                ? 2
+                : 1;
+            characters.Add((offset, length));
+            offset += length;
+        }
+
+        int end = unchecked(start + count);
+        if (end < 1 || end > characters.Count) end = characters.Count;
+
+        using var selected = new MemoryStream();
+        for (int index = 0; index < characters.Count; index++)
+        {
+            if (index < start || index >= end) continue;
+            (int offset, int length) = characters[index];
+            selected.Write(bytes, offset, length);
+        }
+        return encoding.GetString(selected.ToArray());
+    }
+
+    public static FullwidthTextValidationError ValidateFullwidthName(
+        string value, Encoding encoding, int byteLimit = NativeNameByteLimit)
+    {
+        byte[] bytes = EncodeCString(value, encoding);
+        if (bytes.Length > byteLimit) return FullwidthTextValidationError.TooLong;
+
+        for (int offset = 0; offset < bytes.Length; offset += 2)
+        {
+            if (offset + 1 >= bytes.Length
+                || !IsLeadByte(bytes[offset])
+                || !IsTrailByte(bytes[offset + 1]))
+                return FullwidthTextValidationError.NonDoubleByteCharacter;
+        }
+        return FullwidthTextValidationError.None;
+    }
+
+    public static FullwidthTextValidationError ValidateFullwidthName(
+        string value, int byteLimit = NativeNameByteLimit)
+        => ValidateFullwidthName(value, NativeEncoding, byteLimit);
+}