Change Skin Material Replacement to accept arbitrary suffix-strings for From and To.

Penumbra/Util/ModelChanger.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Text;
@@ -9,10 +10,105 @@ namespace Penumbra.Util;
 
 public static class ModelChanger
 {
-    private const           string SkinMaterialString = "/mt_c0201b0001_d.mtrl";
+    private static int FindSubSequence( byte[] main, byte[] sub, int from = 0 )
-    private static readonly byte[] SkinMaterial       = Encoding.UTF8.GetBytes( SkinMaterialString );
+    {
+        if( sub.Length + from > main.Length )
+        {
+            return -1;
+        }
 
-    public static int ChangeMtrl( FullPath file, byte from, byte to )
+        var length = main.Length - sub.Length;
+        for( var i = from; i < length; ++i )
+        {
+            var span = main.AsSpan( i, sub.Length );
+            if( span.SequenceEqual( sub ) )
+            {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+
+    private static bool ConvertString( string text, out byte[] data )
+    {
+        data = Encoding.UTF8.GetBytes( text );
+        return data.Length == text.Length && !data.Any( b => b > 0b10000000 );
+    }
+
+    public static bool ValidStrings( string from, string to )
+        => from.Length                          != 0
+         && to.Length                           != 0
+         && from.Length                         < 16
+         && to.Length                           < 16
+         && from                                != to
+         && Encoding.UTF8.GetByteCount( from ) == from.Length
+         && Encoding.UTF8.GetByteCount( to )   == to.Length;
+
+    private static bool ConvertName( string name, out byte[] data )
+    {
+        if( name.Length != 0 )
+        {
+            return ConvertString( $"/mt_c0201b0001_{name}.mtrl", out data );
+        }
+
+        data = Array.Empty< byte >();
+        return false;
+    }
+
+    private static int ReplaceEqualSequences( byte[] main, byte[] subLhs, byte[] subRhs )
+    {
+        if( subLhs.SequenceEqual( subRhs ) )
+        {
+            return 0;
+        }
+
+        var i            = 0;
+        var replacements = 0;
+        while( ( i = FindSubSequence( main, subLhs, i ) ) > 0 )
+        {
+            subRhs.CopyTo( main.AsSpan( i ) );
+            i += subLhs.Length;
+            ++replacements;
+        }
+
+        return replacements;
+    }
+
+    private static int ReplaceSubSequences( ref byte[] main, byte[] subLhs, byte[] subRhs )
+    {
+        if( subLhs.Length == subRhs.Length )
+        {
+            return ReplaceEqualSequences( main, subLhs, subRhs );
+        }
+
+        var replacements = new List< int >( 4 );
+        for( var i = FindSubSequence( main, subLhs ); i >= 0; i = FindSubSequence( main, subLhs, i + subLhs.Length ) )
+        {
+            replacements.Add( i );
+        }
+
+        var ret = new byte[main.Length + ( subRhs.Length - subLhs.Length ) * replacements.Count];
+
+        var last        = 0;
+        var totalLength = 0;
+        foreach( var i in replacements )
+        {
+            var length = i - last;
+            main.AsSpan( last, length ).CopyTo( ret.AsSpan( totalLength ) );
+            totalLength += length;
+            subRhs.CopyTo( ret.AsSpan( totalLength ) );
+            totalLength += subRhs.Length;
+            last        =  i + subLhs.Length;
+        }
+
+        main.AsSpan( last ).CopyTo( ret.AsSpan( totalLength ) );
+
+        main = ret;
+        return replacements.Count;
+    }
+
+    public static int ChangeMtrl( FullPath file, byte[] from, byte[] to )
     {
         if( !file.Exists )
         {
@@ -22,53 +118,31 @@ public static class ModelChanger
         try
         {
             var text     = File.ReadAllBytes( file.FullName );
-            var replaced = 0;
+            var replaced = ReplaceSubSequences( ref text, from, to );
-
+            if( replaced > 0 )
-            var length = text.Length - SkinMaterial.Length;
-            SkinMaterial[ 15 ] = from;
-            for( var i = 0; i < length; ++i )
             {
-                if( SkinMaterial.Where( ( t, j ) => text[ i + j ] != t ).Any() )
+                File.WriteAllBytes( file.FullName, text );
-                {
-                    continue;
-                }
-
-                text[ i + 15 ] =  to;
-                i              += SkinMaterial.Length;
-                ++replaced;
             }
 
-            if( replaced == 0 )
-            {
-                return 0;
-            }
-
-            File.WriteAllBytes( file.FullName, text );
             return replaced;
         }
         catch( Exception e )
         {
-            PluginLog.Error( $"Could not write .mdl data for file {file.FullName}, replacing {( char )from} with {( char )to}:\n{e}" );
+            PluginLog.Error( $"Could not write .mdl data for file {file.FullName}:\n{e}" );
             return -1;
         }
     }
 
-    public static bool ChangeModMaterials( ModData mod, byte from, byte to )
+    public static bool ChangeModMaterials( ModData mod, string from, string to )
     {
-        return mod.Resources.ModFiles
+        if( ValidStrings( from, to ) && ConvertName( from, out var lhs ) && ConvertName( to, out var rhs ) )
-           .Where( f => f.Extension.Equals( ".mdl", StringComparison.InvariantCultureIgnoreCase ) )
+        {
-           .All( file => ChangeMtrl( file, from, to ) >= 0 );
+            return mod.Resources.ModFiles
+               .Where( f => f.Extension.Equals( ".mdl", StringComparison.InvariantCultureIgnoreCase ) )
+               .All( file => ChangeMtrl( file, lhs, rhs ) >= 0 );
+        }
+
+        PluginLog.Warning( $"{from} or {to} can not be valid material suffixes." );
+        return false;
     }
-
-    public static bool ChangeMtrlBToD( ModData mod )
-        => ChangeModMaterials( mod, ( byte )'b', ( byte )'d' );
-
-    public static bool ChangeMtrlDToB( ModData mod )
-        => ChangeModMaterials( mod, ( byte )'d', ( byte )'b' );
-
-    public static bool ChangeMtrlEToA( ModData mod )
-        => ChangeModMaterials( mod, ( byte )'e', ( byte )'a' );
-
-    public static bool ChangeMtrlAToE( ModData mod )
-        => ChangeModMaterials( mod, ( byte )'a', ( byte )'e' );
 }