feat: support Rune Princess archive

ArcFormats/ArcFormats.csproj

@@ -169,6 +169,7 @@
     <Compile Include="Macromedia\AudioSND.cs" />
     <Compile Include="Macromedia\DirectorFile.cs" />
     <Compile Include="Macromedia\Palettes.cs" />
+    <Compile Include="MAGES\ArcARC20.cs" />
     <Compile Include="Mugi\ArcBIN.cs" />
     <Compile Include="NScripter\Script.cs" />
     <Compile Include="Psp\ArcQPK.cs" />

ArcFormats/MAGES/ArcARC20.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.Composition;
+using System.Text;
+
+namespace GameRes.Formats.MAGES
+{
+    [Export(typeof(ArchiveFormat))]
+    public class ARC20Opener : ArchiveFormat
+    {
+        public override string Tag { get { return "ARC/Princess Soft ARC20"; } }
+        public override string Description { get { return "Princess Soft PS2 resource archive"; } }
+        public override uint Signature { get { return 0x20435241; } } // 'ARC\x20'
+        public override bool IsHierarchic { get { return false; } }
+        public override bool CanWrite { get { return false; } }
+
+        public override ArcFile TryOpen(ArcView file)
+        {
+            int count = file.View.ReadInt32(4);
+            if (!IsSaneCount(count))
+                return null;
+            uint filename_end = file.View.ReadUInt32(8);
+            var dir = new List<Entry>(count);
+            uint index_offset;
+            for (int i = 0; i < count; ++i)
+            {
+                index_offset = file.View.ReadUInt32(16 * i + 16);
+                byte c;
+                List<byte> namebyte = new List<byte>();
+                while (true) 
+                {
+                    c = file.View.ReadByte((long)index_offset);
+                    if (c == 0 | index_offset > filename_end) break;
+                    namebyte.Add(c);
+                    index_offset++;
+                }
+                var sjis = System.Text.Encoding.GetEncoding("Shift-JIS");
+                var name = sjis.GetString(namebyte.ToArray());
+                var entry = Create<PackedEntry>(name);
+                
+                entry.Offset = file.View.ReadUInt32(16 * i + 16 + 4) * 2048;
+
+                entry.Size = file.View.ReadUInt32(16 * i + 16 + 8);
+                entry.UnpackedSize = file.View.ReadUInt32(16 * i + 16 + 8);
+                if (!entry.CheckPlacement(file.MaxOffset))
+                    return null;
+                dir.Add(entry);
+            }
+            return new ArcFile(file, this, dir);
+        }
+    }
+}