Initial commit

.gitignore

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+### Windows template
+# Windows thumbnail cache files
+Thumbs.db
+Thumbs.db:encryptable
+ehthumbs.db
+ehthumbs_vista.db
+
+# Dump file
+*.stackdump
+
+# Folder config file
+[Dd]esktop.ini
+
+# Recycle Bin used on file shares
+$RECYCLE.BIN/
+
+# Windows Installer files
+*.cab
+*.msi
+*.msix
+*.msm
+*.msp
+
+# Windows shortcuts
+*.lnk
+
+### macOS template
+# General
+.DS_Store
+.AppleDouble
+.LSOverride
+
+# Icon must end with two \r
+Icon
+
+# Thumbnails
+._*
+
+# Files that might appear in the root of a volume
+.DocumentRevisions-V100
+.fseventsd
+.Spotlight-V100
+.TemporaryItems
+.Trashes
+.VolumeIcon.icns
+.com.apple.timemachine.donotpresent
+
+# Directories potentially created on remote AFP share
+.AppleDB
+.AppleDesktop
+Network Trash Folder
+Temporary Items
+.apdisk
+
+# JetBrains
+.idea/
+
+# Visual Studio
+.vs/
+bin/
+obj/
+
+# Visual Studio Code
+.vscode/
+

LCRng.cs

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+namespace PCDWC4Converter;
+
+public class LCRng
+{
+    private uint _seed;
+
+    public LCRng(uint seed = 0) => _seed = seed;
+
+    public uint Next() => _seed = _seed * 0x41C64E6Du + 0x00006073u;
+
+    public uint NextH() => Next() >> 0x10;
+
+    public uint Prev() => _seed = _seed * 0xEEB9EB65u + 0xA3561A1u;
+    
+    public uint PrevH() => Prev() >> 0x10;
+}

PCDWC4Converter.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net6.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+</Project>

PCDWC4Converter.sln

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+
+Microsoft Visual Studio Solution File, Format Version 12.00
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "PCDWC4Converter", "PCDWC4Converter.csproj", "{CAED887B-C68C-4EF4-9897-BA1D25ECBC89}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{CAED887B-C68C-4EF4-9897-BA1D25ECBC89}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{CAED887B-C68C-4EF4-9897-BA1D25ECBC89}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{CAED887B-C68C-4EF4-9897-BA1D25ECBC89}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{CAED887B-C68C-4EF4-9897-BA1D25ECBC89}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal

PokemonData.cs

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+using System.Buffers.Binary;
+
+namespace PCDWC4Converter;
+
+public static class PokemonData
+{
+    private static readonly int[][] _blockPositions =
+    {
+        new[] { 0, 0, 0, 0, 0, 0, 1, 1, 2, 3, 2, 3, 1, 1, 2, 3, 2, 3, 1, 1, 2, 3, 2, 3 },
+        new[] { 1, 1, 2, 3, 2, 3, 0, 0, 0, 0, 0, 0, 2, 3, 1, 1, 3, 2, 2, 3, 1, 1, 3, 2 },
+        new[] { 2, 3, 1, 1, 3, 2, 2, 3, 1, 1, 3, 2, 0, 0, 0, 0, 0, 0, 3, 2, 3, 2, 1, 1 },
+        new[] { 3, 2, 3, 2, 1, 1, 3, 2, 3, 2, 1, 1, 3, 2, 3, 2, 1, 1, 0, 0, 0, 0, 0, 0 },
+    };
+
+    private static void XorCrypt(Span<byte> data)
+    {
+        var pid = BinaryPrimitives.ReadUInt32LittleEndian(data[..4]);
+        var initialSeed = BinaryPrimitives.ReadUInt16LittleEndian(data[6..8]);
+
+        var rng = new LCRng(initialSeed);
+
+        for (var i = 8; i < 236; i += 2)
+        {
+            if (i == 136)
+            {
+                rng = new LCRng(pid);
+            }
+
+            var dataBlock = data[i..];
+            var value = BinaryPrimitives.ReadUInt16LittleEndian(dataBlock);
+            BinaryPrimitives.WriteUInt16LittleEndian(dataBlock, (ushort)(value ^ rng.NextH()));
+        }
+    }
+
+    private static void Unshuffle(Span<byte> data)
+    {
+        var pid = BinaryPrimitives.ReadUInt32LittleEndian(data[..4]);
+        var shiftValue = ((pid & 0x3E000) >> 0xD) % 24;
+
+        // Offset by first block
+        data = data.Slice(8, 32 * 4);
+
+        Span<byte> originalData = stackalloc byte[32 * 4];
+        data.CopyTo(originalData);
+        
+        for (var i = 0; i < 4; i++)
+        {
+            // Unshuffle the data
+            originalData.Slice(32 * _blockPositions[i][shiftValue], 32).CopyTo(data);
+            
+            // Increment to next block
+            data = data[32..];
+        }
+    }
+    
+    private static void Shuffle(Span<byte> data)
+    {
+        var pid = BinaryPrimitives.ReadUInt32LittleEndian(data[..4]);
+        var shiftValue = ((pid & 0x3E000) >> 0xD) % 24;
+
+        // Offset by first block
+        data = data.Slice(8, 32 * 4);
+
+        Span<byte> originalData = stackalloc byte[32 * 4];
+        data.CopyTo(originalData);
+        
+        for (var i = 0; i < 4; i++)
+        {
+            // Shuffle the data
+            originalData[..32].CopyTo(data.Slice(_blockPositions[i][shiftValue], 32));
+            
+            // Increment to next block
+            originalData = originalData[32..];
+        }
+    }
+
+    public static void DecryptData(Span<byte> pkmData)
+    {
+        XorCrypt(pkmData);
+        Unshuffle(pkmData);
+    }
+
+    public static void EncryptData(Span<byte> pkmData)
+    {
+        XorCrypt(pkmData);
+        Shuffle(pkmData);
+    }
+}

Program.cs

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+using PCDWC4Converter;
+
+Console.WriteLine("PCDWC4Converter v1.0 by Sabresite");
+
+if (args.Length == 0)
+{
+    Console.WriteLine("Usage: ./pcdwc4converter <path-to-folder-or-file>");
+    return;
+}
+
+var path = args[0];
+var fileAttr = File.GetAttributes(path);
+
+var extensions = new [] { ".pcd", ".wc4" };
+var files = Array.Empty<FileInfo>();
+
+if ((fileAttr & FileAttributes.Directory) != 0)
+{
+    files = Directory.GetFiles(path, "*.*", SearchOption.AllDirectories)
+        .Select(file => new FileInfo(file))
+        .Where(file => extensions.Contains(file.Extension) && file.Length == 856)
+        .ToArray();
+}
+else if (File.Exists(path))
+{
+    var file = new FileInfo(path);
+    if (extensions.Contains(file.Extension) && file.Length == 856)
+    {
+        files = new[] { file };
+    }
+}
+
+if (files.Length == 0)
+{
+    Console.WriteLine("No files found to convert.");
+    return;
+}
+
+// All PCD data
+Span<byte> fileData = stackalloc byte[856];
+
+for (var i = 0; i < files.Length; i++)
+{
+    var file = files[i];
+    using (var fs = file.OpenRead())
+    {
+        var bytesRead = fs.Read(fileData);
+        if (bytesRead != 856)
+        {
+            Console.WriteLine("Failed to read file {0}", file.FullName);
+            continue;
+        }
+    }
+
+    var newExtension = "";
+
+    switch (file.Extension)
+    {
+        case ".pcd":
+            {
+                PokemonData.DecryptData(fileData[8..]);
+                newExtension = ".wc4";
+                break;
+            }
+        case ".wc4":
+            {
+                PokemonData.EncryptData(fileData[8..]);
+                newExtension = ".pcd";
+                break;
+            }
+    }
+
+    var newFilePath = Path.Join(file.DirectoryName, $"{file.Name[..^file.Extension.Length]}{newExtension}");
+    Console.WriteLine("New File {0}", newFilePath);
+    try
+    {
+        File.Delete(newFilePath);
+        using var writer = new FileStream(newFilePath, FileMode.Create, FileAccess.Write, FileShare.None);
+        writer.Write(fileData);
+    }
+    catch (Exception e)
+    {
+        Console.WriteLine("Failed to write file {0}", newFilePath);
+        Console.WriteLine(e);
+    }
+}

README.md

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-# PCDWC4Converter
-Converter for PCD<->WC4
+# PCD/WC4 Converter for Pokemon Gen 4 Wondercards
+
+## Requirements
+* .NET 6
+
+### Usage
+```bash
+./pcdwc4converter <path-to-folder-or-file>
+```
+
+## Building Solution
+* .NET 6 SDK
+* Visual Studio 2022 or Rider 2021.3+