Restruct AppViewer codes

QuickLook.Plugin/QuickLook.Plugin.AppViewer/PackageParsers/Deb/ArReader.cs

@@ -0,0 +1,65 @@
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace QuickLook.Plugin.AppViewer.PackageParsers.Deb;
+
+public static class ArReader
+{
+    public static ArEntry[] Read(string filePath)
+    {
+        var entries = new List<ArEntry>();
+
+        using var fs = new FileStream(filePath, FileMode.Open, FileAccess.Read);
+        using var br = new BinaryReader(fs);
+
+        // Check ar magic
+        var magic = br.ReadBytes(8);
+        if (Encoding.ASCII.GetString(magic) != "!<arch>\n")
+            throw new InvalidDataException("Not a valid ar file");
+
+        while (fs.Position < fs.Length)
+        {
+            var header = br.ReadBytes(60);
+            if (header.Length < 60)
+                break;
+
+            string name = Encoding.ASCII.GetString(header, 0, 16).Trim();
+            string sizeStr = Encoding.ASCII.GetString(header, 48, 10).Trim();
+            string fmag = Encoding.ASCII.GetString(header, 58, 2);
+            if (fmag != "`\n")
+                throw new InvalidDataException("Invalid header end");
+
+            long size = long.Parse(sizeStr);
+
+            byte[] data = br.ReadBytes((int)size);
+
+            // Completion alignment: ar file is evenly aligned
+            if (size % 2 != 0)
+                br.ReadByte();
+
+            entries.Add(new ArEntry
+            {
+                FileName = name,
+                FileSize = size,
+                Data = data
+            });
+        }
+
+        return [.. entries];
+    }
+}
+
+public class ArEntry
+{
+    public string FileName { get; set; } = string.Empty;
+
+    public long FileSize { get; set; }
+
+    public byte[] Data { get; set; } = [];
+
+    public override string ToString()
+    {
+        return $"{FileName} ({FileSize})";
+    }
+}