Implement readdir for Opera.

DiscImageChef.Filesystems/Opera/Dir.cs

@@ -1,5 +1,7 @@
 using System;
 using System.Collections.Generic;
+using System.Globalization;
+using System.Linq;
 using DiscImageChef.CommonTypes.Structs;
 using DiscImageChef.Helpers;
 
@@ -7,7 +9,62 @@ namespace DiscImageChef.Filesystems
 {
     public partial class OperaFS
     {
-        public Errno ReadDir(string path, out List<string> contents) => throw new NotImplementedException();
+        public Errno ReadDir(string path, out List<string> contents)
+        {
+            contents = null;
+            if(!mounted) return Errno.AccessDenied;
+
+            if(string.IsNullOrWhiteSpace(path) || path == "/")
+            {
+                contents = rootDirectoryCache.Keys.ToList();
+                return Errno.NoError;
+            }
+
+            string cutPath = path.StartsWith("/", StringComparison.Ordinal)
+                                 ? path.Substring(1).ToLower(CultureInfo.CurrentUICulture)
+                                 : path.ToLower(CultureInfo.CurrentUICulture);
+
+            if(directoryCache.TryGetValue(cutPath, out Dictionary<string, DirectoryEntryWithPointers> currentDirectory))
+            {
+                contents = currentDirectory.Keys.ToList();
+                return Errno.NoError;
+            }
+
+            string[] pieces = cutPath.Split(new[] {'/'}, StringSplitOptions.RemoveEmptyEntries);
+
+            KeyValuePair<string, DirectoryEntryWithPointers> entry =
+                rootDirectoryCache.FirstOrDefault(t => t.Key.ToLower(CultureInfo.CurrentUICulture) == pieces[0]);
+
+            if(string.IsNullOrEmpty(entry.Key)) return Errno.NoSuchFile;
+
+            if((entry.Value.entry.flags & FLAGS_MASK) != (int)FileFlags.Directory) return Errno.NotDirectory;
+
+            string currentPath = pieces[0];
+
+            currentDirectory = rootDirectoryCache;
+
+            for(int p = 0; p < pieces.Length; p++)
+            {
+                entry = currentDirectory.FirstOrDefault(t => t.Key.ToLower(CultureInfo.CurrentUICulture) == pieces[p]);
+
+                if(string.IsNullOrEmpty(entry.Key)) return Errno.NoSuchFile;
+
+                if((entry.Value.entry.flags & FLAGS_MASK) != (int)FileFlags.Directory) return Errno.NotDirectory;
+
+                currentPath = p == 0 ? pieces[0] : $"{currentPath}/{pieces[p]}";
+
+                if(directoryCache.TryGetValue(currentPath, out currentDirectory)) continue;
+
+                if(entry.Value.pointers.Length < 1) return Errno.InvalidArgument;
+
+                currentDirectory = DecodeDirectory((int)entry.Value.pointers[0]);
+
+                directoryCache.Add(currentPath, currentDirectory);
+            }
+
+            contents = currentDirectory?.Keys.ToList();
+            return Errno.NoError;
+        }
 
         Dictionary<string, DirectoryEntryWithPointers> DecodeDirectory(int firstBlock)
         {