Optimizing enumeration

.gitignore

@@ -361,3 +361,5 @@ MigrationBackup/
 
 # Fody - auto-generated XML schema
 FodyWeavers.xsd
+
+/Files/db.db

Files/ByteSize.cs

@@ -0,0 +1,396 @@
+using System;
+using System.Globalization;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+
+#nullable enable
+
+namespace Files
+{
+    public readonly partial struct ByteSize : IEquatable<ByteSize>, IComparable<ByteSize>
+    {
+        public static readonly ByteSize MinValue = new ByteSize(long.MinValue);
+        public static readonly ByteSize MaxValue = new ByteSize(long.MaxValue);
+        public static readonly ByteSize ZeroValue = new ByteSize(0);
+
+        public static ByteSize operator +(ByteSize b1, ByteSize b2) => new ByteSize(b1._bytes + b2._bytes);
+        public static ByteSize operator +(ByteSize b1, long b2) => new ByteSize(b1._bytes + b2);
+        public static ByteSize operator +(ByteSize b1, int b2) => new ByteSize(b1._bytes + b2);
+        public static ByteSize operator ++(ByteSize b) => new ByteSize(b._bytes + 1);
+        public static ByteSize operator -(ByteSize b) => new ByteSize(-b._bytes);
+        public static ByteSize operator -(ByteSize b1, ByteSize b2) => new ByteSize(b1._bytes - b2._bytes);
+        public static ByteSize operator -(ByteSize b1, long b2) => new ByteSize(b1._bytes - b2);
+        public static ByteSize operator -(ByteSize b1, int b2) => new ByteSize(b1._bytes - b2);
+        public static ByteSize operator --(ByteSize b) => new ByteSize(b._bytes - 1);
+        public static bool operator ==(ByteSize b1, ByteSize b2) => b1._bytes == b2._bytes;
+        public static bool operator !=(ByteSize b1, ByteSize b2) => b1._bytes != b2._bytes;
+        public static bool operator <(ByteSize b1, ByteSize b2) => b1._bytes < b2._bytes;
+        public static bool operator <=(ByteSize b1, ByteSize b2) => b1._bytes <= b2._bytes;
+        public static bool operator >(ByteSize b1, ByteSize b2) => b1._bytes > b2._bytes;
+        public static bool operator >=(ByteSize b1, ByteSize b2) => b1._bytes >= b2._bytes;
+        public static implicit operator ByteSize(long bytes) => new ByteSize(bytes);
+        public static implicit operator ByteSize(int bytes) => new ByteSize(bytes);
+        public static implicit operator ByteSize(string text) => Parse(text, CultureInfo.CurrentCulture);
+        public static implicit operator long(ByteSize bytes) => bytes._bytes;
+        public static explicit operator int(ByteSize bytes) => (int)bytes._bytes;
+        public static implicit operator string(ByteSize bytes) => bytes.ToString();
+
+        private readonly long _bytes;
+
+        private ByteSize(long bytes)
+        {
+            _bytes = bytes;
+        }
+
+        public ByteSize Add(ByteSize bs) => new ByteSize(_bytes + bs._bytes);
+
+        public ByteSize AddBytes(long value) => new ByteSize(_bytes + value);
+
+        public int CompareTo(ByteSize other) => _bytes.CompareTo(other._bytes);
+
+        public bool Equals(ByteSize other) => _bytes == other._bytes;
+
+        public override bool Equals(object? obj) => obj is ByteSize other && Equals(other);
+
+        public override int GetHashCode() => _bytes.GetHashCode();
+
+        public override string ToString() =>
+            ToStringWithDecimalPrefixedUnitName("0.##");
+
+        public string ToString(string? format) =>
+            ToStringWithDecimalPrefixedUnitName(format);
+
+        public string ToString(IFormatProvider? provider) =>
+            ToStringWithDecimalPrefixedUnitName(provider: provider);
+
+        public string ToString(string? format, IFormatProvider? provider) =>
+            ToStringWithDecimalPrefixedUnitName(format, provider);
+
+        public string ToString(string? format, IFormatProvider? provider, bool useBinaryUnitNamePrefix)
+        {
+            return useBinaryUnitNamePrefix
+                ? ToStringWithBinaryPrefixedUnitName(format, provider)
+                : ToStringWithDecimalPrefixedUnitName(format, provider);
+        }
+
+        public string ToString(string? format, IFormatProvider? provider, bool useBinaryUnitNamePrefix, bool useShortUnitName)
+        {
+            return useBinaryUnitNamePrefix
+                ? ToStringWithBinaryPrefixedUnitName(format, provider, useShortUnitName)
+                : ToStringWithDecimalPrefixedUnitName(format, provider, useShortUnitName);
+        }
+    }
+
+    public readonly partial struct ByteSize
+    {
+        private const long _oneKibiByte = 1024;
+        private const long _oneMebiByte = 1024 * _oneKibiByte;
+        private const long _oneGibiByte = 1024 * _oneMebiByte;
+        private const long _oneTebiByte = 1024 * _oneGibiByte;
+        private const long _onePebiByte = 1024 * _oneTebiByte;
+        private const long _oneExbiByte = 1024 * _onePebiByte;
+
+        public static ByteSize FromKibiBytes(double value) => new ByteSize((long)(value * _oneKibiByte));
+
+        public static ByteSize FromMebiBytes(double value) => new ByteSize((long)(value * _oneMebiByte));
+
+        public static ByteSize FromGibiBytes(double value) => new ByteSize((long)(value * _oneGibiByte));
+
+        public static ByteSize FromTebiBytes(double value) => new ByteSize((long)(value * _oneTebiByte));
+
+        public static ByteSize FromPebiBytes(double value) => new ByteSize((long)(value * _onePebiByte));
+
+        public ByteSize AddKibiBytes(double value) => new ByteSize((long)(value * _oneKibiByte) + _bytes);
+
+        public ByteSize AddMebiBytes(double value) => new ByteSize((long)(value * _oneMebiByte) + _bytes);
+
+        public ByteSize AddGibiBytes(double value) => new ByteSize((long)(value * _oneGibiByte) + _bytes);
+
+        public ByteSize AddTebiBytes(double value) => new ByteSize((long)(value * _oneTebiByte) + _bytes);
+
+        public ByteSize AddPebiBytes(double value) => new ByteSize((long)(value * _onePebiByte) + _bytes);
+
+        public double AsKibiBytes => (double)_bytes / _oneKibiByte;
+
+        public double AsMebiBytes => (double)_bytes / _oneMebiByte;
+
+        public double AsGibiBytes => (double)_bytes / _oneGibiByte;
+
+        public double AsTebiBytes => (double)_bytes / _oneTebiByte;
+
+        public double AsPebiBytes => (double)_bytes / _onePebiByte;
+
+        public string ToStringWithBinaryPrefixedShortUnitName(string? format = null, IFormatProvider? provider = null) =>
+            ToStringWithBinaryPrefixedUnitName(format, provider, true);
+
+        public string ToStringWithBinaryPrefixedLongUnitName(string? format = null, IFormatProvider? provider = null) =>
+            ToStringWithBinaryPrefixedUnitName(format, provider, false);
+
+        public string ToStringWithBinaryPrefixedUnitName(string? format = null, IFormatProvider? provider = null, bool useShortUnitName = true)
+        {
+            provider ??= CultureInfo.CurrentCulture;
+
+            return _bytes switch
+            {
+                var b when b >= _oneExbiByte =>
+                    (b / (double)_oneExbiByte).ToString(format, provider) + (useShortUnitName ? " EiB" : b == _oneExbiByte ? " exbibyte" : " exbibytes"),
+                var b when b >= _onePebiByte =>
+                    (b / (double)_onePebiByte).ToString(format, provider) + (useShortUnitName ? " PiB" : b == _onePebiByte ? " pebibyte" : " pebibytes"),
+                var b when b >= _oneTebiByte =>
+                    (b / (double)_oneTebiByte).ToString(format, provider) + (useShortUnitName ? " TiB" : b == _oneTebiByte ? " tebibyte" : " tebibytes"),
+                var b when b >= _oneGibiByte =>
+                    (b / (double)_oneGibiByte).ToString(format, provider) + (useShortUnitName ? " GiB" : b == _oneGibiByte ? " gibibyte" : " gibibytes"),
+                var b when b >= _oneMebiByte =>
+                    (b / (double)_oneMebiByte).ToString(format, provider) + (useShortUnitName ? " MiB" : b == _oneMebiByte ? " mebibyte" : " mebibytes"),
+                var b when b >= _oneKibiByte =>
+                    (b / (double)_oneKibiByte).ToString(format, provider) + (useShortUnitName ? " KiB" : b == _oneKibiByte ? " kibibyte" : " kibibytes"),
+                var b =>
+                    b.ToString(format, provider) + (useShortUnitName ? " B" : b == 1 ? " byte" : " bytes")
+            };
+        }
+    }
+
+    public readonly partial struct ByteSize
+    {
+        private const long _oneKiloByte = 1000;
+        private const long _oneMegaByte = 1000 * _oneKiloByte;
+        private const long _oneGigaByte = 1000 * _oneMegaByte;
+        private const long _oneTeraByte = 1000 * _oneGigaByte;
+        private const long _onePetaByte = 1000 * _oneTeraByte;
+        private const long _oneExaByte = 1000 * _onePetaByte;
+
+        public static ByteSize FromKiloBytes(double value) => new ByteSize((long)(value * _oneKiloByte));
+
+        public static ByteSize FromMegaBytes(double value) => new ByteSize((long)(value * _oneMegaByte));
+
+        public static ByteSize FromGigaBytes(double value) => new ByteSize((long)(value * _oneGigaByte));
+
+        public static ByteSize FromTeraBytes(double value) => new ByteSize((long)(value * _oneTeraByte));
+
+        public static ByteSize FromPetaBytes(double value) => new ByteSize((long)(value * _onePetaByte));
+
+        public ByteSize AddKiloBytes(double value) => new ByteSize((long)(value * _oneKiloByte) + _bytes);
+
+        public ByteSize AddMegaBytes(double value) => new ByteSize((long)(value * _oneMegaByte) + _bytes);
+
+        public ByteSize AddGigaBytes(double value) => new ByteSize((long)(value * _oneGigaByte) + _bytes);
+
+        public ByteSize AddTeraBytes(double value) => new ByteSize((long)(value * _oneTeraByte) + _bytes);
+
+        public ByteSize AddPetaBytes(double value) => new ByteSize((long)(value * _onePetaByte) + _bytes);
+
+        public double AsKiloBytes => (double)_bytes / _oneKiloByte;
+
+        public double AsMegaBytes => (double)_bytes / _oneMegaByte;
+
+        public double AsGigaBytes => (double)_bytes / _oneGigaByte;
+
+        public double AsTeraBytes => (double)_bytes / _oneTeraByte;
+
+        public double AsPetaBytes => (double)_bytes / _onePetaByte;
+
+        public string ToStringWithDecimalPrefixedShortUnitName(string? format = null, IFormatProvider? provider = null) =>
+            ToStringWithDecimalPrefixedUnitName(format, provider, true);
+
+        public string ToStringWithDecimalPrefixedLongUnitName(string? format = null, IFormatProvider? provider = null) =>
+            ToStringWithDecimalPrefixedUnitName(format, provider, true);
+
+        public string ToStringWithDecimalPrefixedUnitName(string? format = null, IFormatProvider? provider = null, bool useShortUnitName = true)
+        {
+            provider ??= CultureInfo.CurrentCulture;
+
+            return _bytes switch
+            {
+                var b when b >= _oneExaByte =>
+                    (b / (double)_oneExaByte).ToString(format, provider) + (useShortUnitName ? " EB" : b == _oneExaByte ? " exabyte" : " exabytes"),
+                var b when b >= _onePetaByte =>
+                    (b / (double)_onePetaByte).ToString(format, provider) + (useShortUnitName ? " PB" : b == _onePetaByte ? " petabyte" : " petabytes"),
+                var b when b >= _oneTeraByte =>
+                    (b / (double)_oneTeraByte).ToString(format, provider) + (useShortUnitName ? " TB" : b == _oneTeraByte ? " terabyte" : " terabytes"),
+                var b when b >= _oneGigaByte =>
+                    (b / (double)_oneGigaByte).ToString(format, provider) + (useShortUnitName ? " GB" : b == _oneGigaByte ? " gigabyte" : " gigabytes"),
+                var b when b >= _oneMegaByte =>
+                    (b / (double)_oneMegaByte).ToString(format, provider) + (useShortUnitName ? " MB" : b == _oneMegaByte ? " megabyte" : " megabytes"),
+                var b when b >= _oneKiloByte =>
+                    (b / (double)_oneKiloByte).ToString(format, provider) + (useShortUnitName ? " kB" : b == _oneKiloByte ? " kilobyte" : " kilobytes"),
+                var b =>
+                b.ToString(format, provider) + (useShortUnitName ? " B" : b == 1 ? " byte" : " bytes")
+            };
+        }
+    }
+
+    public readonly partial struct ByteSize
+    {
+        public static readonly Dictionary<string, long> DefaultMatchesForUnitsOfMeasure =
+            new Dictionary<string, long>(StringComparer.OrdinalIgnoreCase)
+            {
+                ["kb"] = _oneKiloByte,
+                ["kilobyte"] = _oneKiloByte,
+                ["kilobytes"] = _oneKiloByte,
+
+                ["kib"] = _oneKibiByte,
+                ["kibibyte"] = _oneKibiByte,
+                ["kibibytes"] = _oneKibiByte,
+
+                ["mb"] = _oneMegaByte,
+                ["megabyte"] = _oneMegaByte,
+                ["megabytes"] = _oneMegaByte,
+
+                ["mib"] = _oneMebiByte,
+                ["mebibyte"] = _oneMebiByte,
+                ["mebibytes"] = _oneMebiByte,
+
+                ["gb"] = _oneGigaByte,
+                ["gigabyte"] = _oneGigaByte,
+                ["gigabytes"] = _oneGigaByte,
+
+                ["gib"] = _oneGibiByte,
+                ["gibibyte"] = _oneGibiByte,
+                ["gibibytes"] = _oneGibiByte,
+
+                ["tb"] = _oneTeraByte,
+                ["terabyte"] = _oneTeraByte,
+                ["terabytes"] = _oneTeraByte,
+
+                ["tib"] = _oneTebiByte,
+                ["tebibyte"] = _oneTebiByte,
+                ["tebibytes"] = _oneTebiByte,
+
+                ["pb"] = _onePetaByte,
+                ["petabyte"] = _onePetaByte,
+                ["petabytes"] = _onePetaByte,
+
+                ["pib"] = _onePebiByte,
+                ["pebibyte"] = _onePebiByte,
+                ["pebibytes"] = _onePebiByte,
+
+                ["eb"] = _oneExaByte,
+                ["exabyte"] = _oneExaByte,
+                ["exabytes"] = _oneExaByte,
+
+                ["eib"] = _oneExbiByte,
+                ["exbibyte"] = _oneExbiByte,
+                ["exbibytes"] = _oneExbiByte,
+            };
+
+        public static bool TryParse(string s, out ByteSize size) =>
+            TryParse(s.AsSpan(), CultureInfo.CurrentCulture, out size, DefaultMatchesForUnitsOfMeasure);
+
+        public static bool TryParse(string s, IFormatProvider provider, out ByteSize size) =>
+            TryParse(s.AsSpan(), provider, out size, DefaultMatchesForUnitsOfMeasure);
+
+        public static bool TryParse(string s, IFormatProvider provider, out ByteSize size,
+            IDictionary<string, long> unitsOfMeasure) =>
+            TryParse(s.AsSpan(), provider, out size, unitsOfMeasure);
+
+        public static bool TryParse(ReadOnlySpan<char> span, IFormatProvider provider, out ByteSize size, IDictionary<string, long> unitsOfMeasure)
+        {
+            ReadOnlySpan<char> trimmedFromStart = SkipWhitespace(span);
+            ReadOnlySpan<char> doublePart = TakeUntilWhitespace(trimmedFromStart, out ReadOnlySpan<char> afterDouble);
+
+            ReadOnlySpan<char> unitPart = TakeUntilWhitespace(SkipWhitespace(afterDouble), out _);
+
+            if (!double.TryParse(doublePart.ToString(), NumberStyles.Any, provider, out var parsedDouble))
+            {
+                size = ZeroValue;
+                return false;
+            }
+
+            string unit = unitPart.ToString();
+            long multiplier;
+
+            if (unitsOfMeasure.ContainsKey(unit))
+            {
+                multiplier = unitsOfMeasure[unit];
+            }
+            else if (string.IsNullOrEmpty(unit))
+            {
+                multiplier = 1;
+            }
+            else
+            {
+                size = ZeroValue;
+                return false;
+            }
+
+            size = (long)(parsedDouble * multiplier);
+            return true;
+        }
+
+
+        public static ByteSize Parse(string text) =>
+            Parse(text.AsSpan(), CultureInfo.CurrentCulture, DefaultMatchesForUnitsOfMeasure);
+
+        public static ByteSize Parse(string text, IFormatProvider provider) =>
+            Parse(text.AsSpan(), provider, DefaultMatchesForUnitsOfMeasure);
+
+        public static ByteSize Parse(string text, IFormatProvider provider, IDictionary<string, long> unitsOfMeasure) =>
+            Parse(text.AsSpan(), provider, unitsOfMeasure);
+
+        public static ByteSize Parse(ReadOnlySpan<char> span, IFormatProvider provider, IDictionary<string, long> unitsOfMeasure)
+        {
+            ReadOnlySpan<char> trimmedFromStart = SkipWhitespace(span);
+            ReadOnlySpan<char> doublePart = TakeUntilWhitespace(trimmedFromStart, out ReadOnlySpan<char> afterDouble);
+
+            var doubleValue = double.Parse(doublePart.ToString(), provider);
+
+            ReadOnlySpan<char> unitPart = TakeUntilWhitespace(SkipWhitespace(afterDouble), out _);
+
+            string unit = unitPart.ToString();
+            long multiplier;
+
+            if (unitsOfMeasure.ContainsKey(unit))
+            {
+                multiplier = unitsOfMeasure[unit];
+            }
+            else if (string.IsNullOrEmpty(unit))
+            {
+                multiplier = 1;
+            }
+            else
+            {
+                throw new ArgumentException("Unknown unit.", nameof(span));
+            }
+
+            return (long)(doubleValue * multiplier);
+        }
+
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static ReadOnlySpan<char> SkipWhitespace(ReadOnlySpan<char> chars)
+        {
+            int start = 0;
+            for (int i = 0; i < chars.Length; i++)
+            {
+                if (char.IsWhiteSpace(chars[i]))
+                {
+                    start++;
+                }
+                else
+                {
+                    return chars.Slice(start, chars.Length - start);
+                }
+            }
+
+            return ReadOnlySpan<char>.Empty;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static ReadOnlySpan<char> TakeUntilWhitespace(ReadOnlySpan<char> chars, out ReadOnlySpan<char> rest)
+        {
+            for (int i = 0; i < chars.Length; i++)
+            {
+                if (char.IsWhiteSpace(chars[i]))
+                {
+                    rest = chars.Slice(i);
+                    return chars.Slice(0, i);
+                }
+            }
+
+            rest = ReadOnlySpan<char>.Empty;
+            return chars;
+        }
+    }
+}
+
+#nullable restore

Files/Program.cs

@@ -10,68 +10,97 @@ using System.CommandLine.Invocation;
 using System.CommandLine.Parsing;
 using System.Threading.Tasks;
 using System.Linq;
+using System.Reflection;
+using System.Reflection.Emit;
 using Dapper;
-using System.Security.Cryptography;
+using Mono.Unix.Native;
 
-namespace Files {
-    class Program {
-        private static async Task IndexFiles(bool isVerbose, DirectoryInfo startDirectory, CancellationToken ct) {
+namespace Files
+{
+    class Program
+    {
+        private static async Task IndexFiles(Configuration configuration, CancellationToken ct)
+        {
             await AnsiConsole.Status()
-                .StartAsync("Thinking...", async ctx => {
-                    using var connection = new SqliteConnection("Data Source=db.db");
+                .StartAsync("Thinking...", async ctx =>
+                {
+                    await using var connection = new SqliteConnection("Data Source=db.db");
                     connection.Open();
-                    await using var transaction = await connection.BeginTransactionAsync();
+                    await using var transaction = await connection.BeginTransactionAsync(ct);
 
-                    var cnt = connection.ExecuteScalar<int>("SELECT count(*) FROM sqlite_master WHERE type='table' AND name=@tableName;", new { tableName = "files" });
-                    if (cnt == 0) 
+                    await InitializeDb(connection);
+
+                    if (!configuration.SkipFileScanning)
                     {
-                        connection.Execute("CREATE TABLE IF NOT EXISTS files (name TEXT, size INTEGER, inode INTEGER);");
-                    }
+                        Stack<string> directoriesStack = new Stack<string>();
+                        directoriesStack.Push(configuration.InitialDirectory?.ToString() ?? ".");
 
-                    Queue<string> directoriesQueue = new Queue<string>();
-                    directoriesQueue.Enqueue(startDirectory?.ToString() ?? ".");
+                        try
+                        {
+                            while (directoriesStack.TryPop(out string peekedDir))
+                            {
+                                string safePeekedDir = peekedDir.Replace("[", "[[").Replace("]", "]]");
+                                ctx.Status(safePeekedDir);
 
-                    try {
-                        while (directoriesQueue.TryDequeue(out string peekedDir)) {
-                            ctx.Status(peekedDir.Replace("[", "[[").Replace("]", "]]"));
-
-                            UnixDirectoryInfo dirInfo = new(peekedDir);
-                            if (!dirInfo.CanAccess(Mono.Unix.Native.AccessModes.R_OK)
-                            || !dirInfo.CanAccess(Mono.Unix.Native.AccessModes.X_OK)) {
-                                AnsiConsole.MarkupLine($"[red]:cross_mark: NO_ACCESS:[/] :file_folder: {dirInfo.ToString().Replace("[", "[[").Replace("]", "]]")}");
-                                return;
-                            }
-                            UnixFileSystemInfo[] entries = dirInfo.GetFileSystemEntries();
-                            foreach (UnixFileSystemInfo entry in entries) {
-                                string relativePath = Path.Combine(peekedDir, entry.Name);
-                                if (!entry.CanAccess(Mono.Unix.Native.AccessModes.R_OK)) {
-                                    if (entry.IsDirectory)
-                                        AnsiConsole.MarkupLine($"[red]:cross_mark: NO_ACCESS:[/] :file_folder: {relativePath.Replace("[", "[[").Replace("]", "]]")}");
-                                    else if (entry.IsRegularFile)
-                                        AnsiConsole.MarkupLine($"[red]:cross_mark: NO_ACCESS:[/] :page_facing_up: {relativePath.Replace("[", "[[").Replace("]", "]]")}");
-                                    continue;
-                                }
-
-                                if (entry.IsDirectory) {
-                                    directoriesQueue.Enqueue(relativePath);
-                                    continue;
-                                }
-
-                                connection.Execute("INSERT INTO files (name, size, inode) VALUES (@name, @Length, @Inode);", new { name = relativePath, entry.Length, entry.Inode });
-
-                                if (isVerbose)
-                                    AnsiConsole.MarkupLine($"[green]:check_mark: OK:[/] {relativePath.Replace("[", "[[").Replace("]", "]]")}");
-
-                                if (ct.IsCancellationRequested)
+                                UnixDirectoryInfo dirInfo = new(peekedDir);
+                                if (!dirInfo.CanAccess(Mono.Unix.Native.AccessModes.R_OK)
+                                || !dirInfo.CanAccess(Mono.Unix.Native.AccessModes.X_OK))
+                                {
+                                    AnsiConsole.MarkupLine($"[red]:cross_mark: NO_ACCESS:[/] :file_folder: {dirInfo.ToString().Replace("[", "[[").Replace("]", "]]")}");
                                     return;
-                            }
-                        }
-                        transaction.Commit();
-                    } catch (Exception exception) {
-                        await transaction.RollbackAsync();
-                        AnsiConsole.WriteException(exception);
+                                }
+
+                                if (configuration.BeVerbose)
+                                    AnsiConsole.MarkupLine($"[green]:check_mark: OK:[/] :file_folder: {safePeekedDir}");
+
+                                var entries = dirInfo.GetFileSystemEntries().OrderByDescending(e => e.Name);
+                                foreach (UnixFileSystemInfo entry in entries)
+                                {
+                                    string relativePath = Path.Combine(peekedDir, entry.Name);
+                                    string safeRelativePath = relativePath.Replace("[", "[[").Replace("]", "]]");
+
+                                    if (!entry.CanAccess(Mono.Unix.Native.AccessModes.R_OK))
+                                    {
+                                        if (entry.IsDirectory)
+                                            AnsiConsole.MarkupLine($"[red]:cross_mark: NO_ACCESS:[/] :file_folder: {safeRelativePath}");
+                                        else if (entry.IsRegularFile)
+                                            AnsiConsole.MarkupLine($"[red]:cross_mark: NO_ACCESS:[/] :page_facing_up: {safeRelativePath}");
+                                        continue;
+                                    }
+
+                                    if (entry.IsDirectory)
+                                    {
+                                        directoriesStack.Push(relativePath);
+                                        continue;
+                                    }
+
+                                    if (!entry.IsRegularFile)
+                                    {
+                                        AnsiConsole.MarkupLine($"[red]:cross_mark: NO_FILE:[/] :red_exclamation_mark: {safeRelativePath}");
+                                        continue;
+                                    }
+
+                                    await connection.ExecuteAsync("INSERT OR REPLACE INTO files (name, size, inode) VALUES (@name, @Length, @Inode);", new { name = relativePath, entry.Length, entry.Inode });
+
+                                    if (configuration.BeVerbose)
+                                        AnsiConsole.MarkupLine($"[green]:check_mark: OK:[/] :page_facing_up: {safeRelativePath}");
+
+                                    if (ct.IsCancellationRequested)
+                                        return;
+                                }
+                            }
+                            await transaction.CommitAsync(ct);
+                        }
+                        catch (Exception exception)
+                        {
+                            await transaction.RollbackAsync(ct);
+                            AnsiConsole.WriteException(exception);
+
+                            return;
+                        }
+
+                        if (configuration.BeVerbose) AnsiConsole.WriteLine();
 
-                        return;
                     }
 
                     ctx.Status("Finding duplicates...");
@@ -79,78 +108,474 @@ namespace Files {
 
                     var potential = connection.Query<(int cnt, long size)>("SELECT COUNT(*) cnt, size FROM files WHERE size != 0 GROUP BY size HAVING cnt > 1 ORDER BY size * cnt DESC;");
 
-                    foreach (var potentialFile in potential) {
-                        var sameSize = connection.Query<DbRecord>("SELECT name, size, inode FROM files WHERE size = @size",
+                    foreach (var potentialFile in potential)
+                    {
+                        if (ct.IsCancellationRequested)
+                            return;
+
+                        var sameSize = connection.Query<UnixFileRecord>("SELECT name, size, inode FROM files WHERE size = @size",
                             new { potentialFile.size }).ToList();
 
+                        sameSize.CalculateHashes();
+
+                        var recordsWithErrors = sameSize
+                            .Where(r => !r.Hash.HasValue);
+
+                        foreach (var dbRecord in recordsWithErrors)
+                        {
+                            AnsiConsole.MarkupLine($"[red]:cross_mark: NO_ACCESS:[/] :page_facing_up: {dbRecord.Name.Replace("[", "[[").Replace("]", "]]")}");
+                        }
+
                         var equalGrouped = sameSize
                             .Where(r => r.Hash.HasValue)
-                            .GroupBy(r=>r.Hash)
-                            .Where(g=>g.Count() > 1)
+                            .GroupBy(r => r.Hash)
+                            .Where(g => g.Count() > 1)
                             .ToList();
 
-                        foreach (var grp in equalGrouped) {
-                            var root = new Tree(":double_exclamation_mark: " + grp.Key);
-                            foreach (var item in grp) {
-                                root.AddNode(item.Name);
+                        foreach (var grp in equalGrouped)
+                        {
+                            if (ct.IsCancellationRequested)
+                                return;
+
+                            var records = grp.OrderByDescending(r => r.FileInfo.LinkCount).ToList();
+
+                            UnixFileRecord head = records.First();
+                            var tail = records.Skip(1).Where(r => r.INode != head.INode).ToList();
+                            var tailWithDuplicates = records.Skip(1).Where(r => r.INode == head.INode).ToList();
+
+                            ByteSize totalSize = records.Distinct(new DbRecordEqualityComparerByINode()).Sum(a => a.Size) - head.Size;
+
+                            var root = new Tree((head.Size + totalSize).ToStringWithDecimalPrefixedShortUnitName() + " total.");
+                            root.AddNode(((ByteSize)head.Size).ToStringWithDecimalPrefixedShortUnitName() + " " + head.Name.Replace("[", "[[").Replace("]", "]]"));
+                            foreach (var item in tail)
+                            {
+                                if (configuration.EnableLinking)
+                                {
+
+                                    try
+                                    {
+                                        // First rename
+                                        string tempFileName = item.FileInfo.FullName + ".to_hardlink";
+                                        File.Move(item.FileInfo.FullName, tempFileName);
+
+                                        try
+                                        {
+                                            // Then hardlink
+                                            head.FileInfo.CreateLink(item.FileInfo.FullName);
+
+                                            // Then delete
+                                            File.Delete(tempFileName);
+
+                                            root.AddNode("[green]:check_mark:[/] " +
+                                                         item.Name.Replace("[", "[[").Replace("]", "]]"));
+                                        }
+                                        catch (Exception)
+                                        {
+                                            File.Move(tempFileName, item.FileInfo.FullName);
+                                            throw;
+                                        }
+                                    }
+                                    catch (Exception exception)
+                                    {
+                                        AnsiConsole.WriteException(exception, ExceptionFormats.ShortenEverything);
+                                        root.AddNode("[red]:cross_mark:[/] " +
+                                                     item.Name.Replace("[", "[[").Replace("]", "]]"));
+                                    }
+                                }
+                                else
+                                {
+                                    root.AddNode(((ByteSize)item.Size).ToStringWithDecimalPrefixedShortUnitName() + " " + item.Name.Replace("[", "[[").Replace("]", "]]"));
+                                }
+                            }
+
+                            if (configuration.BeVerbose)
+                                foreach (var duplicate in tailWithDuplicates)
+                                {
+                                    root.AddNode("[white]:link:[/] 0B " +
+                                                 duplicate.Name.Replace("[", "[[").Replace("]", "]]"));
+                                }
+
+                            if (tail.Any() || configuration.BeVerbose)
+                            {
+                                AnsiConsole.Render(root);
+                                AnsiConsole.WriteLine();
                             }
-                            AnsiConsole.Render(root);
                         }
                     }
 
-        });
+                });
         }
 
-        private static async Task Main(string[] args) {
-            var verboseOption = new Option<bool>(new []{"--verbose", "-v"} ,"Verbose");
+        private static async Task InitializeDb(SqliteConnection connection)
+        {
+            await connection.ExecuteAsync(
+                "CREATE TABLE IF NOT EXISTS files (" +
+                        "name TEXT PRIMARY KEY, " +
+                        "size INTEGER NOT NULL, " +
+                        "inode INTEGER NOT NULL, " +
+                        "hash TEXT);");
+            await connection.ExecuteAsync("CREATE INDEX IF NOT EXISTS idx_files_size ON files(size);");
+            await connection.ExecuteAsync("CREATE INDEX IF NOT EXISTS idx_files_inode ON files(inode);");
+        }
+
+        private static async Task Main(string[] args)
+        {
+            var verboseOption = new Option<bool>(new[] { "--verbose", "-v" }, "Verbose");
+            var hardlinkOption = new Option<bool>(new[] { "--hardlink", "-l" }, "Hardlink duplicates");
+            var databaseOption = new Option<bool>(new[] { "--keep", "-k" }, () => true, "Keep database.");
+            var scanOption = new Option<bool>(new[] { "--no-scan" }, "Do not scan file system. Reuse database.");
+            var dbFileOption = new Option<FileInfo>(new[] { "--database", "-db" }, "Store database in file.");
             var directoryArgument = new Argument<DirectoryInfo>(
                 result => new DirectoryInfo("./"), isDefault: true)
-                {
+            {
                 Name = "directory",
                 Description = "Directory to scan.",
                 Arity = ArgumentArity.ZeroOrOne,
             }.ExistingOnly();
 
-            var rootCommand = new RootCommand("$ File -v false ./")
+            var rootCommand = new RootCommand("Find duplicate files.")
             {
                 verboseOption,
+                hardlinkOption,
+                databaseOption,
+                scanOption,
+                dbFileOption,
                 directoryArgument,
             };
 
             ParseResult result = rootCommand.Parse(args);
+
             ArgumentResult dirResult = result.FindResultFor(directoryArgument);
             var dir = new DirectoryInfo(
                 dirResult.Tokens.FirstOrDefault()?.Value
                 ?? dirResult.Argument.GetDefaultValue()?.ToString());
 
-            rootCommand.Handler = CommandHandler.Create<bool, CancellationToken>(
-                async (verbose, ct) => await IndexFiles(verbose, dir, ct));
+            var config = new Configuration
+            {
+                BeVerbose = result.ValueForOption(verboseOption),
+                EnableLinking = result.ValueForOption(hardlinkOption),
+                InitialDirectory = dir,
+                KeepDatabase = result.ValueForOption(databaseOption),
+                SkipFileScanning = result.ValueForOption(scanOption),
+                DatabaseFile = result.ValueForOption(dbFileOption),
+            };
+
+            rootCommand.Handler = CommandHandler.Create<CancellationToken>(
+                async ct =>
+                {
+                    //await IndexFiles(config, ct);
+                    await Begin(config, ct);
+                });
 
             await rootCommand.InvokeAsync(args);
         }
-    }
 
-    public class DbRecord {
-        private readonly Lazy<Guid?> _guid;
+        private static async Task Begin(Configuration configuration, CancellationToken ct) =>
+            await AnsiConsole.Status()
+                .StartAsync("Initializing...", async ctx =>
+                {
+                    string dbFileName = configuration.DatabaseFile?.FullName ?? ":memory:";
+                    await using var connection = new SqliteConnection($"Data Source={dbFileName};");
+                    connection.Open();
+                    await using var transaction = await connection.BeginTransactionAsync(ct);
 
-        public DbRecord() {
-            _guid = new Lazy<Guid?>(GetHash);
+                    try
+                    {
+                        await InitializeDb(connection);
+
+                        if (!configuration.SkipFileScanning)
+                        {
+                            await ScanFiles(configuration, connection, ctx, ct);
+                        }
+
+                        FindDuplicates(configuration, connection, ctx, ct);
+
+                        await transaction.CommitAsync(ct);
+                    }
+                    catch (OperationCanceledException)
+                    {
+                        await transaction.RollbackAsync();
+                        AnsiConsole.WriteLine("Canceled!");
+                    }
+                    catch (Exception exception)
+                    {
+                        await transaction.RollbackAsync();
+                        AnsiConsole.WriteException(exception);
+                    }
+                });
+
+        private static async Task ScanFiles(Configuration configuration, SqliteConnection sqliteConnection,
+            StatusContext statusContext, CancellationToken ct)
+        {
+            UnixFileSystemEnumerator.FilterEnumeratorDelegate filter = (directory, entry, entryType, errno) => true;
+
+            var pathEnumerable = UnixFileSystemEnumerator.EnumeratePaths(
+                configuration.InitialDirectory.ToString(),
+                filter,
+                ct);
+
+            foreach ((string entryPath, byte entryType, Errno errno) in pathEnumerable)
+            {
+                if (errno != 0)
+                {
+                    string errorDescription = UnixMarshal.GetErrorDescription(errno);
+                    string safeErrorDescription = errorDescription
+                        .Replace("[", "[[")
+                        .Replace("]", "]]");
+                    string safePath = entryPath
+                        .Replace("[", "[[")
+                        .Replace("]", "]]");
+                    AnsiConsole.MarkupLine($"[red]:cross_mark: {safeErrorDescription}:[/] :file_folder: {safePath}");
+
+                    continue;
+                }
+
+                string entryTypeEmoji = entryType switch
+                {
+                    DirentType.DT_DIR => Emoji.Known.FileFolder,
+                    DirentType.DT_REG => Emoji.Known.PageFacingUp,
+                    DirentType.DT_LNK => Emoji.Known.Link,
+                    DirentType.DT_BLK => Emoji.Known.ComputerDisk,
+                    DirentType.DT_CHR => Emoji.Known.Keyboard,
+                    DirentType.DT_FIFO => Emoji.Known.PButton,
+                    DirentType.DT_SOCK => Emoji.Known.ElectricPlug,
+                    DirentType.DT_UNKNOWN => Emoji.Known.Potato,
+                    _ => Emoji.Known.PileOfPoo,
+                };
+
+                if (!UnixFileSystemEnumerator.IsOfTarget(entryType, SearchTarget.DirectoriesAndFiles))
+                {
+                    if(!configuration.BeVerbose) continue;
+
+                    string safePath = entryPath
+                        .Replace("[", "[[")
+                        .Replace("]", "]]");
+
+                    string fileType = entryType switch
+                    {
+                        DirentType.DT_DIR => "Directory",
+                        DirentType.DT_REG => "Regular file",
+                        DirentType.DT_LNK => "Symbolic link",
+                        DirentType.DT_BLK => "Block device",
+                        DirentType.DT_CHR => "Character device",
+                        DirentType.DT_FIFO => "Named pipe",
+                        DirentType.DT_SOCK => "Socket",
+                        DirentType.DT_UNKNOWN => "UNKNOWN",
+                        _ => "WRONG",
+                    };
+
+                    AnsiConsole.MarkupLine($"[yellow]{Emoji.Known.FastForwardButton} {fileType}:[/] {entryTypeEmoji} {safePath}");
+
+                    continue;
+                }
+
+                UnixFileSystemInfo entry = entryType switch
+                {
+                    DirentType.DT_REG => new UnixFileInfo(entryPath),
+                    DirentType.DT_DIR => new UnixDirectoryInfo(entryPath),
+                    DirentType.DT_LNK => new UnixSymbolicLinkInfo(entryPath),
+                    _ => throw new FileLoadException($"Cannot scan {entryTypeEmoji} {entryPath}"),
+                };
+
+                if (!entry.GetValid())
+                {
+                    string errorDescription = UnixMarshal.GetErrorDescription(Stdlib.GetLastError());
+                    string safePath = entryPath
+                        .Replace("[", "[[")
+                        .Replace("]", "]]");
+                    AnsiConsole.MarkupLine($"[red]:cross_mark: {errorDescription}:[/] {entryTypeEmoji} {safePath}");
+                    continue;
+                }
+
+                string safeEntryPath = entryPath
+                    .Replace("[", "[[")
+                    .Replace("]", "]]");
+
+                if (entry.GetType() == typeof(UnixFileInfo)) // Faster than "is"
+                {
+                    var file = (UnixFileInfo) entry;
+                    var record = new UnixFileRecord(file);
+
+                    await sqliteConnection.ExecuteAsync("INSERT OR REPLACE INTO files (name, size, inode) VALUES (@Name, @Size, @INode);", record);
+
+                    if (configuration.BeVerbose)
+                        AnsiConsole.MarkupLine($"[green]:check_mark: OK:[/] {entryTypeEmoji} {safeEntryPath}");
+                }
+                else if (entry.GetType() == typeof(UnixDirectoryInfo)) // Faster than "is"
+                {
+                    var directory = (UnixDirectoryInfo)entry;
+                    statusContext.Status(safeEntryPath);
+                }
+                else if (entry.GetType() == typeof(UnixSymbolicLinkInfo)) // Faster than "is"
+                {
+                    var symLink = (UnixSymbolicLinkInfo)entry;
+                }
+
+                if (ct.IsCancellationRequested)
+                    return;
+            }
         }
 
-        public string Name { get; set; }
-        public long Size { get; set; }
-        public long Inode { get; set; }
-        public Guid? Hash => _guid.Value;
+        private static void FindDuplicates(Configuration configuration,
+            SqliteConnection connection, StatusContext ctx,
+            CancellationToken ct)
+        {
+            ctx.Status("Finding duplicates...");
+            ctx.Spinner(Spinner.Known.Aesthetic);
 
-        public Guid? GetHash() {
-            try {
-                using FileStream stream = File.OpenRead(Name);
-                var md5 = MD5.Create();
-                var bytes = md5.ComputeHash(stream);
-                return new Guid(bytes);
-            } catch {
-                return null;
+            var potential = connection.Query<(int cnt, long size)>(
+                "SELECT COUNT(*) cnt, size FROM files WHERE size != 0 GROUP BY size HAVING cnt > 1 ORDER BY size * cnt DESC;");
+
+            foreach (var potentialFile in potential)
+            {
+                ct.ThrowIfCancellationRequested();
+
+                var sameSize = connection.Query<UnixFileRecord>("SELECT name, size, inode FROM files WHERE size = @size",
+                    new { potentialFile.size }).ToList();
+
+                var recordsWithErrors = sameSize
+                    .Where(r => !r.Hash.HasValue);
+
+                foreach (var dbRecord in recordsWithErrors)
+                {
+                    AnsiConsole.MarkupLine(
+                        $"[red]:cross_mark: NO_ACCESS:[/] :page_facing_up: {dbRecord.Name.Replace("[", "[[").Replace("]", "]]")}");
+                }
+
+                var equalGrouped = sameSize
+                    .Where(r => r.Hash.HasValue)
+                    .GroupBy(r => r.Hash)
+                    .Where(g => g.Count() > 1)
+                    .ToList();
+
+                foreach (var grp in equalGrouped)
+                {
+                    ct.ThrowIfCancellationRequested();
+
+                    var records = grp.OrderByDescending(r => r.FileInfo.LinkCount).ToList();
+
+                    UnixFileRecord head = records.First();
+                    var tail = records.Skip(1).Where(r => r.INode != head.INode).ToList();
+                    var tailWithDuplicates = records.Skip(1).Where(r => r.INode == head.INode).ToList();
+
+                    ByteSize totalSize = records.Distinct(new DbRecordEqualityComparerByINode()).Sum(a => a.Size) - head.Size;
+
+                    var root = new Tree((head.Size + totalSize).ToStringWithDecimalPrefixedShortUnitName() + " total.");
+                    root.AddNode(((ByteSize)head.Size).ToStringWithDecimalPrefixedShortUnitName() + " " +
+                                 head.Name.Replace("[", "[[").Replace("]", "]]"));
+                    foreach (var item in tail)
+                    {
+                        if (configuration.EnableLinking)
+                        {
+                            try
+                            {
+                                // First rename
+                                string tempFileName = item.FileInfo.FullName + ".to_hardlink";
+                                File.Move(item.FileInfo.FullName, tempFileName);
+
+                                try
+                                {
+                                    // Then hardlink
+                                    head.FileInfo.CreateLink(item.FileInfo.FullName);
+
+                                    // Then delete
+                                    File.Delete(tempFileName);
+
+                                    root.AddNode("[green]:check_mark:[/] " +
+                                                 item.Name.Replace("[", "[[").Replace("]", "]]"));
+                                }
+                                catch (Exception)
+                                {
+                                    File.Move(tempFileName, item.FileInfo.FullName);
+                                    throw;
+                                }
+                            }
+                            catch (Exception exception)
+                            {
+                                AnsiConsole.WriteException(exception, ExceptionFormats.ShortenEverything);
+                                root.AddNode("[red]:cross_mark:[/] " +
+                                             item.Name.Replace("[", "[[").Replace("]", "]]"));
+                            }
+                        }
+                        else
+                        {
+                            root.AddNode(((ByteSize)item.Size).ToStringWithDecimalPrefixedShortUnitName() + " " +
+                                         item.Name.Replace("[", "[[").Replace("]", "]]"));
+                        }
+                    }
+
+                    if (configuration.BeVerbose)
+                        foreach (var duplicate in tailWithDuplicates)
+                        {
+                            root.AddNode("[white]:anchor:[/] 0B " +
+                                         duplicate.Name.Replace("[", "[[").Replace("]", "]]"));
+                        }
+
+                    if (tail.Any() || configuration.BeVerbose)
+                    {
+                        AnsiConsole.Render(root);
+                        AnsiConsole.WriteLine();
+                    }
+                }
             }
         }
     }
+
+    class Configuration
+    {
+        public bool BeVerbose { get; set; }
+        public bool EnableLinking { get; set; }
+        public DirectoryInfo InitialDirectory { get; set; }
+        public bool KeepDatabase { get; set; }
+        public bool SkipFileScanning { get; set; }
+        public FileInfo DatabaseFile { get; set; }
+    }
+
+    public class DbRecordEqualityComparerByINode : EqualityComparer<UnixFileRecord>
+    {
+        public override bool Equals(UnixFileRecord x, UnixFileRecord y)
+        {
+            return x?.INode == y?.INode;
+        }
+
+        public override int GetHashCode(UnixFileRecord obj)
+        {
+            return obj.INode.GetHashCode();
+        }
+    }
+
+    static class OriginalPathUnixFileSystemInfo
+    {
+        private static readonly Func<UnixFileSystemInfo, string> GetOriginalPathFunc;
+        private static readonly Func<UnixFileSystemInfo, bool> GetValidFunc;
+
+        static OriginalPathUnixFileSystemInfo()
+        {
+            var method = new DynamicMethod("cheat", typeof(string), new[] { typeof(UnixFileSystemInfo) }, typeof(UnixFileSystemInfo), true);
+            var il = method.GetILGenerator();
+            il.Emit(OpCodes.Ldarg_0);
+            //il.Emit(OpCodes.Castclass, typeof(UnixFileSystemInfo));
+            il.Emit(OpCodes.Callvirt, typeof(UnixFileSystemInfo)
+                .GetProperty("OriginalPath", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic)
+                .GetGetMethod(true));
+            il.Emit(OpCodes.Ret);
+            GetOriginalPathFunc = (Func<UnixFileSystemInfo, string>)method.CreateDelegate(typeof(Func<UnixFileSystemInfo, string>));
+
+
+            var method2 = new DynamicMethod("cheat2", typeof(bool), new[] { typeof(UnixFileSystemInfo) }, typeof(UnixFileSystemInfo), true);
+            var il2 = method2.GetILGenerator();
+            il2.Emit(OpCodes.Ldarg_0);
+            //il2.Emit(OpCodes.Castclass, typeof(UnixFileSystemInfo));
+            il2.Emit(OpCodes.Ldfld, typeof(UnixFileSystemInfo)
+                .GetField("valid", BindingFlags.Instance | BindingFlags.NonPublic));
+            il2.Emit(OpCodes.Ret);
+            GetValidFunc = (Func<UnixFileSystemInfo, bool>)method2.CreateDelegate(typeof(Func<UnixFileSystemInfo, bool>));
+        }
+
+        public static string GetOriginalPath(this UnixFileSystemInfo info) => GetOriginalPathFunc(info);
+
+        public static bool GetValid(this UnixFileSystemInfo info) => GetValidFunc(info);
+
+        public static long GetSizeOnDisk(this UnixFileSystemInfo info) => info.BlocksAllocated * 512;
+    }
 }

Files/Properties/launchSettings.json

@@ -2,6 +2,11 @@
   "profiles": {
     "Files": {
       "commandName": "Project"
+    },
+    "WSL 2": {
+      "commandName": "WSL2",
+      "environmentVariables": {},
+      "distributionName": ""
     }
   }
 }

Files/UnixFileRecord.cs

@@ -0,0 +1,224 @@
+using System;
+using System.Buffers;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Security.Cryptography;
+using System.Threading;
+using System.Threading.Tasks;
+using Mono.Unix;
+
+namespace Files
+{
+    public static class UnixFileRecordExtensions
+    {
+        public static void CalculateHashes(this IEnumerable<UnixFileRecord> records)
+        {
+            foreach (var recordsGroup in records.GroupBy(r => r.INode))
+            {
+                Guid? hash = UnixFileRecord.GetHash(recordsGroup.First().FileInfo);
+                if (!hash.HasValue) continue;
+
+                foreach (UnixFileRecord unixFileRecord in recordsGroup)
+                {
+                    unixFileRecord.SetHash(hash.Value);
+                }
+            }
+        }
+    }
+
+    public class UnixFileRecord
+    {
+        private readonly Lazy<Guid?> _guid;
+        private readonly Lazy<UnixFileInfo> _fileInfo;
+        private Guid? _preCalculatedHash = null;
+
+        public UnixFileRecord()
+        {
+            _guid = new Lazy<Guid?>(GetHash);
+            _fileInfo = new Lazy<UnixFileInfo>(GetFileInfo);
+        }
+
+        public UnixFileRecord(string filePath, long size, long iNode)
+        {
+            Name = filePath;
+            Size = size;
+            INode = iNode;
+            _guid = new Lazy<Guid?>(GetHash);
+            _fileInfo = new Lazy<UnixFileInfo>(GetFileInfo);
+        }
+
+        public UnixFileRecord(UnixFileInfo fileInfo)
+        {
+            _guid = new Lazy<Guid?>(GetHash);
+            _fileInfo = new Lazy<UnixFileInfo>(fileInfo);
+            Name = fileInfo.GetOriginalPath();
+            Size = fileInfo.Length;
+            INode = fileInfo.Inode;
+        }
+
+        public UnixFileRecord(UnixFileInfo fileInfo, Guid hash)
+        {
+            _guid = new Lazy<Guid?>(hash);
+            _fileInfo = new Lazy<UnixFileInfo>(fileInfo);
+            Name = fileInfo.GetOriginalPath();
+            Size = fileInfo.Length;
+            INode = fileInfo.Inode;
+        }
+
+        public string Name { get; init; }
+        public long Size { get; init; }
+        public long INode { get; init; }
+
+        public Guid? Hash => _guid.Value;
+        public UnixFileInfo FileInfo => _fileInfo.Value;
+
+        public void SetHash(Guid hash) => _preCalculatedHash = hash;
+
+        private UnixFileInfo GetFileInfo() => new(Name);
+
+        private Guid? GetHash() => _preCalculatedHash ??= GetHash(Name);
+
+        private async Task<Guid?> GetHashAsync(CancellationToken ct = default) => await GetHashAsync(Name, ct);
+
+        private Guid? GetHash2(CancellationToken ct = default) => GetHash2(Name, ct);
+
+        private async Task<Guid?> GetHash2Async(CancellationToken ct = default) => await GetHash2Async(Name, ct);
+
+        public static Guid? GetHash(string filePath)
+        {
+            try
+            {
+                using FileStream stream = File.OpenRead(filePath);
+                var md5 = MD5.Create();
+                var bytes = md5.ComputeHash(stream);
+                return new Guid(bytes);
+            }
+            catch
+            {
+                return null;
+            }
+        }
+
+        public static Guid? GetHash(UnixFileInfo file)
+        {
+            try
+            {
+                using UnixStream stream = file.Open(FileMode.Open);
+                var md5 = MD5.Create();
+                var bytes = md5.ComputeHash(stream);
+                return new Guid(bytes);
+            }
+            catch
+            {
+                return null;
+            }
+        }
+
+        public static async Task<Guid?> GetHashAsync(string filePath, CancellationToken ct = default)
+        {
+            try
+            {
+                await using FileStream stream = File.OpenRead(filePath);
+                var md5 = MD5.Create();
+                var bytes = await md5.ComputeHashAsync(stream, ct);
+                return new Guid(bytes);
+            }
+            catch
+            {
+                return null;
+            }
+        }
+
+        public static async Task<Guid?> GetHashAsync(UnixFileInfo file, CancellationToken ct = default)
+        {
+            try
+            {
+                await using UnixStream stream = file.Open(FileMode.Open);
+                var md5 = MD5.Create();
+                var bytes = await md5.ComputeHashAsync(stream, ct);
+                return new Guid(bytes);
+            }
+            catch
+            {
+                return null;
+            }
+        }
+
+        public static Guid? GetHash2(string filePath, CancellationToken ct = default)
+        {
+            using IncrementalHash incrementalHash = IncrementalHash.CreateHash(HashAlgorithmName.MD5);
+            using FileStream inputStream = File.OpenRead(filePath);
+
+            byte[] buffer = ArrayPool<byte>.Shared.Rent(4096);
+
+            try
+            {
+                int bytesRead;
+                int clearLimit = 0;
+
+                while ((bytesRead = inputStream.Read(buffer, 0, buffer.Length)) > 0)
+                {
+                    if (bytesRead > clearLimit)
+                    {
+                        clearLimit = bytesRead;
+                    }
+
+                    if (ct.IsCancellationRequested) return null;
+
+                    incrementalHash.AppendData(buffer, 0, bytesRead);
+                }
+
+                byte[] hashBytes = incrementalHash.GetHashAndReset();
+                return new Guid(hashBytes);
+            }
+            catch
+            {
+                return null;
+            }
+            finally
+            {
+                //CryptographicOperations.ZeroMemory(buffer.AsSpan(0, clearLimit));
+                ArrayPool<byte>.Shared.Return(buffer, clearArray: false);
+            }
+        }
+
+        public static async Task<Guid?> GetHash2Async(string filePath, CancellationToken ct = default)
+        {
+            using IncrementalHash incrementalHash = IncrementalHash.CreateHash(HashAlgorithmName.MD5);
+            await using FileStream inputStream = File.OpenRead(filePath);
+
+            byte[] buffer = ArrayPool<byte>.Shared.Rent(4096);
+
+            try
+            {
+                int bytesRead;
+                int clearLimit = 0;
+
+                while ((bytesRead = await inputStream.ReadAsync(buffer, 0, buffer.Length, ct)) > 0)
+                {
+                    if (bytesRead > clearLimit)
+                    {
+                        clearLimit = bytesRead;
+                    }
+
+                    if (ct.IsCancellationRequested) return null;
+
+                    incrementalHash.AppendData(buffer, 0, bytesRead);
+                }
+
+                byte[] hashBytes = incrementalHash.GetHashAndReset();
+                return new Guid(hashBytes);
+            }
+            catch
+            {
+                return null;
+            }
+            finally
+            {
+                //CryptographicOperations.ZeroMemory(buffer.AsSpan(0, clearLimit));
+                ArrayPool<byte>.Shared.Return(buffer, clearArray: false);
+            }
+        }
+    }
+}

Files/UnixFileSystemEnumerator.cs

@@ -0,0 +1,247 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using Mono.Unix;
+using Mono.Unix.Native;
+
+namespace Files
+{
+    [Flags]
+    public enum SearchTarget : byte
+    {
+        /// <summary>
+        /// Directories.
+        /// </summary>
+        Directories = 1,
+
+        /// <summary>
+        /// Regular files.
+        /// </summary>
+        Files = 2,
+
+        /// <summary>
+        /// Symbolic links.
+        /// </summary>
+        SymLinks = 4,
+
+        /// <summary>
+        /// Named pipes, or FIFOs.
+        /// </summary>
+        NamedPipes = 8,
+
+        /// <summary>
+        /// Local-domain socket.
+        /// </summary>
+        Sockets = 16,
+
+        /// <summary>
+        /// Character devices.
+        /// </summary>
+        CharacterDevices = 32,
+
+        /// <summary>
+        /// Block devices.
+        /// </summary>
+        BlockDevices = 64,
+
+        DirectoriesAndFiles = Directories | Files,
+        DirectoriesAndFilesAndSymLinks = Directories | Files | SymLinks,
+    }
+
+    /* File types for `d_type'.  */
+    public static class DirentType
+    {
+        /// <summary>
+        /// The type is unknown. Only some filesystems have full support to return the type of the file, others might always return this value.
+        /// </summary>
+        public const byte DT_UNKNOWN = 0;
+
+        /// <summary>
+        /// A named pipe, or FIFO.
+        /// </summary>
+        public const byte DT_FIFO = 1;
+
+        /// <summary>
+        /// A character device.
+        /// </summary>
+        public const byte DT_CHR = 2;
+
+        /// <summary>
+        /// A directory.
+        /// </summary>
+        public const byte DT_DIR = 4;
+
+        /// <summary>
+        /// A block device.
+        /// </summary>
+        public const byte DT_BLK = 6;
+
+        /// <summary>
+        /// A regular file.
+        /// </summary>
+        public const byte DT_REG = 8;
+
+        /// <summary>
+        /// A symbolic link.
+        /// </summary>
+        public const byte DT_LNK = 10;
+
+        /// <summary>
+        /// A local-domain socket.
+        /// </summary>
+        public const byte DT_SOCK = 12;
+    }
+
+    public static class UnixFileSystemEnumerator
+    {
+        private const string RelativeCurrentDir = ".";
+        private const string RelativeParentDir = "..";
+
+        public static bool TryGetEntries(string directoryPath, out List<Dirent> list, out Errno error)
+        {
+            list = new List<Dirent>();
+            IntPtr dirPointer = Syscall.opendir(directoryPath);
+            if (dirPointer == IntPtr.Zero)
+            {
+                error = Stdlib.GetLastError();
+                return false;
+            }
+
+            IntPtr result;
+            int returnValue;
+            do
+            {
+                Dirent entry = new();
+                returnValue = Syscall.readdir_r(dirPointer, entry, out result);
+
+                if (returnValue == 0 && result != IntPtr.Zero && (entry.d_name != RelativeCurrentDir && entry.d_name != RelativeParentDir))
+                {
+                    list.Add(entry);
+                }
+            }
+            while (returnValue == 0 && result != IntPtr.Zero);
+
+            if (returnValue == 0)
+            {
+                error = 0;
+                return true;
+            }
+
+            error = Stdlib.GetLastError();
+            return false;
+        }
+
+        public delegate bool FilterEnumeratorDelegate(string directory, string directoryEntry, byte entryType,
+            Errno errno);
+
+        public static IEnumerable<(string path, byte type, Errno errno)> EnumeratePaths(
+            string path, FilterEnumeratorDelegate filter = null, CancellationToken ct = default)
+        {
+            LinkedList<string> directoriesStack = new LinkedList<string>();
+            directoriesStack.AddLast(path);
+
+            while (directoriesStack.Last != null)
+            {
+                string dir = directoriesStack.Last.ValueRef;
+                directoriesStack.RemoveLast();
+
+                if (!TryGetEntries(dir, out List<Dirent> entries, out Errno errno))
+                {
+                    if(!(filter?.Invoke(dir, ".", DirentType.DT_DIR, errno) ?? true)) yield break;
+                    yield return (dir, DirentType.DT_DIR, errno);
+                }
+
+                foreach (Dirent entry in entries)
+                {
+                    ct.ThrowIfCancellationRequested();
+
+                    if (!(filter?.Invoke(dir, entry.d_name, entry.d_type, 0) ?? true)) continue;
+
+                    string combinedPath = Path.Combine(dir, entry.d_name);
+
+                    if (entry.d_type == DirentType.DT_DIR) // Directory
+                    {
+                        directoriesStack.AddLast(combinedPath);
+                    }
+
+                    yield return (combinedPath, entry.d_type, 0);
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool IsOfTarget(this Dirent entry, SearchTarget desiredTarget)
+        {
+            return entry.d_type switch
+            {
+                DirentType.DT_DIR => (desiredTarget & SearchTarget.Directories) == SearchTarget.Directories,
+                DirentType.DT_REG => (desiredTarget & SearchTarget.Files) == SearchTarget.Files,
+                DirentType.DT_LNK => (desiredTarget & SearchTarget.SymLinks) == SearchTarget.SymLinks,
+                DirentType.DT_FIFO => (desiredTarget & SearchTarget.NamedPipes) == SearchTarget.NamedPipes,
+                DirentType.DT_SOCK => (desiredTarget & SearchTarget.Sockets) == SearchTarget.Sockets,
+                DirentType.DT_CHR => (desiredTarget & SearchTarget.CharacterDevices) == SearchTarget.CharacterDevices,
+                DirentType.DT_BLK => (desiredTarget & SearchTarget.BlockDevices) == SearchTarget.BlockDevices,
+                _ => false
+            };
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool IsOfTarget(byte entryType, SearchTarget desiredTarget)
+        {
+            return entryType switch
+            {
+                DirentType.DT_DIR => (desiredTarget & SearchTarget.Directories) == SearchTarget.Directories,
+                DirentType.DT_REG => (desiredTarget & SearchTarget.Files) == SearchTarget.Files,
+                DirentType.DT_LNK => (desiredTarget & SearchTarget.SymLinks) == SearchTarget.SymLinks,
+                DirentType.DT_FIFO => (desiredTarget & SearchTarget.NamedPipes) == SearchTarget.NamedPipes,
+                DirentType.DT_SOCK => (desiredTarget & SearchTarget.Sockets) == SearchTarget.Sockets,
+                DirentType.DT_CHR => (desiredTarget & SearchTarget.CharacterDevices) == SearchTarget.CharacterDevices,
+                DirentType.DT_BLK => (desiredTarget & SearchTarget.BlockDevices) == SearchTarget.BlockDevices,
+                _ => false
+            };
+        }
+
+        public static Exception CreateExceptionForError(this Errno errno)
+        {
+            string errorDescription = UnixMarshal.GetErrorDescription(errno);
+            UnixIOException unixIoException = new(errno);
+            switch (errno)
+            {
+                case Errno.EPERM:
+                case Errno.EOPNOTSUPP:
+                    return new InvalidOperationException(errorDescription, unixIoException);
+                case Errno.ENOENT:
+                    return new FileNotFoundException(errorDescription, unixIoException);
+                case Errno.EIO:
+                case Errno.ENXIO:
+                case Errno.ENOSPC:
+                case Errno.ESPIPE:
+                case Errno.EROFS:
+                case Errno.ENOTEMPTY:
+                    return new IOException(errorDescription, unixIoException);
+                case Errno.ENOEXEC:
+                    return new InvalidProgramException(errorDescription, unixIoException);
+                case Errno.EBADF:
+                case Errno.EINVAL:
+                    return new ArgumentException(errorDescription, unixIoException);
+                case Errno.EACCES:
+                case Errno.EISDIR:
+                    return new UnauthorizedAccessException(errorDescription, unixIoException);
+                case Errno.EFAULT:
+                    return new NullReferenceException(errorDescription, unixIoException);
+                case Errno.ENOTDIR:
+                    return new DirectoryNotFoundException(errorDescription, unixIoException);
+                case Errno.ERANGE:
+                    return new ArgumentOutOfRangeException(errorDescription);
+                case Errno.ENAMETOOLONG:
+                    return new PathTooLongException(errorDescription, unixIoException);
+                case Errno.EOVERFLOW:
+                    return new OverflowException(errorDescription, unixIoException);
+                default:
+                    return unixIoException;
+            }
+        }
+    }
+}