Fix/url encoded mutex (#2709)

* Replace Mutex name hashing with URI escaping

* Make SharedMutexNameStrategy configurable to switch back to legacy if needed

* Adjust member visibility

* Re-introduce normalization in sha1 hash

* Falling back to sha1 if uri encode is not safe

* Refactor SharedMutexNameFactory to remove NETSTANDARD2_0 preprocessor directives and simplify OS detection

---------

Co-authored-by: Joyless <[email protected]>

Author: JKamsker

LiteDB/Client/Shared/SharedEngine.cs

@@ -3,6 +3,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Threading;
+using LiteDB.Client.Shared;
 using LiteDB.Vector;
 
 namespace LiteDB
@@ -18,7 +19,7 @@ public SharedEngine(EngineSettings settings)
         {
             _settings = settings;
 
-            var name = Path.GetFullPath(settings.Filename).ToLower().Sha1();
+            var name = SharedMutexNameFactory.Create(settings.Filename, settings.SharedMutexNameStrategy);
 
             try
             {

LiteDB/Client/Shared/SharedMutexNameFactory.cs

@@ -0,0 +1,92 @@
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Security.Cryptography;
+using System.Text;
+using LiteDB.Engine;
+
+namespace LiteDB.Client.Shared;
+
+internal static class SharedMutexNameFactory
+{
+    // Effective Windows limit for named mutexes (conservative).
+    private const int WINDOWS_MUTEX_NAME_MAX = 250;
+
+    // If the caller adds "Global\" (7 chars) + the name + ".Mutex" (7 chars) to the mutex name,
+    // we account for it conservatively here without baking it into the return value.
+    // Adjust if your caller prepends something longer.
+    private const int CONSERVATIVE_EXTERNAL_PREFIX_LENGTH = 13; // e.g., "Global\\" + name + ".Mutex"
+
+    internal static string Create(string fileName, SharedMutexNameStrategy strategy)
+    {
+        return strategy switch
+        {
+            SharedMutexNameStrategy.Default => CreateUsingUriEncodingWithFallback(fileName),
+            SharedMutexNameStrategy.UriEscape => CreateUsingUriEncoding(fileName),
+            SharedMutexNameStrategy.Sha1Hash => CreateUsingSha1(fileName),
+            _ => throw new ArgumentOutOfRangeException(nameof(strategy), strategy, null)
+        };
+    }
+
+    private static string CreateUsingUriEncodingWithFallback(string fileName)
+    {
+        var normalized = Normalize(fileName);
+        var uri = Uri.EscapeDataString(normalized);
+
+        if (IsWindows() &&
+            uri.Length + CONSERVATIVE_EXTERNAL_PREFIX_LENGTH > WINDOWS_MUTEX_NAME_MAX)
+        {
+            // Short, stable fallback well under the limit.
+            return "sha1-" + ComputeSha1Hex(normalized);
+        }
+
+        return uri;
+    }
+
+    private static string CreateUsingUriEncoding(string fileName)
+    {
+        var normalized = Normalize(fileName);
+        var uri = Uri.EscapeDataString(normalized);
+
+        if (IsWindows() &&
+            uri.Length + CONSERVATIVE_EXTERNAL_PREFIX_LENGTH > WINDOWS_MUTEX_NAME_MAX)
+        {
+            // Fallback to SHA to avoid ArgumentException on Windows.
+            return "sha1-" + ComputeSha1Hex(normalized);
+        }
+
+        return uri;
+    }
+
+    private static bool IsWindows()
+    {
+        return RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
+    }
+
+    internal static string CreateUsingSha1(string value)
+    {
+        var normalized = Normalize(value);
+        return ComputeSha1Hex(normalized);
+    }
+
+    private static string Normalize(string path)
+    {
+        // Invariant casing + absolute path yields stable identity.
+        return Path.GetFullPath(path).ToLowerInvariant();
+    }
+
+    private static string ComputeSha1Hex(string input)
+    {
+        var data = Encoding.UTF8.GetBytes(input);
+        using var sha = SHA1.Create();
+        var hashData = sha.ComputeHash(data);
+
+        var sb = new StringBuilder(hashData.Length * 2);
+        foreach (var b in hashData)
+        {
+            sb.Append(b.ToString("X2"));
+        }
+
+        return sb.ToString();
+    }
+}

LiteDB/Engine/EngineSettings.cs

@@ -71,6 +71,11 @@ public class EngineSettings
         /// Is used to transform a <see cref="BsonValue"/> from the database on read. This can be used to upgrade data from older versions.
         /// </summary>
         public Func<string, BsonValue, BsonValue> ReadTransform { get; set; }
+        
+        /// <summary>
+        /// Determines how the mutex name is generated.
+        /// </summary>
+        public SharedMutexNameStrategy SharedMutexNameStrategy { get; set; }
 
         /// <summary>
         /// Create new IStreamFactory for datafile

LiteDB/Engine/SharedMutexNameStrategy.cs

@@ -0,0 +1,9 @@
+
+namespace LiteDB.Engine;
+
+public enum SharedMutexNameStrategy
+{
+    Default,
+    UriEscape,
+    Sha1Hash
+}

LiteDB/Utils/Extensions/StringExtensions.cs

@@ -37,24 +37,6 @@ public static bool IsWord(this string str)
             return true;
         }
 
-        public static string Sha1(this string value)
-        {
-            var data = Encoding.UTF8.GetBytes(value);
-
-            using (var sha = SHA1.Create())
-            {
-                var hashData = sha.ComputeHash(data);
-                var hash = new StringBuilder();
-
-                foreach (var b in hashData)
-                {
-                    hash.Append(b.ToString("X2"));
-                }
-
-                return hash.ToString();
-            }
-        }
-
         /// <summary>
         /// Implement SqlLike in C# string - based on
         /// https://stackoverflow.com/a/8583383/3286260