Introduce GlobalSettings.NativeLibraryPath

Allow consumers to set the native library path in case they are
running in a strange environment that they have little control
over where the actual executing assembly lives (but do have some
control over the references) and want to point the library to the
native location explicitly.

Author: Edward Thomson

LibGit2Sharp.Tests/GlobalSettingsFixture.cs

@@ -55,5 +55,14 @@ public void CanRetrieveValidVersionString()
                 Assert.True(matchGroups[i].Success);
             }
         }
+
+        [Fact]
+        public void TryingToResetNativeLibraryPathAfterLoadedThrows()
+        {
+            // Do something that loads the native library
+            Assert.NotNull(GlobalSettings.Version.Features);
+
+            Assert.Throws<LibGit2SharpException>(() => { GlobalSettings.NativeLibraryPath = "C:/Foo"; });
+        }
     }
 }

LibGit2Sharp/Core/NativeMethods.cs

@@ -64,44 +64,19 @@ internal static void RemoveHandle()
 
         static NativeMethods()
         {
-            if (!IsRunningOnUnix())
+            if (Platform.OperatingSystem == OperatingSystemType.Windows)
             {
-                string originalAssemblypath = new Uri(Assembly.GetExecutingAssembly().EscapedCodeBase).LocalPath;
-
-                string currentArchSubPath = "NativeBinaries/" + ProcessorArchitecture;
-
-                string path = Path.Combine(Path.GetDirectoryName(originalAssemblypath), currentArchSubPath);
+                string path = Path.Combine(GlobalSettings.NativeLibraryPath, Platform.ProcessorArchitecture);
 
                 const string pathEnvVariable = "PATH";
                 Environment.SetEnvironmentVariable(pathEnvVariable,
-                                                   String.Format(CultureInfo.InvariantCulture, "{0}{1}{2}", path, Path.PathSeparator, Environment.GetEnvironmentVariable(pathEnvVariable)));
+                    String.Format(CultureInfo.InvariantCulture, "{0}{1}{2}", path, Path.PathSeparator, Environment.GetEnvironmentVariable(pathEnvVariable)));
             }
 
             // See LibraryLifetimeObject description.
             lifetimeObject = new LibraryLifetimeObject();
         }
 
-        public static string ProcessorArchitecture
-        {
-            get
-            {
-                if (Environment.Is64BitProcess)
-                {
-                    return "amd64";
-                }
-
-                return "x86";
-            }
-        }
-
-        // Should match LibGit2Sharp.Tests.TestHelpers.BaseFixture.IsRunningOnUnix()
-        private static bool IsRunningOnUnix()
-        {
-            // see http://mono-project.com/FAQ%3a_Technical#Mono_Platforms
-            var p = (int)Environment.OSVersion.Platform;
-            return (p == 4) || (p == 6) || (p == 128);
-        }
-
         [DllImport(libgit2)]
         internal static extern GitErrorSafeHandle giterr_last();
 

LibGit2Sharp/Core/Platform.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace LibGit2Sharp.Core
+{
+    internal enum OperatingSystemType
+    {
+        Windows,
+        Unix,
+        MacOSX
+    }
+
+    internal class Platform
+    {
+        public static string ProcessorArchitecture
+        {
+            get
+            {
+                if (Environment.Is64BitProcess)
+                {
+                    return "amd64";
+                }
+
+                return "x86";
+            }
+        }
+
+        public static OperatingSystemType OperatingSystem
+        {
+            get
+            {
+                // See http://www.mono-project.com/docs/faq/technical/#how-to-detect-the-execution-platform
+                var platformId = (int)Environment.OSVersion.Platform;
+
+                switch ((int)Environment.OSVersion.Platform)
+                {
+                    case 4:
+                    case 128:
+                        return OperatingSystemType.Unix;
+                    case 6:
+                        return OperatingSystemType.MacOSX;
+                    default:
+                        return OperatingSystemType.Windows;
+                }
+            }
+        }
+    }
+}

LibGit2Sharp/GlobalSettings.cs

@@ -1,4 +1,6 @@
 using System;
+using System.IO;
+using System.Reflection;
 using LibGit2Sharp.Core;
 
 namespace LibGit2Sharp
@@ -12,6 +14,17 @@ public static class GlobalSettings
 
         private static LogConfiguration logConfiguration = LogConfiguration.None;
 
+        private static string nativeLibraryPath;
+
+        static GlobalSettings()
+        {
+            if (Platform.OperatingSystem == OperatingSystemType.Windows)
+            {
+                string managedPath = new Uri(Assembly.GetExecutingAssembly().EscapedCodeBase).LocalPath;
+                nativeLibraryPath = Path.Combine(Path.GetDirectoryName(managedPath), "NativeBinaries");
+            }
+        }
+
         /// <summary>
         /// Returns information related to the current LibGit2Sharp
         /// library.
@@ -108,5 +121,41 @@ public static LogConfiguration LogConfiguration
                 return logConfiguration;
             }
         }
+
+        /// <summary>
+        /// Sets a hint path for searching for native binaries: when
+        /// specified, native binaries will first be searched in a
+        /// subdirectory of the given path corresponding to the architecture
+        /// (eg, "x86" or "amd64") before falling back to the default
+        /// path ("NativeBinaries\x86" or "NativeBinaries\amd64" next
+        /// to the application).
+        /// <para>
+        /// This must be set before any other calls to the library,
+        /// and is not available on Unix platforms: see your dynamic
+        /// library loader's documentation for details.
+        /// </para>
+        /// </summary>
+        public static string NativeLibraryPath
+        {
+            get
+            {
+                if (Platform.OperatingSystem != OperatingSystemType.Windows)
+                {
+                    throw new LibGit2SharpException("Querying the native hint path is only supported on Windows platforms");
+                }
+
+                return nativeLibraryPath;
+            }
+
+            set
+            {
+                if (Platform.OperatingSystem != OperatingSystemType.Windows)
+                {
+                    throw new LibGit2SharpException("Setting the native hint path is only supported on Windows platforms");
+                }
+
+                nativeLibraryPath = value;
+            }
+        }
     }
 }

LibGit2Sharp/LibGit2Sharp.csproj

@@ -68,6 +68,7 @@
     <Compile Include="CommitOptions.cs" />
     <Compile Include="CommitSortStrategies.cs" />
     <Compile Include="CompareOptions.cs" />
+    <Compile Include="Core\Platform.cs" />
     <Compile Include="DescribeOptions.cs" />
     <Compile Include="DescribeStrategy.cs" />
     <Compile Include="Core\GitDescribeFormatOptions.cs" />

LibGit2Sharp/Version.cs

@@ -98,7 +98,7 @@ private string RetrieveVersion()
                 InformationalVersion,
                 LibGit2SharpCommitSha,
                 LibGit2CommitSha,
-                NativeMethods.ProcessorArchitecture,
+                Platform.ProcessorArchitecture,
                 features);
         }