Add support for a single shared libvips binary on Windows (#211)

When targeting .NET 6.0 or higher.
kleisauke · Oct 14, 2024 · 1448040 · 1448040
1 parent 2f4f658
commit 1448040
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -4,6 +4,9 @@ All notable changes to NetVips will be documented in this file. See [here](CHANG
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/) and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [3.0.0] - TBD
+### Added
+- Add support for a single shared libvips binary on Windows ([#211](https://github.com/kleisauke/net-vips/issues/211)).
+
 ### Removed
 - Drop support for .NET Standard 2.0 and Mono. NetVips now targets .NET 6 (`net6.0`) and .NET Framework 4.5.2 (`net452`) moving forward.
   See https://devblogs.microsoft.com/dotnet/the-future-of-net-standard/ for more information.

diff --git a/build/Build.cs b/build/Build.cs
@@ -132,21 +132,10 @@ protected override void OnBuildInitialized()
         .DependsOn(Clean)
         .Executes(() =>
         {
-            // Need to build the macOS and *nix DLL first.
-            DotNetBuild(c => c
-                .SetProjectFile(Solution.NetVips)
-                .SetConfiguration(Configuration)
-                .SetFramework("netstandard2.0")
-                .AddProperty("Platform", "AnyCPU")
-                .CombineWith(
-                    new[] { "OSX", "Unix" },
-                    (_, os) => _.AddProperty("TargetOS", os)));
-
             DotNetPack(c => c
                 .SetProject(Solution.NetVips)
                 .SetConfiguration(Configuration)
                 .SetOutputDirectory(ArtifactsDirectory)
-                .AddProperty("TargetOS", "Windows")
             );
         });
 

diff --git a/src/NetVips/Interop/Libraries.OSX.cs b/src/NetVips/Interop/Libraries.OSX.cs
diff --git a/src/NetVips/Interop/Libraries.Unix.cs b/src/NetVips/Interop/Libraries.Unix.cs
diff --git a/src/NetVips/Interop/Libraries.Windows.cs b/src/NetVips/Interop/Libraries.Windows.cs
diff --git a/src/NetVips/Interop/Libraries.cs b/src/NetVips/Interop/Libraries.cs
@@ -0,0 +1,13 @@
+namespace NetVips.Interop
+{
+    internal static class Libraries
+    {
+        /// <remarks>
+        /// These library names are remapped in a cross-platform manner,
+        /// <see cref="ModuleInitializer.Initialize"/>.
+        /// </remarks>
+        internal const string GLib = "libglib-2.0-0.dll",
+                              GObject = "libgobject-2.0-0.dll",
+                              Vips = "libvips-42.dll";
+    }
+}
diff --git a/src/NetVips/ModuleInitializer.cs b/src/NetVips/ModuleInitializer.cs
@@ -1,6 +1,10 @@
 namespace NetVips
 {
     using System;
+    using System.Reflection;
+    using System.Collections.Generic;
+    using System.Runtime.InteropServices;
+    using Interop;
 
     /// <summary>
     /// All code inside the <see cref="Initialize"/> method is ran as soon as the assembly is loaded.
@@ -22,6 +26,63 @@ public static class ModuleInitializer
         /// </summary>
         public static int? Version;
 
+#if NET6_0_OR_GREATER
+        /// <summary>
+        /// Windows specific: is GLib statically-linked in `libvips-42.dll`?
+        /// </summary>
+        [System.Runtime.Versioning.SupportedOSPlatform("windows")]
+        private static bool _gLibStaticallyLinked = true;
+
+        /// <summary>
+        /// A cache for <see cref="DllImportResolver"/>.
+        /// </summary>
+        internal static readonly Dictionary<string, IntPtr> DllImportCache =
+            new Dictionary<string, IntPtr>();
+
+        internal static string RemapLibraryName(string libraryName)
+        {
+            // For Windows, we try to locate the GLib symbols within
+            // `libvips-42.dll` first. If these symbols cannot be found there,
+            // we proceed to locate them within `libglib-2.0-0.dll` and
+            // `libgobject-2.0-0.dll`. Note that distributing a single shared
+            // library is only possible when we drop support for .NET Framework.
+            // Therefore, we always ship at least 3 DLLs for now.
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                return _gLibStaticallyLinked ? Libraries.Vips : libraryName;
+            }
+
+            // We can safely remap the library names to `libvips.so.42` on *nix
+            // and `libvips.42.dylib` on macOS since DLLImport uses dlsym() there.
+            // This function also searches for named symbols in the dependencies
+            // of the shared library. Therefore, we can provide libvips as a
+            // single shared library with all dependencies statically linked
+            // without breaking compatibility with the shared builds
+            // (i.e. what is usually installed via package managers).
+            return RuntimeInformation.IsOSPlatform(OSPlatform.OSX)
+                ? "libvips.42.dylib"
+                : "libvips.so.42";
+        }
+
+        internal static IntPtr DllImportResolver(string libraryName, Assembly assembly, DllImportSearchPath? searchPath)
+        {
+            libraryName = RemapLibraryName(libraryName);
+            if (DllImportCache.TryGetValue(libraryName, out var cachedHandle))
+            {
+                return cachedHandle;
+            }
+
+            if (NativeLibrary.TryLoad(libraryName, assembly, searchPath, out var handle))
+            {
+                DllImportCache[libraryName] = handle;
+                return handle;
+            }
+
+            // Fallback to the default import resolver.
+            return IntPtr.Zero;
+        }
+#endif
+
         /// <summary>
         /// Initializes the module.
         /// </summary>
@@ -30,6 +91,10 @@ public static class ModuleInitializer
 #pragma warning restore CA2255
         public static void Initialize()
         {
+#if NET6_0_OR_GREATER
+            NativeLibrary.SetDllImportResolver(typeof(ModuleInitializer).Assembly, DllImportResolver);
+#endif
+
             try
             {
                 VipsInitialized = NetVips.Init();
@@ -38,6 +103,19 @@ public static void Initialize()
                     Version = NetVips.Version(0, false);
                     Version = (Version << 8) + NetVips.Version(1, false);
                     Version = (Version << 8) + NetVips.Version(2, false);
+
+#if NET6_0_OR_GREATER
+                    if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) return;
+
+                    try
+                    {
+                        _gLibStaticallyLinked = NetVips.TypeFromName("VipsImage") != IntPtr.Zero;
+                    }
+                    catch
+                    {
+                        _gLibStaticallyLinked = false;
+                    }
+#endif
                 }
                 else
                 {

diff --git a/src/NetVips/NetVips.csproj b/src/NetVips/NetVips.csproj
@@ -11,30 +11,12 @@
     <StartupObject />
     <Platforms>x64;x86;ARM64;ARM32</Platforms>
     <Optimize>true</Optimize>
-    <DefaultItemExcludes>$(DefaultItemExcludes);Interop\Libraries.*.cs</DefaultItemExcludes>
     <AppendRuntimeIdentifierToOutputPath>false</AppendRuntimeIdentifierToOutputPath>
-    <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
     <IsTrimmable Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net6.0'))">true</IsTrimmable>
     <IsAotCompatible Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net8.0'))">true</IsAotCompatible>
   </PropertyGroup>
 
-  <!-- Give an initial value based on the operating system where it's currently running on. -->
-  <PropertyGroup Condition="'$(TargetOS)' == ''">
-    <TargetOS Condition="$([MSBuild]::IsOSPlatform('Linux')) OR $([MSBuild]::IsOSPlatform('FreeBSD'))">Unix</TargetOS>
-    <TargetOS Condition="$([MSBuild]::IsOSPlatform('OSX'))">OSX</TargetOS>
-    <TargetOS Condition="$([MSBuild]::IsOSPlatform('Windows'))">Windows</TargetOS>
-  </PropertyGroup>
-
-  <!-- Append target operating system to output path -->
-  <PropertyGroup>
-    <OutputPath>$(MSBuildThisFileDirectory)bin\$(Platform)\$(Configuration)\$(TargetFramework)\$(TargetOS)</OutputPath>
-    <IntermediateOutputPath>$(BaseIntermediateOutputPath)\$(Platform)\$(Configuration)\$(TargetFramework)\$(TargetOS)\</IntermediateOutputPath>
-  </PropertyGroup>
-
   <ItemGroup>
-    <Compile Include="Interop\Libraries.$(TargetOS).cs">
-        <Link>Interop\Libraries.cs</Link>
-    </Compile>
     <InternalsVisibleTo Include="$(AssemblyName).Tests" />
     <InternalsVisibleTo Include="$(AssemblyName).Samples" />
   </ItemGroup>
@@ -43,16 +25,4 @@
     <PackageReference Include="System.Buffers" Version="4.5.1" />
   </ItemGroup>
 
-  <!-- Include .NET Standard packages on *nix and macOS -->
-  <ItemGroup>
-    <None Include="$(MSBuildThisFileDirectory)bin\$(Platform)\$(Configuration)\netstandard2.0\Unix\$(AssemblyName).dll">
-      <Pack>true</Pack>
-      <PackagePath>runtimes\unix\lib\netstandard2.0</PackagePath>
-    </None>
-    <None Include="$(MSBuildThisFileDirectory)bin\$(Platform)\$(Configuration)\netstandard2.0\OSX\$(AssemblyName).dll">
-      <Pack>true</Pack>
-      <PackagePath>runtimes\osx\lib\netstandard2.0</PackagePath>
-    </None>
-  </ItemGroup>
-
 </Project>