vendoring NetVips

vendor/NetVips/ModuleInitializer.cs

@@ -0,0 +1,139 @@
+using System;
+using System.Collections.Generic;
+using System.Reflection;
+using System.Runtime.InteropServices;
+using NetVips.Interop;
+
+namespace NetVips;
+
+/// <summary>
+/// All code inside the <see cref="Initialize"/> method is ran as soon as the assembly is loaded.
+/// </summary>
+public static class ModuleInitializer
+{
+    /// <summary>
+    /// Is vips initialized?
+    /// </summary>
+    public static bool VipsInitialized;
+
+    /// <summary>
+    /// Contains the exception when initialization of libvips fails.
+    /// </summary>
+    public static Exception Exception;
+
+    /// <summary>
+    /// Could contain the version number of libvips in an 3-bytes integer.
+    /// </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, nint> DllImportCache = new();
+
+    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 this is only possible when
+        // targeting .NET 6 or higher. As a result, we always ship at least
+        // 3 DLLs in a separate package for .NET Framework.
+        if (OperatingSystem.IsWindows())
+        {
+            return _gLibStaticallyLinked ? Libraries.Vips : libraryName;
+        }
+
+        // FIXME: Switch to `OperatingSystem.IsApplePlatform()` once public.
+        // See: https://github.com/dotnet/runtime/issues/113262
+        var isApplePlatform = OperatingSystem.IsMacOS() || OperatingSystem.IsIOS() ||
+                              OperatingSystem.IsTvOS() || OperatingSystem.IsWatchOS();
+
+        // 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 isApplePlatform ? "libvips.42.dylib" : "libvips.so.42";
+    }
+
+    internal static nint DllImportResolver(string libraryName, Assembly assembly, DllImportSearchPath? searchPath)
+    {
+        libraryName = RemapLibraryName(libraryName);
+        if (DllImportCache.TryGetValue(libraryName, out var cachedHandle))
+        {
+            return cachedHandle;
+        }
+
+        var handle = NativeLibrary.Load(libraryName, assembly, searchPath);
+        DllImportCache[libraryName] = handle;
+
+        return handle;
+    }
+#endif
+
+    /// <summary>
+    /// Initializes the module.
+    /// </summary>
+#pragma warning disable CA2255
+    [System.Runtime.CompilerServices.ModuleInitializer]
+#pragma warning restore CA2255
+    public static void Initialize()
+    {
+#if NET6_0_OR_GREATER
+        try
+        {
+            NativeLibrary.SetDllImportResolver(typeof(ModuleInitializer).Assembly, DllImportResolver);
+        }
+        catch
+        {
+            // Ignored; allows this function to be called multiple times.
+        }
+#endif
+
+        try
+        {
+            VipsInitialized = NetVips.Init();
+            if (VipsInitialized)
+            {
+                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 (!OperatingSystem.IsWindows())
+                {
+                    return;
+                }
+
+                try
+                {
+                    _gLibStaticallyLinked = NetVips.TypeFromName("VipsImage") != IntPtr.Zero;
+                }
+                catch
+                {
+                    _gLibStaticallyLinked = false;
+                }
+#endif
+            }
+            else
+            {
+                Exception = new VipsException("unable to initialize libvips");
+            }
+        }
+        catch (Exception e)
+        {
+            VipsInitialized = false;
+            Exception = e;
+        }
+    }
+}