Adds support for a custom SymbolProvider in NativeLibrary

src/com/sun/jna/Library.java

@@ -114,6 +114,11 @@ public interface Library {
      */
     String OPTION_CLASSLOADER = "classloader";
 
+    /**
+     * Supports a custom symbol provider for the NativeLibrary (see {@link SymbolProvider})
+     */
+    String OPTION_SYMBOL_PROVIDER = "symbol-provider";
+
     static class Handler implements InvocationHandler {
 
         static final Method OBJECT_TOSTRING;

src/com/sun/jna/NativeLibrary.java

@@ -96,6 +96,8 @@ public class NativeLibrary implements Closeable {
     private final Map<String, Function> functions = new HashMap<String, Function>();
     final int callFlags;
     private String encoding;
+    private SymbolProvider symbolProvider;
+    private SymbolProvider defaultSymbolProvider;
     final Map<String, ?> options;
 
     private static final Map<String, Reference<NativeLibrary>> libraries = new HashMap<String, Reference<NativeLibrary>>();
@@ -123,6 +125,17 @@ private NativeLibrary(String libraryName, String libraryPath, long handle, Map<S
         this.callFlags = callingConvention;
         this.options = options;
         this.encoding = (String)options.get(Library.OPTION_STRING_ENCODING);
+        this.symbolProvider = (SymbolProvider)options.get(Library.OPTION_SYMBOL_PROVIDER);
+        if (this.symbolProvider != null) {
+            //noinspection Convert2Lambda
+            defaultSymbolProvider = new SymbolProvider() {
+                @Override
+                public long getSymbolAddress(long handle, String name, SymbolProvider parent) {
+                    return Native.findSymbol(handle, name);
+                }
+            };
+        }
+
         if (this.encoding == null) {
             this.encoding = Native.getDefaultStringEncoding();
         }
@@ -636,7 +649,11 @@ long getSymbolAddress(String name) {
         if (handle == 0) {
             throw new UnsatisfiedLinkError("Library has been unloaded");
         }
-        return Native.findSymbol(handle, name);
+        if (symbolProvider != null) {
+            return symbolProvider.getSymbolAddress(handle, name, defaultSymbolProvider);
+        } else {
+            return Native.findSymbol(handle, name);
+        }
     }
 
     @Override

src/com/sun/jna/SymbolProvider.java

@@ -0,0 +1,43 @@
+/* Copyright (c) 2022 Carlos Ballesteros, All Rights Reserved
+ *
+ * The contents of this file is dual-licensed under 2
+ * alternative Open Source/Free licenses: LGPL 2.1 or later and
+ * Apache License 2.0. (starting with JNA version 4.0.0).
+ *
+ * You can freely decide which license you want to apply to
+ * the project.
+ *
+ * You may obtain a copy of the LGPL License at:
+ *
+ * http://www.gnu.org/licenses/licenses.html
+ *
+ * A copy is also included in the downloadable source code package
+ * containing JNA, in file "LGPL2.1".
+ *
+ * You may obtain a copy of the Apache License at:
+ *
+ * http://www.apache.org/licenses/
+ *
+ * A copy is also included in the downloadable source code package
+ * containing JNA, in file "AL2.0".
+ */
+package com.sun.jna;
+
+/**
+ * Interface to define a custom symbol provider.
+ *
+ * This can be used for method hooking, or special
+ * classes like direct mapping the Win32 OpenGL.
+ */
+public interface SymbolProvider {
+    /**
+     * Gets the address of a symbol by its name and the handle of the library.
+     *
+     * @param handle Handle of the original library
+     * @param name Name of the symbol to load
+     * @param parent Parent symbol provider
+     *
+     * @return Address of the symbol, typically a function.
+     */
+    long getSymbolAddress(long handle, String name, SymbolProvider parent);
+}

test/com/sun/jna/DirectTest.java

@@ -44,13 +44,36 @@ public static void main(java.lang.String[] argList) {
 
     static class MathLibrary {
 
+        public static native double sin(double x);
         public static native double cos(double x);
 
         static {
             Native.register(Platform.MATH_LIBRARY_NAME);
         }
     }
 
+    static class MathLibraryWithSymbolProvider {
+
+        public static native double sin(double x);
+        public static native double cos(double x);
+
+        static {
+            Native.register(MathLibraryWithSymbolProvider.class, NativeLibrary.getInstance(Platform.MATH_LIBRARY_NAME, Collections.singletonMap(
+                    Library.OPTION_SYMBOL_PROVIDER,
+                    new SymbolProvider() {
+                        @Override
+                        public long getSymbolAddress(long handle, String name, SymbolProvider parent) {
+                            if (name.equals("sin")) {
+                                return parent.getSymbolAddress(handle, "cos", null);
+                            } else {
+                                return parent.getSymbolAddress(handle, "sin", null);
+                            }
+                        }
+                    }
+            )));
+        }
+    }
+
     interface MathInterface extends Library {
         double cos(double x);
     }
@@ -299,6 +322,11 @@ public String getFunctionName(NativeLibrary lib, Method method) {
         }
     }
 
+    public void testDirectMappingSymbolProvider() {
+        assertEquals(MathLibrary.cos(0.0), MathLibraryWithSymbolProvider.sin(0.0));
+        assertEquals(MathLibrary.sin(0.0), MathLibraryWithSymbolProvider.cos(0.0));
+    }
+
     public static class PointerNativeMapped implements NativeMapped {
         String nativeMethodName;
         @Override