Add overload method to load natives from JAR using a ClassLoader

As it will try to find the resource in the corresponding module and not the class's module only

FFM needs it as it fetches natives from another module, this is necessary for users using modules

Author: freya022

api/src/main/java/dev/freya02/discord/zstd/api/DiscordZstdNativesLoader.java

@@ -77,4 +77,34 @@ public static synchronized boolean loadFromJar(String resourcePath, Class<?> cla
         load(nativePath);
         return true;
     }
+
+    /**
+     * Loads the natives using the provided path from the provided class.
+     *
+     * <p>When, and only when using modules, the resource will be loaded from one of the modules loaded by the provided class loader.
+     * <br>If the resource path does not represent a valid package name, it can be loaded from any module, if it forms a valid package name,
+     * it is subject to encapsulation rules specified by {@link java.lang.Module#getResourceAsStream(String) Module.getResourceAsStream}.
+     *
+     * @param  resourcePath
+     *         The path to the native library in the provided class
+     * @param  loader
+     *         The class loader from which to load the resource from
+     *
+     * @throws IllegalArgumentException
+     *         If {@code resourcePath} or {@code loader} is {@code null}
+     * @throws IOException
+     *         If the resource does not exist or when extracting it fails
+     *
+     * @return {@code true} if the natives were loaded, {@code false} if they already were
+     */
+    public static synchronized boolean loadFromJar(String resourcePath, ClassLoader loader) throws IOException {
+        if (init)
+            return false;
+        Checks.notNull(resourcePath, "Resource path");
+        Checks.notNull(loader, "Class loader");
+
+        Path nativePath = IOUtil.copyNativeFromJar(resourcePath, loader);
+        load(nativePath);
+        return true;
+    }
 }

api/src/main/java/dev/freya02/discord/zstd/api/IOUtil.java

@@ -13,8 +13,27 @@ static Path copyNativeFromJar(String resourcePath, Class<?> clazz) throws IOExce
         path.toFile().deleteOnExit();
 
         try (InputStream stream = clazz.getResourceAsStream(resourcePath)) {
+            if (stream == null) {
+                if (resourcePath.startsWith("/")) {
+                    throw new FileNotFoundException("Natives not found at '" + resourcePath + "'");
+                } else {
+                    throw new FileNotFoundException("Natives not found at '" + resourcePath + "' relative to '" + clazz.getPackage().getName() + "'");
+                }
+            }
+
+            Files.copy(stream, path, StandardCopyOption.REPLACE_EXISTING);
+        }
+
+        return path;
+    }
+
+    static Path copyNativeFromJar(String resourcePath, ClassLoader loader) throws IOException {
+        final Path path = Files.createTempFile("libzstd", null);
+        path.toFile().deleteOnExit();
+
+        try (InputStream stream = loader.getResourceAsStream(resourcePath)) {
             if (stream == null)
-                throw new FileNotFoundException("Natives not found at '" + resourcePath + "' relative to '" + clazz.getPackage().getName() + "'");
+                throw new FileNotFoundException("Natives not found at '" + resourcePath + "'");
 
             Files.copy(stream, path, StandardCopyOption.REPLACE_EXISTING);
         }

ffm-impl/src/main/java/dev/freya02/discord/zstd/ffm/DiscordZstdFFM.java

@@ -18,8 +18,9 @@ public DiscordZstdFFM() throws IOException {
         // Load natives if they weren't already
         if (!DiscordZstdNativesLoader.isLoaded()) {
             NativeUtil.System system = NativeUtil.getSystem();
-            String absoluteNativeResource = String.format("/dev/freya02/discord/zstd/natives/%s/libzstd.%s", system.platform, system.sharedLibraryExtension);
-            DiscordZstdNativesLoader.loadFromJar(absoluteNativeResource, DiscordZstd.class);
+            String absoluteNativeResource = String.format("dev/freya02/discord/zstd/natives/%s/libzstd.%s", system.platform, system.sharedLibraryExtension);
+            // Use ClassLoader as natives are in another module
+            DiscordZstdNativesLoader.loadFromJar(absoluteNativeResource, DiscordZstd.class.getClassLoader());
         }
     }