Native monitoring example

Author: manuelbl

examples/monitor_native/README.md

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+# Device Monitoring (Native)
+
+This example project demonstrates how to build a native application that
+monitors USB devices using [GraalVM](https://www.graalvm.org/) and
+this _Java Does USB_ library.
+
+## Build and Run
+
+### Prerequisites
+
+- [GraalVM](https://www.graalvm.org/) 25 or higher
+- [Maven](https://maven.apache.org/) 3.9 or higher
+
+
+### Preparation
+
+GraalVM needs help to learn about the Java FFM downcall and upcall descriptors,
+and it needs some help to include all required methods. The relevant items
+differ from operating system to operating system. When building the native image,
+the operating system must be selected by changing the path in the file
+`native-image.properties` in the directory
+`src/main/resources/META-INF/native-image/net.codecrete.usb.examples/monitor_native`.
+
+```properties
+Args = --enable-native-access=ALL-UNNAMED -H:ConfigurationFileDirectories=config/macos
+```
+
+Note the last word of the line. In this case, it is `macos`. Change this to
+`linux` or `windows` if needed.
+
+In your own Maven project, you might also need to move the file or rather rename
+directory. It must be named according to the pattern
+`src/main/resources/META-INF/native-image/<groupId>/<artifactId>`.
+
+Also check that the environment variable `JAVA_HOME` points to the GraalVM directory.
+
+
+### Building
+
+```shell
+mvn -Pnative package
+```
+
+
+### Running
+
+```shell
+./target/monitor-native
+```

examples/monitor_native/config/linux/reachability-metadata.json

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+{
+  "foreign": {
+    "downcalls": [
+      {
+        "returnType": "jint",
+        "parameterTypes": [
+          "void*",
+          "void*"
+        ]
+      },
+      {
+        "returnType": "jint",
+        "parameterTypes": [
+          "void*",
+          "void*",
+          "void*"
+        ]
+      },
+      {
+        "returnType": "jint",
+        "parameterTypes": [
+          "jint",
+          "jlong",
+          "void*"
+        ],
+        "options": {
+          "captureCallState": true,
+          "firstVariadicArg": 2
+        }
+      },
+      {
+        "returnType": "jint",
+        "parameterTypes": [
+          "jint"
+        ]
+      },
+      {
+        "returnType": "void*",
+        "parameterTypes": [
+          "void*"
+        ]
+      },
+      {
+        "returnType": "jint",
+        "parameterTypes": [
+          "jint",
+          "void*",
+          "jint",
+          "jint"
+        ],
+        "options": {
+          "captureCallState": true
+        }
+      },
+      {
+        "returnType": "void*",
+        "parameterTypes": []
+      },
+      {
+        "returnType": "jint",
+        "parameterTypes": [
+          "jint"
+        ],
+        "options": {
+          "captureCallState": true
+        }
+      },
+      {
+        "returnType": "jint",
+        "parameterTypes": [
+          "void*",
+          "jint"
+        ],
+        "options": {
+          "captureCallState": true
+        }
+      },
+      {
+        "returnType": "void*",
+        "parameterTypes": [
+          "void*",
+          "void*"
+        ]
+      },
+      {
+        "returnType": "void*",
+        "parameterTypes": [
+          "jint"
+        ]
+      },
+      {
+        "returnType": "jint",
+        "parameterTypes": [
+          "void*"
+        ]
+      },
+      {
+        "returnType": "jint",
+        "parameterTypes": [
+          "jint",
+          "jint",
+          "jint",
+          "void*"
+        ],
+        "options": {
+          "captureCallState": true
+        }
+      }
+    ]
+  }
+}