import org.wasmer.Instance;
import org.wasmer.Memory;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.file.Files;
import java.nio.file.Paths;

class MemoryExample {
    public static void main(String[] args) throws IOException {
        // Read the WebAssembly bytes.
        byte[] bytes = Files.readAllBytes(Paths.get("memory.wasm"));

        // Instantiate the WebAssembly module.
        Instance instance = new Instance(bytes);

        // Get a pointer to the statically allocated string returned by `return_hello`.
        Integer pointer = (Integer) instance.exports.getFunction("return_hello").apply()[0];

        // Get the exported memory named `memory`.
        Memory memory = instance.exports.getMemory("memory");

        // Get a direct byte buffer view of the WebAssembly memory.
        ByteBuffer memoryBuffer = memory.buffer();

        // Prepare the byte array that will hold the data.
        byte[] data = new byte[13];

        // Let's position the cursor, and…
        memoryBuffer.position(pointer);
        
        // … read!
        memoryBuffer.get(data);

        // Let's encode back to a Java string.
        String result = new String(data);

        // Hello!
        assert result.equals("Hello, World!");

        instance.close();
    }
}