Truffle which is library for programming language implementations for GraalVM has NFI for native function call. However Polyglot applications cannot use it because it is internal language for Truffle.

nfiwrapper gives ability to use NFI from Polyglot applications. Thus you can call C functions directly without JNI.

Requirements

GraalVM 20.1.0 (JDK 11) or later

• You need to change some code and distribution.xml if you want to use it on GraalVM JDK 8.

How to build

$ export JAVA_HOME=$GRAALVM_HOME
$ mvn package

You can see the following files after building in target:

• truffle-nfi-wrapper.jar
  • nfiwrapper
• truffle-nfi-wrapper-<version>-component.jar
  • nfiwrapper component for gu

Install

Install truffle-nfi-wrapper-<version>-component.jar via gu.

You can see nfiwrapper on gu list if instlation is succeeded like following:

$ $GRAALVM_HOME/bin/gu list
ComponentId              Version             Component name      Origin
--------------------------------------------------------------------------------
js                       20.2.0              Graal.js
nfiwrapper               0.1.0               Truffle NFI Wrapper
graalvm                  20.2.0              GraalVM Core

Local install

$ $GRAALVM_HOME/bin/gu install -L target/truffle-nfi-wrapper-0.1.0-component.jar

Install from online catalog

You can install nfiwrapper via content catalog on this repository. This catalog contains information for GraalVM 20.1.0 and 20.2.0.

$ gu install -C https://raw.githubusercontent.com/YaSuenag/nfiwrapper/master/nfiwrapper-catalog-java11.properties nfiwrapper

Try nfiwrapper

nfiwrapper passes all of commands to NFI, so you can refer document of Truffle NFI for use.

1. Load library ( load or default )
2. Get member from function symbol
3. Bind signature
4. Invoke

You can refer document of Truffle NFI to know signature format and/or type mapping between C and Truffle NFI.

For example, examples/GetPID.java would get PID via getpid() (on Linux) or GetCurrentProcessId() (on Windows).

$ $GRAALVM_HOME/bin/javac GetPID.java
$ $GRAALVM_HOME/bin/java GetPID
PID: 980

Also you can use nfiwrapper on polyglot command. Following code is example on polyglot on Linux.

$ $GRAALVM_HOME/bin/polyglot --shell
GraalVM MultiLanguage Shell 20.2.0
Copyright (c) 2013-2019, Oracle and/or its affiliates
  JavaScript version 20.2.0
  TruffleNFIWrapper version 0.1.0
Usage:
  Use Ctrl+L to switch language and Ctrl+D to exit.
  Enter -usage to get a list of available commands.
js> library = Polyglot.eval('nfiwrapper', 'load "libc.so.6"')
{}
js> getpid = library['getpid'].bind('():SINT32')
Native Symbol
js> getpid()
806

Crash example

MemSetCrash.java is crash example at memset() with writing NULL. It is useful to check coredump and/or hs_err log. This example is for Linux only.