fastFFI: Modern and Efficient FFI for Java and C++

Basically, fastFFI has three components:

• FFI: DSL and API used to develop FFI applications.
• Annotation Processor: the code generator for FFI.
• LLVM4JNI: LLVM4JNI has two submodules:
  • LLVM4JNI: a tool that translates LLVM bitcode into Java bytecode.
  • LLVM4JNI Runtime: the runtime component used by generated bytecode.

An FFI application must include ffi and llvm4jni-runtime in its class path as runtime dependency.

Build

1. Checkout source code

   git clone <path-to-fastffi> fastffi

2. Prepare building environment

   export LLVM11_HOME=<path-to-llvm-11>

   LLVM11_HOME should point to the home of LLVM 11. In Ubuntu, it is at /usr/lib/llvm-11. Basically, the build procedure the following binary:

   • $LLVM11_HOME/bin/clang++
   • $LLVM11_HOME/bin/ld.lld
   • $LLVM11_HOME/lib/cmake/llvm

3. Use fastFFI with Maven.

   <properties>
       <fastffi.revision>0.1.2</fastffi.revision>
   </properties>
   
   <dependencies>
       <!-- The FFI annotation -->
       <dependency>
           <groupId>com.alibaba.fastffi</groupId>
           <artifactId>ffi</artifactId>
           <version>${fastffi.revision}</version>
       </dependency>
       <!-- The FFI annotation processor for code generation -->
       <dependency>
           <groupId>com.alibaba.fastffi</groupId>
           <artifactId>annotation-processor</artifactId>
           <version>${fastffi.revision}</version>
       </dependency>
   
       <!-- The runtime component of LLVM4JNI -->
       <dependency>
           <groupId>com.alibaba.fastffi</groupId>
           <artifactId>llvm4jni</artifactId>
           <version>${fastffi.revision}</version>
           <classifier>${os.detected.classifier}</classifier>
       </dependency>
       <dependency>
           <groupId>com.alibaba.fastffi</groupId>
           <artifactId>llvm4jni-runtime</artifactId>
           <version>${fastffi.revision}</version>
       </dependency>
   </dependencies>
   
   <plugins>
       <plugin>
           <groupId>kr.motd.maven</groupId>
           <artifactId>os-maven-plugin</artifactId>
           <version>1.7.0</version>
           <executions>
               <execution>
                   <phase>initialize</phase>
                   <goals>
                       <goal>detect</goal>
                   </goals>
               </execution>
           </executions>
       </plugin>
   </plugins>

4. Use maven to build your applications.

   The generated code, including Java and C++ code, is available in <project.dir>/target/generated-source/annotations

Options

A Java programming language compiler must support standard options in the format -Akey[=value]. fastFFI provides the following options:

1. fastffi.handleException: whether generating code to handle C++ exceptions
   • default value: false
2. fastffi.manualBoxing: using new Integer() or new Long() to box a primitive integer.
   • default value: true
   • Auto boxing uses Integer.valueOf or Long.valueOf, which cannot be properly handled by the escape analysis of C2 compiler.
3. fastffi.strictTypeCheck
   • default value: false
4. fastffi.nullReturnValueCheck
   • default value: true
   • insert additional null check for native pointers
5. fastffi.cxxOutputLocation
   • default value: CLASS_OUTPUT
   • accept values: CLASS_OUTPUT, SOURCE_OUTPUT, NATIVE_HEADER_OUTPUT.
6. fastffi.traceJNICalls
   • default value: false
   • generate stuffs to trace the invocations of JNI wrappers
7. fastffi.compactFFINames
   • default value: true
   • generate compact FFI wrapper type names, non-compact names will benefit debugging, but increase the binary size

Usage:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.8.0</version>
    <configuration>
        <compilerVersion>${javac.target}</compilerVersion>
        <source>${javac.target}</source>
        <target>${javac.target}</target>
        <compilerArgs>
            <arg>-Afastffi.strictTypeCheck=true</arg>
        </compilerArgs>
    </configuration>
</plugin>

Build Mac OS

0. Install a JDK (JDK 8 and 11)

1. Install LLVM 11, Maven and CMake

   brew install llvm@11 cmake maven

2. Set ENV

   export LLVM11_HOME=/usr/local/opt/llvm@11

FAQ

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