Jeannie: Granting Java Native Interface

Developers Their Wishes

Martin Hirzel, Robert Grimm

Presented by: Mengtao Sun SoS Lab, Lehigh University

Motivation

FFI: Foreign Function Interface

OS Services

Legacy code

Performance

Convenience

Design Goals

Productivity: writing & maintaining code

Safety: preventing & detecting bugs

Efficiency

Portability: Different OS & VM

Jeannie

A new FFI for Java

Combining Java and C into one language

Jeannie compiler

Producing conventional JNI code

High-quality error messages

JNI Example

Jeannie Example

Support full

C syntax

Native methods have a body

Nested

block Nested

expression

Can nest to

any depth

Jeannie Build Process

Socket.jni

Socket.jni.i

Preprocessor

Jeannie Compiler

Socket.i Socket.java

Java Compiler

Java sources

Network.jar

C Compiler

C sources

Network.dll

Translation Scheme

“1”

“2”

class JavaEnv {

int x

int z

native m1()

m2(CEnv)

native m3(CEnv)

m4(CEnv)

}

struct CEnv {

jint y

};

Java_C_m1(JEnv)

Java_C_m3(JEnv,CEnv)

Jeannie source code Generated code

1

2

4 3

Typing

Type equivalences

Primitive types: char ≡ jchar

Reference types: java.lang.Object ≡ jobject

Nested expressions have the same types

Java references are opaque in C

java.io.IOException ≡ `java.io.IOException

C pointers/structs/unions are illegal in Java

Java Garbage Collection

Jeannie recommends that programmers do

not store Java references in C’s static

variables or heap-allocated data structures.

JNI Jeannie

Local

referenc

e

Implicit

(do not collect until

control returns to Java)

Global

referenc

e

Do not collect

until user calls

DeleteGlobalR

ef

Not supported

(just store in

Java and use

`x.f)

Compiler Stages Jeannie code

Jeannie AST

Jeannie AST+SymTab

C code Java code

Jeannie Parser

Jeannie Analyzer

Code generator

Jeannie grammar

Syntactic Analysis Jeannie code

Jeannie AST

Jeannie AST+SymTab

C code Java code

Jeannie Parser

Jeannie Analyzer

Code generator

Jeannie grammar

C grammar

Java grammar

Rats!

parser

generator

Semantic Analysis Jeannie code

Jeannie AST

Jeannie AST+SymTab

C code Java code

Jeannie Parser

Jeannie Analyzer

Code generator

Jeannie grammar

C grammar

Java grammar

Rats!

parser

generator

xtc visitors

Common type representation

Code Generation Jeannie code

Jeannie AST

Jeannie AST+SymTab

Jeannie Parser

Jeannie Analyzer

Code generator

Jeannie grammar

C grammar

Java grammar

Rats!

parser

generator

xtc visitors

Common type representation

C AST Java AST

C code Java code

C pretty printer Java pretty printer

xtc

AST generator

Evaluation

Portability

“Portability is a strong point of JNI, and the

Jeannie compiler preserves it.”

Productivity

Jeannie is more concise than JNI

Jeannie keeps the maintenance cost low

Evaluation (cont.)

Efficiency

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

JavaBDD: 11-Queens

JavaBDD: Rubik's Cube

Empty C block in Java

Empty Java block in C

Constant C expr. in Java

Constant Java expr. in C

Exception in C in Java

With array read

With array writeJ9 / Linux

HotSpot / OS X

Array Access

Nested expression is simple:

for (i = 0, n = `ja.length; i < n; i++)

s += `ja[`i];

• But bulk access is faster:

with (jint* ca = `ja) {

jint n = `ja.length;

for (jint i=0; i<n; i++)

s += ca[i];

}

Array Access (cont.)

Bulk vs. Simple array access

0 10 20 30 40 50 60 70 80 90

Write

Read

J9 / Linux

HotSpot / OS X

Conclusion

Jeannie: a new language integrating Java

with C

Portability

Productivity

Efficiency

Language composition

Rats!

xtc

Critique

Sooooooooo long!!!

The idea of language composition is

fabulous. However:

Debugging (Jinn)

Fault-isolation (Robusta)

Thanks!

Presented by: Mengtao Sun SoS Lab, Lehigh University