Panama4Newbies_Atlanta.pdf

JAVA 19
PROJECT PANAMA
 
4
 
NEWBIES
A friendly intro to JEP 419’s Foreign
Function & Memory API

About Me
• A Sr. Developer Advocate at Azul Systems

• Developing software for 20+ years

• Authored & Tech Reviewed Java books

• A JavaFX (fanboy) enthusiast

• Loves sharing and advocating Java based technologies
 
 
Other interests:
 
Graphics, UI, Game programming, GEO spatial data & map
visualizations, Custom UI controls, IoT, Smart phones, AI, and
Robotics and Boating.

 
Twitter: @carldea
 
LinkedIn: https://github.com/carldea
 
Email: cdea@azul.com
Carl Dea

Panama4Newbies
https://github.com/carldea/panama4newbies
https://foojay.io/today/project-panama-for-newbies-part-1
 

 

OpenGL & SDL RFID Card Reader
JNI
Java interop?

JNI Pain Points
Java Native Interface

The JACOB Project: A JAva-COM Bridge
Now you can call COM Automation from any Win32 Java VM using JNI
Copyright 1999-2004 Dan Adler
Latest Version: October 17, 2004 (V1.8)
https://danadler.com/tech-articles/jacob-2/

jacob.jar
jacob.dll
Win32 DLL
myApplication.jar
Java  
Application

jacob.jar
jacob.dll
Win32 DLL
myApplication.jar
Java Library

jacob.jar
jacob.dll
Win32 DLL
myApplication.jar
Native  
Wrapper lib

jacob.jar
jacob.dll
Win32 DLL
myApplication.jar
OS Native  
Library

Wormholes are hypothetical bridges through space-time (Image credit: Getty)
Future

JEP 389: 1st Incubator
Foreign-Memory Access API
Vector API
JEP 338: 1st Incubator JEP 383: 2nd Incubator
JEP 393: 3rd Incubator
Foreign Linker API
Foreign Function
 
&
 
Memory Access API
Project Panama
JEP 419: 2nd Incubator
JEP 424: Preview

jdk.incubator.foreign
JEP 424 Preview
java.lang.foreign
+ 
Bug-fixes

Bene
fi
ts
Ease of use — Replace the Java Native Interface (JNI) with a superior, pure-Java
development model.
Performance — Provide performance that is comparable to, if not better than,
existing APIs such as JNI and sun.misc.Unsafe.
General Purpose — Provide ways to operate on different kinds of foreign memory
(e.g., native memory, persistent memory, and managed heap memory) and, over time, to
accommodate other platforms (e.g., 32-bit x86) and foreign functions written in languages
other than C (e.g., C++, Fortran).
Safety — Disable unsafe operations by default, allowing them only after
explicit opt-in from application developers or end users.

Ease of use — Replace the Java Native Interface (JNI) with a superior, pure-Java
development model.
Performance — Provide performance that is comparable to, if not better than,
existing APIs such as JNI and sun.misc.Unsafe.
General Purpose — Provide ways to operate on different kinds of foreign memory
(e.g., native memory, persistent memory, and managed heap memory) and, over time, to
accommodate other platforms (e.g., 32-bit x86) and foreign functions written in languages
other than C (e.g., C++, Fortran).
Safety — Disable unsafe operations by default, allowing them only after
explicit opt-in from application developers or end users.
Bene
fi
ts

ABI
Application
 
Binary
 
InterFace

OpenGL & SDL
Displaying 3D surfaces

RFID Card Reading
Reading keychain tags

Apple’s Text to Speech
Wanna sound like a robot?

FFMpeg
 
w/ JavaFX Apps
Overlay graphics on top of video

Where to get Panama?
--add-modules jdk.incubator.foreign

Early Access Builds
https://jdk.java.net/panama
Feedback
panama-dev@openjdk.java.net
Contribute or Build OpenJDK
yourself
https://github.com/openjdk/panama-foreign

JAVA_HOME
c:> set JAVA_HOME=<unzipped_dir>jdk-19.jdkContentsHome

c:> set PATH=%JAVA_HOME%bin;%PATH%

MacOS/Linux

$ export JAVA_HOME=<untarred_dir>/jdk-19.jdk/Contents/Home

$ export PATH=$JAVA_HOME/bin:$PATH

PATH
Setting Environment Variables
Windows

java -version
Quick Check
openjdk version “19-internal" 2022-09-20

OpenJDK Runtime Environment (build 19-internal+0-
adhoc.jdoe.panama-foreign)

OpenJDK 64-Bit Server VM (build 19-internal+0-
adhoc.jdoe.panama-foreign, mixed mode, sharing)
JDK 19 Panama

MethodHandle(s)
Understanding Low level Panama code such as MethodHandles
since JDK 7

What’s a MethodHandle?
A method handle is a Java object that references a
native C function or C variable in memory and
the ability to accessed or invoked from Java code.
 
 
In the C/C++ world symbols are a unique lookup of C
functions and variables from the C linker
(java.library.path).
In layman’s (newbie) terms:

What’s a MethodHandle?
A method handle is a typed, directly executable
reference to an underlying method, constructor,
fi
eld, or
similar low-level operation, with optional
transformations of arguments or return values.These
transformations are quite general, and include such
patterns as conversion, insertion, deletion, and
substitution.
According to the Javadoc Documentation since JDK 7

Unix/Linux functions
Getting the process ID using the getpid() function
Really a C int

Creating a MethodHandle - JDK 18+
MethodHandle class
FunctionDescriptor
 
describes return type from C
NativeSymbol
 
C symbols from library path
Note: For better performance make method handles
fi
nal static

Is there a better way?
FILE *freopen(const char *filename, const char *mode, FILE *stream)

jextract
Output: Calling getpid() (1234)
https://github.com/openjdk/jextract

C Standard Input/Output
 
Header

int printf(const char *format, ...)

Zero means OK.
 
Anything else is an
error or status code

in Java
Panama
Using
 
Jextract

jextract -h
Quick Check
Option Description

------ -----------

-?, -h, --help print help

-C <String> pass through argument for clang

-I <String> specify include files path

-d <String> specify where to place generated files

--dump-includes <String> dump included symbols into specified file

--header-class-name <String> name of the header class

--include-function <String> name of function to include

--include-macro <String> name of constant macro to include

--include-struct <String> name of struct definition to include

--include-typedef <String> name of type definition to include

--include-union <String> name of union definition to include

--include-var <String> name of global variable to include

-l <String> specify a library

--source generate java sources

-t, --target-package <String> target package for specified header files

Panama’s JExtract

jextract -h
Quick Check
Option Description

------ -----------
















Panama’s JExtract

C headers path
 
ie: /usr/local/include

jextract -h
Quick Check
Option Description

------ -----------
















Panama’s JExtract

Generated Code
 
ie: ./classes
 
./generated/src

jextract -h
Quick Check
Option Description

------ -----------
















Panama’s JExtract

Library
 
ie: tensorflow

jextract -h
Quick Check
Option Description

------ -----------
















Panama’s JExtract

Generated Java Source
 
ie: org/unix/foo_h.java

jextract -h
Quick Check
Option Description

------ -----------
















Panama’s JExtract

Package namespace prefix
 
ie: org.unix

$ export C_INCLUDE=/usr/local/include
 
# or depending where the defaults are installed

$ export C_INCLUDE=/usr/include
MacOS

$ export C_INCLUDE=Applications/Xcode.app/Contents/
Developer/Platforms/MacOSX.platform/Developer/SDKs/
MacOSX.sdk/usr/include
Let’s jextract stdio.h
Windows

Tech Note: UsingVSCode 2022 - https://docs.microsoft.com/en-us/cpp/build/
walkthrough-compile-a-c-program-on-the-command-line?
view=msvc-170#open-a-developer-command-prompt-in-visual-studio-2022
Linux
Create a convenient
environment variable
C_INCLUDE

$ jextract -d classes
 
-t org.unix
 
-I $C_INCLUDE
 
$C_INCLUDE/stdio.h

Generate Java Classes

 
-t org.unix
 
-I $C_INCLUDE
 
$C_INCLUDE/stdio.h

Destination Directory ./classes

 
-t org.unix
 
-I $C_INCLUDE
 
$C_INCLUDE/stdio.h

Package Namespace: org.unix

 
-t org.unix
 
-I $C_INCLUDE
 
$C_INCLUDE/stdio.h

Header include directory

 
-t org.unix
 
-I $C_INCLUDE
 
$C_INCLUDE/stdio.h

Target Header
fi
le

Generated Java Classes

$ jextract --source
 
-d generated/src
 
-t org.unix
 
-I $C_INCLUDE

$C_INCLUDE/stdio.h

Generate Java Sources

$ jextract --source
 
-d generated/src
 
-t org.unix
 
-I $C_INCLUDE

$C_INCLUDE/stdio.h

Generate Java Source Code
Generate Source Directory

Generated Java Sources

--add-modules jdk.incubator.foreign

IntelliJ - Preferences
IDE Setup

HelloWorld.java
JDK 18+ ResourceScope
Implements Closable.
Cleans up after try block.

allocateUtf8String()
HelloWorld.java

JDK 18+
C Functions

MemorySegment
 
to
 
Java String
C String converts to Java String object

Let’s Run HelloWorld.java
Enabling Native Access

Adding foreign function & memory module

Java Application

ValueLayout
To create a C primitive use CLinker’s C ValueLayouts such as
 
C_INT
 
C_DOUBLE
 
C_POINTER, etc.
MemorySegment

ValueLayout
 
C_INT
 
C_DOUBLE
 
C_POINTER, etc. Native Allocator

ValueLayout
 
C_INT
 
C_DOUBLE
 
C_POINTER, etc.

ValueLayout
 
C_INT
 
C_DOUBLE
 
C_POINTER, etc.
JDK 18+ uses the
 
MemorySegment class’
 
get()/set() methods

C Primitive Arrays
SegmentAllocator.allocateArray()

Primitive Array - JDK 18+
To create a C primitive Arrays use:
SegmentAllocator.implicitAllocator().allocateArray()
00 00 00 00 00 00 00 01
0
00 00 00 00 00 00 00 02
1

Summary
•The 3Ws of Project Panama
•MethodHandle class
•jextract
•MethodSegment class
•ValueLayout class
•allocateArray() method

But there’s more…
C Structs
C Pointers
C Callbacks
Other Languages
 
(Polyglot)

Q/A
Thank you for coming!
Twitter: @carldea
 
Blog: carlfx.com & foojay.io
 
Github: https://github.com/carldea

Email: cdea@azul.com
 
LinkedIn: https://www.linkedin.com/in/carldea

References
Links, Mailing Lists, videos, blogs
• Panama 4 Newbies – https://foojay.io/today/project-panama-for-newbies-part-1

• Panama EA builds - https://jdk.java.net/panama

• Feedback - panama-dev@openjdk.java.net

• Mailing List - https://mail.openjdk.java.net/mailman/listinfo/panama-dev

• JEP 412 1st incubator - https://openjdk.java.net/jeps/412

• JEP 419 2nd incubator - https://openjdk.java.net/jeps/419

• JEP 424 Preview - https://openjdk.java.net/jeps/424

• Foojay.io – https://foojay.io

• Panama Samples - https://github.com/sundararajana/panama-jextract-samples

• Panama at GitHub – https://github.com/openjdk/panama-foreign

• Panama Update by Maurizio Cimadamore - https://www.youtube.com/watch?v=r4dNRVWYaZI

• Upcalls by M.C. - https://cr.openjdk.java.net/~mcimadamore/panama/f
fi
.html

• Going Meta to Valhalla & Panama w/ John Rose - https://www.youtube.com/watch?v=49GUljUmGHg

• Rust & Panama - https://jornvernee.github.io/rust/panama-f
fi
/2021/09/03/rust-panama-helloworld.html

• Method Handles - https://download.java.net/java/early_access/panama/docs/api/java.base/java/lang/
invoke/MethodHandle.html

• Jextract on GitHub - https://github.com/openjdk/jextract

What’s a C Pointer?
C supports the use of pointers, a type of reference that records the
address or location of an object or function in memory. Pointers can
be dereferenced to access data stored at the address pointed to, or
to invoke a pointed-to function. Pointers can be manipulated using
assignment or pointer arithmetic.
The C Programming Language book
 
by
 
Brian W. Kernighan & Dennis M. Ritchie

ptr = &x x = 5
0x0DDBA11 0xCAFEBABE 0xCAFEBABE 5
Address or Location

ptr = &x x = 5
0x0DDBA11 0xCAFEBABE 0xCAFEBABE 5
Storage

Obtaining a C Pointer in Panama
The reference or address of a C int variable:

How to Dereference A Pointer?
Obtain value at the address referenced by the pointer.

Dereferencing a C Pointer in Panama - JDK 18+
MemoryAddress class

What’s a C Struct?
To put it simply, this is the ancestor to C++ & Java's
concept of classes or records.
Declaring pt of type Point struct

How to Create a Struct in
Panama?
Use GroupLayout and MemoryLayout to describe a C struct.

Creating C Structs in Panama
Using MemoryLayout’s structLayout() method.

Accessing C Structs in Panama - JDK 18+
To access a MemoryLayout (C Struct) use VarHandles.

Present Day
JNI
JNI Requires Native Wrapper Code

Rock, Paper Scissors
Playing against the computer you lose every time

Native Access to
 
Mic & Sound Audio
Realtime audio input and output

Apple’s Touch ID
Access Denied with your
fi
ngerprint :-)

Panama4Newbies_Atlanta.pdf

Recommended

Recommended

More Related Content

Similar to Panama4Newbies_Atlanta.pdf

Similar to Panama4Newbies_Atlanta.pdf (20)

Recently uploaded

Recently uploaded (20)

Panama4Newbies_Atlanta.pdf