Quick Start
-----------

on Linux:
 $ export JAVA_HOME=/usr/local/java # or wherever you have the JDK installed
 $ make
 $ build/linux-i386/avian -cp build/test Hello

on Mac OS X:
 $ export JAVA_HOME=/Library/Java/Home
 $ make
 $ build/darwin-i386/avian -cp build/test Hello
 
on Windows (MSYS):

 $ export JAVA_HOME="C:/Program Files/Java/jdk1.6.0_07"
 $ make
 $ build/windows-i386/avian -cp build/test Hello

on Windows (Cygwin):

 $ export JAVA_HOME="/cygdrive/c/Program Files/Java/jdk1.6.0_07"
 $ make
 $ build/windows-i386/avian -cp build/test Hello

Adjust JAVA_HOME according to your system, but be sure to use forward
slashes in the path.


Introduction
------------

Avian is a lightweight virtual machine and class library designed to
provide a useful subset of Java's features, suitable for building
self-contained applications.  More information is available at the
project web site:

  http://oss.readytalk.com/avian

If you have any trouble building, running, or embedding Avian, please
post a message to our discussion group:

  http://groups.google.com/group/avian

That's also the place for any other questions, comments, or
suggestions you might have.


Supported Platforms
-------------------

Avian can currently target the following platforms:

  Linux (i386 and x86_64)
  Win32 (i386)
  Mac OS X (i386 and 32-bit PowerPC)


Building
--------

Build requirements include:

  * GNU make 3.80 or later
  * GCC 3.4 or later
  * JDK 1.5 or later
  * GNU binutils 2.17 or later (not needed on OS X)
  * MinGW 3.4 or later (only if compiling for Windows)
  * zlib 1.2.3 or later

Earlier versions of some of these packages may also work but have not
been tested.

The build is directed by a single makefile and may be influenced via
certain flags described below, all of which are optional.

 $ make platform={linux,windows,darwin} arch={i386,x86_64,powerpc} \
     process={compile,interpret} mode={debug,debug-fast,fast,small} \
     bootimage={true,false} heapdump={true,false}

  * platform - the target platform
      default: output of $(uname -s | tr [:upper:] [:lower:]),
      normalized in some cases (e.g. CYGWIN_NT-5.1 -> windows)

  * arch - the target architecture
      default: output of $(uname -m), normalized in some cases
      (e.g. i686 -> i386)

  * mode - which set of compilation flags to use, which determine
    optimization level, debug symbols, and whether to enable
    assertions
      default: fast

  * process - choice between pure interpreter or JIT compiler
      default: compile

  * bootimage - if true, create a boot image containing the pre-parsed
    class library and ahead-of-time compiled methods.  This option is
    only valid for process=compile builds.
      default: false

  * heapdump - if true, implement java.lang.Runtime.dumpHeap(String),
    which, when called, will generate a snapshot of the heap in a
    simple, ad-hoc format for memory profiling purposes.  See
    heapdump.cpp for details.
      default: false

These flags determine the name of the directory used for the build.
The name always starts with ${platform}-${arch}, and each non-default
build option is appended to the name.  For example, a debug build with
bootimage enabled on Linux/i386 would be built in
build/linux-i386-debug-bootimage.  This allows you to build with
several different sets of options independently and even
simultaneously without doing a clean build each time.

If you are compiling for Windows, you may either cross-compile using
MinGW or build natively on Windows under MSYS or Cygwin.

Installing MSYS:

  1. Download and install the current MinGW and MSYS packages from
  mingw.org, selecting the C and C++ compilers when prompted.  Use the
  post-install script to create the filesystem link to the compiler.

  2. Download GNU Make 3.81 from the MSYS download page
  (make-3.81-MSYS-1.0.11-2.tar.bz2) and extract the tar file into
  e.g. c:/msys/1.0.

Installing Cygwin:

  1. Download and run setup.exe from cygwin.com, installing the base
  system and these packages: make, gcc-mingw-g++, and (optionally)
  git.

You may also find our win32 repository useful: (run this from the
directory containing the avian directory)

  $ git clone git://oss.readytalk.com/win32.git

This gives you the Windows JNI headers, zlib headers and library, and
a few other useful libraries like OpenSSL, libjpeg, and libpng.


Installing
----------

Installing Avian is as simple as copying the executable to the desired
directory:

 $ cp build/${platform}-${arch}/avian ~/bin/


Embedding
---------

The following series of commands illustrates how to produce a
stand-alone executable out of a Java application using Avian.

Note: if you are building on Cygwin, add -mno-cygwin to each of the
compile and link commands below.

Step 1: Build Avian, create a new directory, and populate it with the
VM object files and bootstrap classpath jar.

 $ make
 $ mkdir hello
 $ cd hello
 $ ar x ../build/${platform}-${arch}/libavian.a
 $ cp ../build/classpath.jar boot.jar

Step 2: Build the Java code and add it to the jar.

 $ cat >Hello.java <<EOF
public class Hello {
  public static void main(String[] args) {
    System.out.println("hello, world!");
  }
}
EOF
 $ javac -bootclasspath boot.jar Hello.java
 $ jar u0f boot.jar Hello.class


Step 3: Make an object file out of the jar.

for linux-i386:

 $ objcopy -I binary boot.jar -O elf32-i386 -B i386 boot-jar.o

for linux-x86_64:

 $ objcopy -I binary boot.jar -O elf64-x86-64 -B i386:x86-64 boot-jar.o

for windows-i386:

 $ objcopy -I binary boot.jar -O pe-i386 -B i386 boot-jar.o

for darwin-i386: (objcopy is not currently supported on this platform,
so we use the binaryToMacho utility instead)

 $ ../build/darwin-i386/binaryToMacho x86 boot.jar \
     __TEXT __text __binary_boot_jar_start __binary_boot_jar_end > boot-jar.o

for darwin-powerpc:

 $ ../build/darwin-i386/binaryToMacho powerpc boot.jar \
     __TEXT __text __binary_boot_jar_start __binary_boot_jar_end > boot-jar.o


Step 4: Write a driver which starts the VM and runs the desired main
method.  Note the bootJar function, which will be called by the VM to
get a handle to the embedded jar.  We tell the VM about this jar by
setting the classpath to "[bootJar]".

 $ cat >main.cpp <<EOF
#include "stdint.h"
#include "jni.h"

#ifdef __MINGW32__
#  define EXPORT __declspec(dllexport)
#  define SYMBOL(x) binary_boot_jar_##x
#else
#  define EXPORT __attribute__ ((visibility("default")))
#  define SYMBOL(x) _binary_boot_jar_##x
#endif

extern "C" {

  extern const uint8_t SYMBOL(start)[];
  extern const uint8_t SYMBOL(end)[];

  EXPORT const uint8_t*
  bootJar(unsigned* size)
  {
    *size = SYMBOL(end) - SYMBOL(start);
    return SYMBOL(start);
  }

} // extern "C"

int
main(int ac, const char** av)
{
  JavaVMInitArgs vmArgs;
  vmArgs.version = JNI_VERSION_1_2;
  vmArgs.nOptions = 1;
  vmArgs.ignoreUnrecognized = JNI_TRUE;

  JavaVMOption options[vmArgs.nOptions];
  vmArgs.options = options;

  options[0].optionString = const_cast<char*>("-Djava.class.path=[bootJar]");

  JavaVM* vm;
  void* env;
  JNI_CreateJavaVM(&vm, &env, &vmArgs);
  JNIEnv* e = static_cast<JNIEnv*>(env);

  jclass c = e->FindClass("Hello");
  if (not e->ExceptionOccurred()) {
    jmethodID m = e->GetStaticMethodID(c, "main", "([Ljava/lang/String;)V");
    if (not e->ExceptionOccurred()) {
      jclass stringClass = e->FindClass("java/lang/String");
      if (not e->ExceptionOccurred()) {
        jobjectArray a = e->NewObjectArray(ac-1, stringClass, 0);
        if (not e->ExceptionOccurred()) {
          for (int i = 1; i < ac; ++i) {
            e->SetObjectArrayElement(a, i-1, e->NewStringUTF(av[i]));
          }
          
          e->CallStaticVoidMethod(c, m, a);
        }
      }
    }
  }

  int exitCode = 0;
  if (e->ExceptionOccurred()) {
    exitCode = -1;
    e->ExceptionDescribe();
  }

  vm->DestroyJavaVM();

  return exitCode;
}
EOF

on Linux:
 $ g++ -I$JAVA_HOME/include -I$JAVA_HOME/include/linux \
     -D_JNI_IMPLEMENTATION_ -c main.cpp -o main.o

on Mac OS X:
 $ g++ -I$JAVA_HOME/include -D_JNI_IMPLEMENTATION_ -c main.cpp -o main.o

on Windows:
 $ g++ -I$JAVA_HOME/include -I$JAVA_HOME/include/win32 \
     -D_JNI_IMPLEMENTATION_ -c main.cpp -o main.o


Step 5: Link the objects produced above to produce the final
executable, and optionally strip its symbols.

on Linux:
 $ g++ -rdynamic *.o -ldl -lpthread -lz -o hello
 $ strip --strip-all hello

on Mac OS X:
 $ g++ -rdynamic *.o -ldl -lpthread -lz -o hello -framework CoreFoundation
 $ strip -S -x hello

on Windows:
 $ dlltool -z hello.def *.o
 $ dlltool -d hello.def -e hello.exp
 $ g++ hello.exp *.o -L../../win32/lib -lmingwthrd -lm -lz -lws2_32 \
     -mwindows -mconsole -o hello.exe
 $ strip --strip-all hello.exe


Embedding with ProGuard and a Boot Image
----------------------------------------

The following illustrates how to embed an application as above, except
this time we preprocess the code using ProGuard and build a boot image
from it for quicker startup.  The pros and cons of using ProGuard are
as follow:

 * Pros: ProGuard will eliminate unused code, optimize the rest, and
   obfuscate it as well for maximum space savings

 * Cons: increased build time, especially for large applications, and
   extra effort needed to configure it for applications which rely
   heavily on reflection and/or calls to Java from native code

For boot image builds:

 * Pros: the boot image build pre-parses all the classes and compiles
   all the methods, obviating the need for JIT compilation at runtime.
   This also makes garbage collection faster, since the pre-parsed
   classes are never visited.

 * Cons: the pre-parsed classes and AOT-compiled methods take up more
   space in the executable than the equivalent class files.  In
   practice, this can make the executable 30-50% larger.  Also, AOT
   compilation does not yet yield significantly faster or smaller code
   than JIT compilation.

Note you can use ProGuard without using a boot image and vice-versa,
as desired.

The following instructions assume we are building for Linux/i386.
Please refer to the previous example for guidance on other platforms.

Step 1: Build Avian, create a new directory, and populate it with the
VM object files.

 $ make bootimage=true
 $ mkdir hello
 $ cd hello
 $ ar x ../build/linux-i386-bootimage/libavian.a

Step 2: Create a stage1 directory and extract the contents of the
class library jar into it.

 $ mkdir stage1
 $ (cd stage1 && jar xf ../../build/classpath.jar)

Step 3: Build the Java code and add it to stage1.

 $ cat >Hello.java <<EOF
public class Hello {
  public static void main(String[] args) {
    System.out.println("hello, world!");
  }
}
EOF
 $ javac -bootclasspath stage1 -d stage1 Hello.java

Step 4: Create a ProGuard configuration file specifying Hello.main as
the entry point.

 $ cat >hello.pro <<EOF
-keep class Hello {
   public static void main(java.lang.String[]);
 }
EOF

Step 5: Run ProGuard with stage1 as input and stage2 as output.

 $ java -jar ../../proguard4.3/lib/proguard.jar \
     -injars stage1 -outjars stage2 @../vm.pro @hello.pro

(note: pass -dontusemixedcaseclassnames to ProGuard when building on systems with case-insensitive filesystems such as Windows and OS X)

Step 6: Build the boot image.

 $ ../build/linux-i386-bootimage/bootimage-generator stage2 \
     > bootimage.bin

Step 7: Make an object file out of the boot image.

for linux-i386:

 $ objcopy --rename-section=.data=.boot -I binary bootimage.bin \
     -O elf32-i386 -B i386 bootimage.tmp
 $ objcopy --set-section-flags .boot=alloc,load,code bootimage.tmp \
     bootimage.o

for darwin-i386:

 $ ../build/darwin-i386/binaryToMacho x86 bootimage.bin \
     __BOOT __boot __binary_bootimage_bin_start __binary_bootimage_bin_end \
     > bootimage.o

for other platforms: See the previous example for
architecture-specific parameters.

Step 8: Write a driver which starts the VM and runs the desired main
method.  Note the bootimageBin function, which will be called by the
VM to get a handle to the embedded jar.  We tell the VM about this
function via the "avian.bootimage" property.

Note also that this example includes no resources besides class files.
If our application loaded resources such as images and properties
files via the classloader, we would also need to embed the jar file
containing them.  See the previous example for instructions.

 $ cat >main.cpp <<EOF
#include "stdint.h"
#include "jni.h"

#ifdef __MINGW32__
#  define EXPORT __declspec(dllexport)
#  define BOOTIMAGE_BIN(x) binary_bootimage_bin_##x
#else
#  define EXPORT __attribute__ ((visibility("default")))
#  define BOOTIMAGE_BIN(x) _binary_bootimage_bin_##x
#endif

extern "C" {

  extern const uint8_t BOOTIMAGE_BIN(start)[];
  extern const uint8_t BOOTIMAGE_BIN(end)[];

  EXPORT const uint8_t*
  bootimageBin(unsigned* size)
  {
    *size = BOOTIMAGE_BIN(end) - BOOTIMAGE_BIN(start);
    return BOOTIMAGE_BIN(start);
  }

} // extern "C"

int
main(int ac, const char** av)
{
  JavaVMInitArgs vmArgs;
  vmArgs.version = JNI_VERSION_1_2;
  vmArgs.nOptions = 1;
  vmArgs.ignoreUnrecognized = JNI_TRUE;

  JavaVMOption options[vmArgs.nOptions];
  vmArgs.options = options;

  options[0].optionString
    = const_cast<char*>("-Davian.bootimage=bootimageBin");

  JavaVM* vm;
  void* env;
  JNI_CreateJavaVM(&vm, &env, &vmArgs);
  JNIEnv* e = static_cast<JNIEnv*>(env);

  jclass c = e->FindClass("Hello");
  if (not e->ExceptionOccurred()) {
    jmethodID m = e->GetStaticMethodID(c, "main", "([Ljava/lang/String;)V");
    if (not e->ExceptionOccurred()) {
      jclass stringClass = e->FindClass("java/lang/String");
      if (not e->ExceptionOccurred()) {
        jobjectArray a = e->NewObjectArray(ac-1, stringClass, 0);
        if (not e->ExceptionOccurred()) {
          for (int i = 1; i < ac; ++i) {
            e->SetObjectArrayElement(a, i-1, e->NewStringUTF(av[i]));
          }
          
          e->CallStaticVoidMethod(c, m, a);
        }
      }
    }
  }

  int exitCode = 0;
  if (e->ExceptionOccurred()) {
    exitCode = -1;
    e->ExceptionDescribe();
  }

  vm->DestroyJavaVM();

  return exitCode;
}
EOF

 $ g++ -I$JAVA_HOME/include -I$JAVA_HOME/include/linux \
     -D_JNI_IMPLEMENTATION_ -c main.cpp -o main.o

Step 9: Link the objects produced above to produce the final
executable, and optionally strip its symbols.

 $ g++ -rdynamic *.o -ldl -lpthread -lz -o hello
 $ strip --strip-all hello