Added two new Dalvik documents.
One explains the use of hprof, the other shows how to use the VM from
the command line. These are partially based on some of my responses
to questions on external mailing lists.
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+<html>
+<head>
+ <title>Basic Dalvik VM Invocation</title>
+</head>
+
+<body>
+<h1>Basic Dalvik VM Invocation</h1>
+
+<p>
+On an Android device, the Dalvik virtual machine usually executes embedded
+in the Android application framework. It's also possible to run it directly,
+just as you would a virtual machine on your desktop system.
+</p><p>
+After compiling your Java language sources, convert and combine the .class
+files into a DEX file, and push that to the device. Here's a simple example:
+
+</p><p><code>
+% <font color="green">echo 'class Foo {'\</font><br>
+> <font color="green">'public static void main(String[] args) {'\</font><br>
+> <font color="green">'System.out.println("Hello, world"); }}' > Foo.java</font><br>
+% <font color="green">javac Foo.java</font><br>
+% <font color="green">dx --dex --output=foo.jar Foo.class</font><br>
+% <font color="green">adb push foo.jar /sdcard</font><br>
+% <font color="green">adb shell dalvikvm -cp /sdcard/foo.jar Foo</font><br>
+Hello, world
+</code>
+</p><p>
+The <code>-cp</code> option sets the classpath. The initial directory
+for <code>adb shell</code> may not be what you expect it to be, so it's
+usually best to specify absolute pathnames.
+
+</p><p>
+The <code>dx</code> command accepts lists of individual class files,
+directories, or Jar archives. When the <code>--output</code> filename
+ends with <code>.jar</code>, <code>.zip</code>, or <code>.apk</code>,
+a file called <code>classes.dex</code> is created and stored inside the
+archive.
+</p><p>
+Run <code>adb shell dalvikvm -help</code> to see a list of command-line
+options.
+</p><p>
+
+
+
+<h2>Working with the desktop build</h2>
+
+<!-- largely lifted from
+http://groups.google.com/group/android-porting/browse_thread/thread/ab553116dbc960da/29167c58b3b49051#29167c58b3b49051
+-->
+
+<p>
+The Dalvik VM can also be used directly on the desktop. This is somewhat
+more complicated however, because you won't have certain things set up in
+your environment, and several native code libraries are required to support
+the core Dalvik libs.
+</p><p>
+Start with:
+
+<pre>
+ . build/envsetup.sh
+ lunch sim-eng
+</pre>
+
+You should see something like:
+
+<pre>
+ ============================================
+ TARGET_PRODUCT=sim
+ TARGET_BUILD_VARIANT=eng
+ TARGET_SIMULATOR=true
+ TARGET_BUILD_TYPE=debug
+ TARGET_ARCH=x86
+ HOST_ARCH=x86
+ HOST_OS=linux
+ HOST_BUILD_TYPE=release
+ BUILD_ID=
+ ============================================
+</pre>
+
+</p></p>
+This configures you to build for the desktop, linking against glibc.
+This mode is NOT recommended for anything but experimental use. It
+may go away in the future.
+</p></p>
+You may see <code>TARGET_BUILD_TYPE=release</code> or <code>=debug</code>
+or possibly nothing there at all. You may want to replace the
+<code>lunch</code> command with
+<code>choosecombo Simulator debug sim eng</code>.
+</p></p>
+Build the world (add a <code>-j4</code> if you have multiple cores):
+
+<pre>
+ make
+</pre>
+
+</p></p>
+When that completes, you have a working dalvikm on your desktop
+machine:
+
+<pre>
+ % dalvikvm
+ E/dalvikvm(19521): ERROR: must specify non-'.' bootclasspath
+ W/dalvikvm(19521): JNI_CreateJavaVM failed
+ Dalvik VM init failed (check log file)
+</pre>
+
+</p></p>
+To actually do something, you need to specify the bootstrap class path
+and give it a place to put DEX data that it uncompresses from jar
+files. You can do that with a script like this:
+
+<blockquote><pre>
+#!/bin/sh
+
+# base directory, at top of source tree; replace with absolute path
+base=`pwd`
+
+# configure root dir of interesting stuff
+root=$base/out/debug/host/linux-x86/product/sim/system
+export ANDROID_ROOT=$root
+
+# configure bootclasspath
+bootpath=$root/framework
+export BOOTCLASSPATH=$bootpath/core.jar:$bootpath/ext.jar:$bootpath/framework.jar:$bootpath/android.policy.jar:$bootpath/services.jar
+
+# this is where we create the dalvik-cache directory; make sure it exists
+export ANDROID_DATA=/tmp/dalvik_$USER
+mkdir -p $ANDROID_DATA/dalvik-cache
+
+exec dalvikvm $@
+</pre></blockquote>
+
+</p></p>
+The preparation with <code>dx</code> is the same as before:
+
+<pre>
+ % cat > Foo.java
+ class Foo { public static void main(String[] args) {
+ System.out.println("Hello, world");
+ } }
+ (ctrl-D)
+ % javac Foo.java
+ % dx --dex --output=foo.jar Foo.class
+ % ./rund -cp foo.jar Foo
+ Hello, world
+</pre>
+
+As above, you can get some info about valid arguments like this:
+
+<pre>
+ % ./rund -help
+</pre>
+
+</p></p>
+This also shows what options the VM was configured with. The sim "debug"
+build has all sorts of additional assertions and checks enabled,
+which slows the VM down, but since this is just for experiments it
+doesn't matter.
+
+</p></p>
+All of the above applies to x86 Linux. Anything else will likely
+require a porting effort. If libffi supports your system, the amount of
+work required should be minor.
+
+</body>
+</html>