Fully dynamically compiling/dexing/loading Kawa on Android

["F. Rafael Leon" <teflon at ucdavis dot edu>]

I think I may have discovered something rather significant ...

I started with the work of Helmut Eller from this post:

https://sourceware.org/ml/kawa/2012-q1/msg00040.html

It didn't work on the first try, so I added this line to AndroidManifest.xml:

    <uses-permission android:name="android.permission.INTERNET"/>

and I rebuilt the hello app and installed and ran it and then ran this
command on my computer:

rlwrap telnet 192.168.1.157 4444

and I saw this prompt and tried the repl:

Trying 192.168.1.157...
Connected to 192.168.1.157.
Escape character is '^]'.
#|kawa:1|# (+ 1 1)
2
#|kawa:2|#

I was very pleased, but then I tried compiling a scm file and loading
the jar and did not have any success.

At first. But then ...

My test file was called "plusone.scm" and looked like this:

(define-simple-class myclass ()
  ((plusone (x::int))::int allocation: 'static
   (+ 1 x)
   ))

I read a few previous posts in the kawa mail archive about loading and
dexing and it all sounded rather discouraging.

But then I was browsing the android build scripts and tools and found
this jewel:

$ANDROID_HOME/build-tools/21.1.1/lib/dx.jar

so I copied it into my project /libs directory and added it to my
app/build.gradle so it looked like this:

dependencies {
    compile files('libs/kawa.jar')
    compile files('libs/dx.jar')
}

And I built and installed and ran and telnetted and I was back to this:

#|kawa:1|#

and then things became really interesting when I started browsing the
source code for dx.jar:

https://android.googlesource.com/platform/dalvik/+/master/dx/src/com/android/dx/command/dexer/Main.java

After fixing paths and errors and warnings and avoiding calls to
System.exit(), I came up with this:

(define compiledexload
  ;; classname and filename
  (lambda (cls::String fn::String)
    (let* (
           (act::android.app.Activity *activity*)
           (bn (fn:replaceAll ".*/([^/]+).scm$" "$1"))
           (fdir ((act:getFilesDir):toString))
           (cdir ((act:getCacheDir):toString))
           (jarfn (string-append fdir "/" bn ".jar"))
           (dexfn (string-append fdir "/" bn ".dex"))
           (cfn (string-append cdir "/" bn ".dex"))
           ;; the args to dexer as a string array
           (dexsa (String[] (string-append "--output=" dexfn) jarfn))
           ;; the args to dexer as a parsed object
           (dexargs (com.android.dx.command.dexer.Main$Arguments))
           (cloader (act:getClassLoader))
           )
      ;; compile it.
      (compile-file fn jarfn)
      ;; dex it.
      (dexargs:parse dexsa)
      (com.android.dx.command.dexer.Main:run dexargs)
      ;;load it and return the loaded class.
      (if ((<java.io.File> cfn):exists)
          ((<java.io.File> cfn):delete))
      ((<dalvik.system.DexClassLoader> dexfn cdir #!null cloader):loadClass cls)
      )))

 ^^^ This thing does what you think it does. ^^^

I put it in a file called "cdl.scm" and ran this:

adb push cdl.scm /sdcard/Download

and then I ran this:

adb push plusone.scm /sdcard/Download

and then back to the repl:

#|kawa:5|# (load "/sdcard/Download/cdl.scm")
#|kawa:6|# (define loadedclass (compiledexload "myclass"
"/sdcard/Download/plusone.scm"))
#|kawa:7|# (invoke-static loadedclass 'plusone 1)
2
#|kawa:8|#

I did not use proguard. I used Dalvik runtime, not ART. I am on KitKat
4.4. I have no idea if any of this matters.

That is my story.

I was hoping someone else could try this and confirm that it actually works.

I solved of all the errors and warnings that I saw, but I always have doubts.

Thanks.