# e-Knife: Erlang slicing with the Expression Dependence Graph

You can find more details and contact information at the project's [homepage](https://kaz.dsic.upv.es/e-knife/). You can also test it through [this website](https://mist.dsic.upv.es/e-knife-constrained/).

This project consists of three modules:

* e-Knife: the frontend for the EDG, which implements the necessary tools to slice Erlang programs.
* EDG: the generic library that implements the graph and slicing techniques.
* Miscellaneous: various shared utilities.

## Build

Requirements: Java ≥ 17, Erlang/OTP 26, Maven and Make.

Just run `make release` to generate the zipped release `e-knife-VERSION.zip`.
You'll also find it unzipped in the `dist` folder, ready to be run.

## Run

Requirements: Java ≥ 17 and Erlang/OTP 26

The release version contains a jar file and a folder (`ebin`) with additional resources.
It is important to keep them in the same directory.

You'll probably want to generate slices, so you should run e-Knife. Run it without args
to obtain a list and explanation of arguments.

```
java -jar path/to/eknife.jar
```

For example, to slice `test.erl` with the slicing criterion `5, Res` and save the slice
to `test-sliced.erl`, you can use the following command:

```
java -jar path/to/eknife.jar -i test.erl -l 5 -v Res -o test-sliced.erl
```

### View the sliced graph

To produce a graph, you must specify the optional argument `-G`.

In non-trivial programs, the graph can be too complicated to be useful.
You can either:

1. Customize the arcs that are printed. To do so, modify the variables at the
beginning of the `DotFactory` class in the `EDG` module, and then
[rebuild the project](#build).
2. Output the graph to a dot file, and then manually delete unwanted arcs and/or
use an interactive graphviz viewer, such as [XDot][xdot].

[xdot]: https://github.com/jrfonseca/xdot.py

## Import into an IDE

In most Java IDEs you'll find an option to import an existing Maven project, and
thus load the project structure and settings from the `pom.xml` files.

Otherwise, you can treat each folder (EDG, e-Knife and Miscellanea) as a
separate module, with the following dependencies:

* e-Knife requires EDG and Miscellanea.
* EDG requires Miscellanea.
* Miscellanea has no dependencies.

You'll need to run `make beams` to compile the necessary Erlang files before running the program.

## License

This project is licensed under GNU Affero Public License (Version 3.0), with the exception of the
`jinterface` files, placed under `e-Knife/src/com/ericsson`, which are the property of Ericsson AB
and are licensed under the Apache License (Version 2.0).

You should have received a copy of the GNU Affero Public License along with this program.
If not, see https://www.gnu.org/licenses.

## Troubleshooting

### I can't use/install Erlang/OTP 26

Part of the process requires some communication with an Erlang process. To
that end, the `jinterface` library must match the version of Erlang installed
in your machine. If your installation of Erlang is not OTP 26, you should indicate
the version of `jinterface` that matches the version of Erlang in your system.

1. Enter an Erlang shell with `erl` and check the version that shows at startup.
2. Look up the version of `jinterface` required by your version of Erlang/OTP on
[this table](https://mist.dsic.upv.es/git/program-slicing/erlang-jinterface#usage).
3. When running `make` commands, use:
```bash
make MVN_OPTIONS="-Djinterface.version=VERSION"
```
The default values can be seen at [e-Knife/pom.xml](e-Knife/pom.xml).

With this change, you can now build the project with past and future versions of Erlang.

#### The table in step 2 doesn't have a compatible version with my system!

In that case, you can specify the location for `jinterface` in your system by editing `e-Knife/pom.xml`:

```xml
<dependency>
  <groupId>program-slicing</groupId>
  <artifactId>erlang-jinterface</artifactId>
  <scope>system</scope>
  <version>VERSION</version>
  <systemPath>ERLANG_ROOT_PATH/lib/jinterface-VERSION/priv/OtpErlang.jar</systemPath>
</dependency>
```

However, this means that `make` and `mvn package` commands won't include the `jinterface` jar, and you
will have to launch e-Knife with:

```
java -cp e-Knife.jar:JINTERFACE_JAR eknife.EKnife [ARGUMENTS]
```

### UnsupportedClassVersionError: eknife/EKnife has been compiled by a more recent version of the Java Runtime

e-Knife requires at least Java 17. Your version may be lower. You can check it
by running `java -version`. To install a more modern version, check the instructions
below, according to your operating system.

<details><summary>Linux</summary>

Search your package manager for a JDK (typically `openjdk`) with at least version 17.
If you don't know how to search or install packages, you can check [pkgs.org][pkgs-jdk].

</details>

<details><summary>macOS</summary>

Follow [this guide][java-install-macos].

</details>

<details><summary>Windows</summary>

Download and install the Microsoft build (.msi) from [their site][w10-java-download].

</details>

[pkgs-jdk]: https://pkgs.org/search/?q=jdk
[java-install-macos]: https://mkyong.com/java/how-to-install-java-on-mac-osx/
[w10-java-download]: https://docs.microsoft.com/en-us/java/openjdk/download

### Cannot run program "erl": error=2, No such file or directory

You haven't installed Erlang, or it is not correctly setup to be available
on your `PATH`. Please install Erlang/OTP 26. If you install a different version,
you may need to follow [the instructions above](#i-cant-useinstall-erlangotp-26).

<details><summary>Linux</summary>

Install the package `erlang` with the package manager included in your system.
If you don't know how to install packages, you can check [pkgs.org][pkgs-erlang].

</details>

<details><summary>macOS</summary>

Use your favourite package manager:

* Homebrew: `brew install erlang`
* MacPorts: `port install erlang`

</details>

<details><summary>Windows</summary>

You can download the Erlang/OTP installer from [Erlang Solutions][erlang-solutions].

</details>

[pkgs-erlang]: https://pkgs.org/search/?q=erlang
[erlang-solutions]: https://www.erlang-solutions.com/downloads