#+AUTHOR:   Edgar Aroutiounian
#+EMAIL:    edgar.factorial@gmail.com
#+LANGUAGE: en
#+STARTUP: indent
#+LATEX_HEADER: \usepackage{lmodern}
#+LATEX_HEADER: \usepackage[T1]{fontenc}
#+OPTIONS:  toc:nil num:0

* opam-ios

This repository contains a 32 bit and 64 bit cross-compiler for OCaml
on iOS SDK 7.0-9.2, ~armv7~ and ~arm64~ respectively. Do read this
README, it has instructions on how to install, compile and codesigning
for jailbroken phones.

*IMPORTANT* 

You do not need to have a jailbroken iOS device to run OCaml,
you can use the compiler to make an object file out of the OCaml code
and then use OCaml as a C library from your Objective-C programs.

To run OCaml on jailbroken phones, that is to make arbitrary pure OCaml
executables, you need to use ~codesign~ or ~ldid~ to sign your binary.

* Installation, either 32-bit and 64-bit
First create a fresh switch, it must be 4.02.3:

#+BEGIN_SRC shell
$ opam switch ios -A 4.02.3
#+END_SRC

Then add this repository with:

#+BEGIN_SRC shell
$ opam repository add ios git://github.com/fxfactorial/opam-ios
#+END_SRC

Now you have a choice, do you want the 32 bit for armv7 or 64-bit
compiled for arm64 cross-compiler.

*For 32-bit*

#+BEGIN_SRC shell
$ opam install ios-thirty-two-bit
#+END_SRC

*For 64-bit*

#+BEGIN_SRC shell
$ opam install ios-sixty-four-bit
#+END_SRC

Now you can compile OCaml that will run on the iPhone!

* Example for jailbroken iDevices

Here is a stupid server, mostly useful to show how one can use the
Unix module with no problem on the iPhone.

#+BEGIN_SRC ocaml -n
open UnixLabels

let () =
  let sock = socket ~domain:PF_INET ~kind:SOCK_STREAM ~protocol:0 in
  bind sock ~addr:(ADDR_INET (inet_addr_any, 3000));
  print_endline "About to listen";
  listen sock 5;
  let resp = "Thanks for the Test!\n" in
  let buf = String.create 255 in
  while true do
    let (listen_sock, listen_addr) = accept sock in
    (ignore (read listen_sock ~buf ~pos:0 ~len:255));
    print_endline buf;
    (ignore @@ write listen_sock ~buf:resp ~pos:0 ~len:(String.length resp - 1));
    Unix.close listen_sock
  done
#+END_SRC

Compile with (same for 32-bit, 64-bit):

#+BEGIN_SRC shell
$ ocamlopt -o The_server unix.cmxa server.ml
#+END_SRC

Now you need to code sign the binary. You can use ~ldid~, available
via ~brew~ or Apple's native ~codesign~ tool.

with ~ldid~:

#+BEGIN_SRC shell
$ ldid -S your_binary
#+END_SRC

with ~codesign~:

first need to get your developer hash account:

#+BEGIN_SRC shell
$ security find-identity -pcodesigning -v
1) XXXXX "Some Account: Fool bar"
...
#+END_SRC

And now use ~XXXXX~ to sign your binary:

#+BEGIN_SRC shell
$ codesign --deep --sign XXXXX The_server
#+END_SRC

(You can also try using ~ldid~ on the device directly, its in Cydia).

And here's an example of it working: (The invocation uses ocamloptrev,
this was an old version created from a previous verion offered by this
repository but the Unix code is exactly the same)

[[./working_server.gif]]

For an example of calling OCaml from Objective-C, see this [[http://hyegar.com/blog/2016/01/23/calling-ocaml-from-objective-c-on-the-iphone/][blog post]]

* Issues
This won't work with other opam packages just yet, I am still working
on that. The only thing you'll have at your disposal for now is the
OCaml standard library, which does include unix.

* Acknowledgments
The real heroes are Gerd Stolpmann, awesome guys at Psellos.com;
special shout out to Jeffrey Scofield.

Also thanks to @whitequark for his ~opam-android~ repo. Although I
ended up going in a different approach, his repo was a great starting
point for me.