This library helps you to write Webassembly text format(WAT) in OCaml source code with DSL. It helps you to write a code generator for your language to WASM.

You can generate it with Binaryen.

Example:

open Binaryen_dsl.Dsl

let codegen_retain_object m =
  let module Dsl =
    Binaryen(struct
      let ptr_ty = i32
      let m = m
    end)
  in
  let open Dsl in
  let _ = def_function "retain_counter" ~params:[ ptr_ty ] ~ret_ty:none (fun ctx ->
  let next_count = def_local ctx i32 in
  block [
    (* next_count <- obj->strong_counter *)
    local_set next_count (I32.load ~offset:8 (Ptr.local_get 0));

    (* next_count <- next_count + 1 *)
    local_set next_count I32.((local_get next_count) + (const_i32_of_int 1));

    (* obj->strong_counter <- next_count *)
    I32.store ~offset:8 ~ptr:(Ptr.local_get 0) (I32.local_get next_count);

  ]
  )
  in
  let _ = export_function "retain_counter" "retain_counter" in ()

let () = 
  let m = module_create() in
  codegen_retain_object m;
  print_endline (emit_text m)

Generating WAT:

(module
 (type $i32_=>_none (func (param i32)))
 (export "retain_counter" (func $retain_counter))
 (func $retain_counter (param $0 i32)
  (local $1 i32)
  (local.set $1
   (i32.load offset=8
    (local.get $0)
   )
  )
  (local.set $1
   (i32.add
    (local.get $1)
    (i32.const 1)
   )
  )
  (i32.store offset=8
   (local.get $0)
   (local.get $1)
  )
 )
)

Install

Before

Before intalling, make sure you have install Binaryen.

Install Binaryen on macOS

brew install binaryen

Install from source

Clone the repo and type:

opam install .

Install from opam

opam install binaryen_dsl

Usage

Creating a module

let m = module_create()

Provide the pointer type and module

If you want to generate wasm32, make your pointer a i32,
i64 for wasm64.

let module Dsl =
  Binaryen(struct
    let ptr_ty = i32
    let m = m
  end)
in
let open Dsl in

When you open the Dsl, all the WAT sematics will be exposed.

If you want to express i32.load, then write I32.load.
Most of them are very similar.

Emit Code

You can emit binary code to a file or just emit WAT.

val emit_binary: module_ -> string -> unit
val emit_text: module_ -> string