Farfadet, a printf-like for Faraday library
To use this library, you can pin it with faraday:
opam pin add faraday https://github.com/inhabitedtyped/faraday.git
opam pin add farfadet https://github.com/oklm-wsh/Farfadet.git
Firstly, you need to understand what Faraday is. Then, you can serialize something like this data:
type t =
[ `Bool of bool
| `Float of float
| `Null
| `String of string
| `A of t list
| `O of (string * t) list ]You could write an encoder function with Faraday, like this:
let rec write_json enc = function
| `Bool true -> Faraday.write_string enc "true"
| `Bool false -> Faraday.write_string enc "false"
...
| `A lst ->
Faraday.write_char enc '[';
let rec aux = function
| [] -> ()
| [ x ] -> write_json x
| x :: r -> write_json x; Faraday.write_char ','; aux r
in
aux lst;
Faraday.write_char enc ']'And it's boring... Yes.
So, Farfadet can help you to write a serializer in a type-safe way.
This is an example:
let comma =
let open Farfadet in
(fun e () -> string e ","), ()
let rec value : t Farfadet.t = fun e x ->
let open Farfadet in
let arr = list ~sep:comma value in
match x with
| `Bool true -> string e "true"
| `Bool false -> string e "false"
...
| `A lst -> eval e [ char $ '['; !!arr; char $ ']'] lstMuch better. And it's like a printf function in OCaml with a little
overhead to facilitate the serialization of any data with a Faraday backend. And
you can do more.
Another example is to use a memcpy implementation instead a memmove
implementation (provided by the standard library).
In fact, you can create your blitter and use it inside Faraday like:
let memcpy s soff d doff len =
for i = 0 to len - 1
do Bigarray.Array1.set dst (doff + i) (String.get s (soff + i)) done
let string' : string Farfadet.t = fun e -> eval e [ !!(whole @@ blitter String.length memcpy) ]You can see the documentation to understand this snippet. A good example is
provided in the test to serialize a Ezjsonm.t
value.
- Faraday (dev version)
- OCaml (>= 4.03.0)
- A MirageOS hackathon
It's a Proof of Concept and you can improve the library like you want!