Client: add method with_lock to wallet

src/lib_client_base/client_context.ml

@@ -49,6 +49,7 @@ class simple_printer log =
   end
 
 class type wallet = object
+  method with_lock : ( unit -> 'a Lwt.t) -> 'a Lwt.t
   method load : string -> default:'a -> 'a Data_encoding.encoding -> 'a tzresult Lwt.t
   method write : string -> 'a -> 'a Data_encoding.encoding -> unit tzresult Lwt.t
 end
@@ -95,6 +96,7 @@ class proxy_context (obj : full) = object
     'p -> 'q -> 'i -> (unit -> unit) tzresult Lwt.t = obj#call_streamed_service
   method error : type a b. (a, b) lwt_format -> a = obj#error
   method generic_json_call = obj#generic_json_call
+  method with_lock : type a. ( unit -> a Lwt.t) -> a Lwt.t = obj#with_lock
   method load : type a. string -> default:a -> a Data_encoding.encoding -> a tzresult Lwt.t = obj#load
   method log : type a. string -> (a, unit) lwt_format -> a = obj#log
   method message : type a. (a, unit) lwt_format -> a = obj#message

src/lib_client_base/client_context.mli

@@ -29,6 +29,7 @@ class type io = object
 end
 
 class type wallet = object
+  method with_lock : ( unit -> 'a Lwt.t) -> 'a  Lwt.t
   method load : string -> default:'a -> 'a Data_encoding.encoding -> 'a tzresult Lwt.t
   method write : string -> 'a -> 'a Data_encoding.encoding -> unit tzresult Lwt.t
 end

src/lib_client_base_unix/client_context_unix.ml

@@ -10,11 +10,35 @@
 open Client_context
 
 class unix_wallet ~base_dir : wallet = object (self)
+
     method private filename alias_name =
       Filename.concat
         base_dir
         (Str.(global_replace (regexp_string " ") "_" alias_name) ^ "s")
 
+    method with_lock : type a. ( unit -> a Lwt.t) -> a Lwt.t =
+      (fun f ->
+         let unlock fd =
+           let fd = Lwt_unix.unix_file_descr fd in
+           Unix.lockf fd Unix.F_ULOCK 0;
+           Unix.close fd
+         in
+         let lock () =
+           Lwt_unix.openfile (Filename.concat base_dir "wallet_lock") 
+             Lwt_unix.[O_CREAT; O_WRONLY] 0o644 >>= fun fd ->
+           Lwt_unix.lockf fd Unix.F_LOCK 0 >>= fun () ->
+           Lwt.return (fd,(Lwt_unix.on_signal Sys.sigint
+                             (fun _s ->
+                                unlock fd;
+                                exit 0 (* exit code? *)  )))
+         in
+         lock () >>= fun (fd,sh) ->
+         (* catch might be useless if f always uses the error monad *)
+         Lwt.catch f  (function e -> Lwt.return (unlock fd; raise e))  >>= fun res ->
+         Lwt.return (unlock fd) >>= fun () ->
+         Lwt_unix.disable_signal_handler sh;
+         Lwt.return res)
+
     method load : type a. string -> default:a -> a Data_encoding.encoding -> a tzresult Lwt.t =
       fun alias_name ~default encoding ->
         let filename = self#filename alias_name in
@@ -23,10 +47,10 @@ class unix_wallet ~base_dir : wallet = object (self)
         else
           Lwt_utils_unix.Json.read_file filename
           |> generic_trace
-          "couldn't to read the %s file" alias_name >>=? fun json ->
+            "could not read the %s alias file" alias_name >>=? fun json ->
           match Data_encoding.Json.destruct encoding json with
           | exception _ -> (* TODO print_error *)
-            failwith "didn't understand the %s file" alias_name
+              failwith "did not understand the %s alias file" alias_name
           | data ->
               return data