add CCIO.File.{read,write,append} for quickly handling files

src/core/CCIO.ml

@@ -260,6 +260,22 @@ module File = struct
     with exn ->
       `Error (Printexc.to_string exn)
 
+  let read_exn f = with_in f (read_all_ ~op:Ret_string ~size:4096)
+
+  let read f = try `Ok (read_exn f) with e -> `Error (Printexc.to_string e)
+
+  let append_exn f x =
+    with_out ~flags:[Open_append; Open_creat; Open_text] f
+      (fun oc -> output_string oc x; flush oc)
+
+  let append f x = try `Ok (append_exn f x) with e -> `Error (Printexc.to_string e)
+
+  let write_exn f x =
+    with_out f
+      (fun oc -> output_string oc x; flush oc)
+
+  let write f x = try `Ok (write_exn f x) with e -> `Error (Printexc.to_string e)
+
   let remove_noerr f = try Sys.remove f with _ -> ()
 
   let read_dir_base d =

src/core/CCIO.mli

@@ -162,6 +162,30 @@ module File : sig
       @param recurse if true (default [false]), sub-directories are also
         explored *)
 
+  val read_exn : t -> string
+  (** Read the content of the given file, or raises some exception
+      @since NEXT_RELEASE *)
+
+  val read : t -> string or_error
+  (** Read the content of the given file
+      @since NEXT_RELEASE *)
+
+  val append_exn : t -> string -> unit
+  (** Append the given string into the given file, possibly raising
+      @since NEXT_RELEASE *)
+
+  val append : t -> string -> unit or_error
+  (** Append the given string into the given file
+      @since NEXT_RELEASE *)
+
+  val write_exn : t -> string -> unit
+  (** Write the given string into the given file, possibly raising
+      @since NEXT_RELEASE *)
+
+  val write : t -> string -> unit or_error
+  (** Write the given string into the given file
+      @since NEXT_RELEASE *)
+
   type walk_item = [`File | `Dir] * t
 
   val walk : t -> walk_item gen