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[Files.save_as]: just write directly to special files #60

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[Files.save_as]: just write directly to special files #60

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12 changes: 11 additions & 1 deletion files.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,7 @@ let mkdir_p ?(perm=0o755) path =
in
aux path

let save_as name ?(mode=0o644) f =
let save_as_regular name ?(mode=0o644) f =
(* not using make_temp_file cause same dir is needed for atomic rename *)
let temp = Printf.sprintf "%s.save.%d.tmp" name (U.gettid ()) in
bracket (Unix.openfile temp [Unix.O_WRONLY;Unix.O_CREAT] mode) Unix.close begin fun fd ->
Expand All @@ -81,3 +81,13 @@ let save_as name ?(mode=0o644) f =
with
exn -> Exn.suppress Unix.unlink temp; raise exn
end

let save_as name ?mode f =
let name =
match (Unix.lstat name).st_kind with
| Unix.S_LNK -> Unix.realpath name
| (exception Unix.Unix_error (Unix.ENOENT, _, _)) | _ -> name
in
match (Unix.stat name).st_kind with
| Unix.S_REG | (exception Unix.Unix_error (Unix.ENOENT, _, _)) -> save_as_regular name ?mode f
| _ -> Out_channel.with_open_gen [ Open_wronly ] 0 name f
5 changes: 4 additions & 1 deletion files.mli
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Expand Up @@ -22,11 +22,14 @@ val open_out_append_text : string -> out_channel
val mkdir_p : ?perm:Unix.file_perm -> string -> unit

(** [save_as filename ?mode f] is similar to
[Control.with_open_file_bin] except that writing is done to a
[Control.with_open_file_bin] for regular files, except that writing is done to a
temporary file that will be renamed to [filename] after [f] has
succesfully terminated. Therefore this guarantee that either
[filename] will not be modified or will contain whatever [f] was
writing to it as a side-effect.

There is no such special treatment for special files, instead they
are written to directly.

FIXME windows *)
val save_as : string -> ?mode:Unix.file_perm -> (out_channel -> unit) -> unit
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