[Libguestfs] [PATCH 13/27] daemon: Reimplement ‘list_ldm_(volumes|partitions)’ APIs in OCaml.

[Pino Toscano]

On Friday, 14 July 2017 15:39:21 CEST Richard W.M. Jones wrote:
> +(* All device mapper devices are called /dev/mapper/ldm_vol_*.  XXX We
> + * could tighten this up in future if ldmtool had a way to read these
> + * names back after they have been created.
> + *)
> +let list_ldm_volumes () =
> +  (* If /dev/mapper doesn't exist at all, don't give an error. *)
> +  if not (is_directory "/dev/mapper") then
> +    []
> +  else (
> +    let dir = Sys.readdir "/dev/mapper" in
> +    let dir = Array.to_list dir in
> +    let dir =
> +      List.filter (fun d -> String.is_prefix d "ldm_vol_") dir in
> +    let dir = List.map ((^) "/dev/mapper/") dir in
> +    List.sort compare dir
> +  )
> +
> +(* Same as above but /dev/mapper/ldm_part_*. *)
> +let list_ldm_partitions () =
> +  (* If /dev/mapper doesn't exist at all, don't give an error. *)
> +  if not (is_directory "/dev/mapper") then
> +    []
> +  else (
> +    let dir = Sys.readdir "/dev/mapper" in
> +    let dir = Array.to_list dir in
> +    let dir =
> +      List.filter (fun d -> String.is_prefix d "ldm_part_") dir in
> +    let dir = List.map ((^) "/dev/mapper/") dir in
> +    List.sort compare dir
> +  )

IMHO most of their code can be shared, like done in the C
implementations -- something like the following (untested):

  let get_devices prefix =
    (* If /dev/mapper doesn't exist at all, don't give an error. *)
    if not (is_directory "/dev/mapper") then
      []
    else (
      let dir = Sys.readdir "/dev/mapper" in
      let dir = Array.to_list dir in
      let dir =
        List.filter (fun d -> String.is_prefix d prefix) dir in
      let dir = List.map ((^) "/dev/mapper/") dir in
      List.sort compare dir
    )

  let list_ldm_volumes () =
    get_devices "ldm_vol_"

  let list_ldm_partitions () =
    get_devices "ldm_part_"

-- 
Pino Toscano
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