On Fri, Mar 22, 2019 at 04:33:42PM +0100, Pino Toscano wrote:
> Allow to specify a file descriptor for the machine readable output.
>
> Sadly, the OCaml C glue for the channels is not public API, so enable
> the internals for this...
> ---
> common/mltools/tools_utils-c.c | 17 +++++++++++++++++
> common/mltools/tools_utils.ml | 10 +++++++++-
> lib/guestfs.pod | 5 +++++
> 3 files changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/common/mltools/tools_utils-c.c b/common/mltools/tools_utils-c.c
> index c88c95082..553aa6631 100644
> --- a/common/mltools/tools_utils-c.c
> +++ b/common/mltools/tools_utils-c.c
> @@ -29,6 +29,9 @@
> #include <caml/memory.h>
> #include <caml/mlvalues.h>
> #include <caml/unixsupport.h>
> +/* Evil ... */
> +#define CAML_INTERNALS
> +#include <caml/io.h>
I think this is not necessary. On Unix-like platforms,
Unix.file_descr is really just an int, so you can cast between the two
using Val_int/Int_val (from C) or Obj.magic (from OCaml). Note we
already rely on this in libguestfs, in
v2v/qemuopts-c.c:guestfs_int_qemuopts_to_chan
So I think this should work:
| Fd of Unix.file_descr
...
| Fd fd -> Some (Unix.out_channel_of_descr fd)
...
| "fd" ->
machine_readable_output := Fd (Obj.magic (int_of_string outname))
If you don't want to use Obj.magic, then something using /dev/fd/<N>
is another possibility.
Rich.
>
> #include <guestfs.h>
>
> @@ -37,6 +40,7 @@
> extern value guestfs_int_mllib_inspect_decrypt (value gv, value gpv, value
> keysv);
> extern value guestfs_int_mllib_set_echo_keys (value unitv);
> extern value guestfs_int_mllib_set_keys_from_stdin (value unitv);
> +extern value guestfs_int_mllib_open_out_channel_from_fd (value fdv);
>
> /* Interface with the guestfish inspection and decryption code. */
> int echo_keys = 0;
> @@ -103,3 +107,16 @@ guestfs_int_mllib_set_keys_from_stdin (value unitv)
> keys_from_stdin = 1;
> return Val_unit;
> }
> +
> +value
> +guestfs_int_mllib_open_out_channel_from_fd (value fdv)
> +{
> + CAMLparam1 (fdv);
> + struct channel *chan;
> +
> + chan = caml_open_descriptor_out (Int_val (fdv));
> + if (!chan)
> + caml_raise_out_of_memory ();
> +
> + CAMLreturn (caml_alloc_channel (chan));
> +}
> diff --git a/common/mltools/tools_utils.ml b/common/mltools/tools_utils.ml
> index ade4cb37f..3c54cd4a0 100644
> --- a/common/mltools/tools_utils.ml
> +++ b/common/mltools/tools_utils.ml
> @@ -32,6 +32,7 @@ and key_store_key =
> external c_inspect_decrypt : Guestfs.t -> int64 -> (string * key_store_key)
> list -> unit = "guestfs_int_mllib_inspect_decrypt"
> external c_set_echo_keys : unit -> unit = "guestfs_int_mllib_set_echo_keys"
> "noalloc"
> external c_set_keys_from_stdin : unit -> unit =
> "guestfs_int_mllib_set_keys_from_stdin" "noalloc"
> +external c_out_channel_from_fd : int -> out_channel =
> "guestfs_int_mllib_open_out_channel_from_fd"
>
> type machine_readable_fn = {
> pr : 'a. ('a, unit, string, unit) format4 -> 'a;
> @@ -41,6 +42,7 @@ type machine_readable_output_type =
> | NoOutput
> | Channel of out_channel
> | File of string
> + | Fd of int
> let machine_readable_output = ref NoOutput
> let machine_readable_channel = ref None
> let machine_readable () =
> @@ -50,7 +52,8 @@ let machine_readable () =
> match !machine_readable_output with
> | NoOutput -> None
> | Channel chan -> Some chan
> - | File f -> Some (open_out f) in
> + | File f -> Some (open_out f)
> + | Fd fd -> Some (c_out_channel_from_fd fd) in
> machine_readable_channel := chan
> );
> !machine_readable_channel
> @@ -296,6 +299,11 @@ let create_standard_options argspec ?anon_fun ?(key_opts
> = false) ?(machine_read
> | n ->
> error (f_"invalid output stream for --machine-readable: %s") fmt
> in
> machine_readable_output := Channel chan
> + | "fd" ->
> + (try
> + machine_readable_output := Fd (int_of_string outname)
> + with Failure _ ->
> + error (f_"invalid output fd for --machine-readable: %s") fmt)
> | n ->
> error (f_"invalid output for --machine-readable: %s") fmt
> )
> diff --git a/lib/guestfs.pod b/lib/guestfs.pod
> index 53cece2da..f11028466 100644
> --- a/lib/guestfs.pod
> +++ b/lib/guestfs.pod
> @@ -3287,6 +3287,11 @@ The possible values are:
>
> =over 4
>
> +=item B<fd:>I<fd>
> +
> +The output goes to the specified I<fd>, which is a file descriptor
> +already opened for writing.
> +
> =item B<file:>F<filename>
>
> The output goes to the specified F<filename>.
> --
> 2.20.1
>
> _______________________________________________
> Libguestfs mailing list
> Libguestfs@redhat.com
> https://www.redhat.com/mailman/listinfo/libguestfs
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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