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Re: [Libguestfs] [PATCH v11 7/8] mllib: add XPath helper xpath_get_nodes



On Fri, Oct 27, 2017 at 04:08:21PM +0200, Cédric Bosdonnat wrote:
> This function will allow more OCaml-ish processing of XPath queries
> with multiple results.
> ---
>  common/mltools/xpath_helpers.ml      |  9 +++++++
>  common/mltools/xpath_helpers.mli     |  4 +++
>  v2v/output_libvirt.ml                | 11 ++------
>  v2v/test-harness/v2v_test_harness.ml | 51 +++++++++++-------------------------
>  4 files changed, 30 insertions(+), 45 deletions(-)
> 
> diff --git a/common/mltools/xpath_helpers.ml b/common/mltools/xpath_helpers.ml
> index 3afee8b21..d2bfd3fb9 100644
> --- a/common/mltools/xpath_helpers.ml
> +++ b/common/mltools/xpath_helpers.ml
> @@ -40,3 +40,12 @@ let xpath_eval parsefn xpathctx expr =
>  let xpath_string = xpath_eval identity
>  let xpath_int = xpath_eval int_of_string
>  let xpath_int64 = xpath_eval Int64.of_string
> +
> +let xpath_get_nodes xpathctx expr =
> +  let obj = Xml.xpath_eval_expression xpathctx expr in
> +  let nodes = ref [] in
> +  for i = 0 to Xml.xpathobj_nr_nodes obj - 1 do
> +    let node = Xml.xpathobj_node obj i in
> +    push_front node nodes
> +  done;
> +  List.rev !nodes
> diff --git a/common/mltools/xpath_helpers.mli b/common/mltools/xpath_helpers.mli
> index 3a8190b05..3a2607aeb 100644
> --- a/common/mltools/xpath_helpers.mli
> +++ b/common/mltools/xpath_helpers.mli
> @@ -25,3 +25,7 @@ val xpath_int : Xml.xpathctx -> string -> int option
>  val xpath_int64 : Xml.xpathctx -> string -> int64 option
>  (** Parse an xpath expression and return a string/int.  Returns
>      [Some v], or [None] if the expression doesn't match. *)
> +
> +val xpath_get_nodes : Xml.xpathctx -> string -> Xml.node list
> +(** Parse an XPath expression and return a list with the matching
> +    XML nodes. *)
> diff --git a/v2v/output_libvirt.ml b/v2v/output_libvirt.ml
> index 02b4d54ff..729f8b67a 100644
> --- a/v2v/output_libvirt.ml
> +++ b/v2v/output_libvirt.ml
> @@ -55,15 +55,8 @@ let target_features_of_capabilities_doc doc arch =
>      Xml.xpathctx_set_current_context xpathctx node;
>  
>      (* Get guest/features/* nodes. *)
> -    let obj = Xml.xpath_eval_expression xpathctx "features/*" in
> -
> -    let features = ref [] in
> -    for i = 0 to Xml.xpathobj_nr_nodes obj - 1 do
> -      let feature_node = Xml.xpathobj_node obj i in
> -      let feature_name = Xml.node_name feature_node in
> -      push_front feature_name features
> -    done;
> -    !features
> +    let features = xpath_get_nodes xpathctx "features/*" in
> +    List.map Xml.node_name features
>    )
>  
>  class output_libvirt oc output_pool = object
> diff --git a/v2v/test-harness/v2v_test_harness.ml b/v2v/test-harness/v2v_test_harness.ml
> index ae0033dde..79e97a4b2 100644
> --- a/v2v/test-harness/v2v_test_harness.ml
> +++ b/v2v/test-harness/v2v_test_harness.ml
> @@ -25,6 +25,7 @@ open Printf
>  
>  open Std_utils
>  open Tools_utils
> +open Xpath_helpers
>  
>  type test_plan = {
>    guest_clock : float option;
> @@ -90,29 +91,18 @@ let run ~test ?input_disk ?input_xml ?(test_plan = default_plan) () =
>      g, root
>    in
>  
> -  let nodes_of_xpathobj doc xpathobj =
> -    let nodes = ref [] in
> -    for i = 0 to Xml.xpathobj_nr_nodes xpathobj - 1 do
> -      push_front (Xml.xpathobj_node xpathobj i) nodes
> -    done;
> -    List.rev !nodes
> -  in
> -
>    let test_boot boot_disk boot_xml_doc =
>      (* Modify boot XML (in memory). *)
>      let xpathctx = Xml.xpath_new_context boot_xml_doc in
>  
>      (* Change <name> to something unique. *)
>      let domname = "tmpv2v-" ^ test in
> -    let xpath = Xml.xpath_eval_expression xpathctx "/domain/name" in
> -    let nodes = nodes_of_xpathobj boot_xml_doc xpath in
> +    let nodes = xpath_get_nodes xpathctx "/domain/name" in
>      List.iter (fun node -> Xml.node_set_content node domname) nodes;
>  
>      (* Limit the RAM used by the guest to 2GB. *)
> -    let xpath = Xml.xpath_eval_expression xpathctx "/domain/memory" in
> -    let nodes = nodes_of_xpathobj boot_xml_doc xpath in
> -    let xpath = Xml.xpath_eval_expression xpathctx "/domain/currentMemory" in
> -    let nodes = nodes @ nodes_of_xpathobj boot_xml_doc xpath in
> +    let nodes = xpath_get_nodes xpathctx "/domain/memory" in
> +    let nodes = nodes @ xpath_get_nodes xpathctx "/domain/currentMemory" in
>      List.iter (
>        fun node ->
>          let i = int_of_string (Xml.node_as_string node) in
> @@ -127,8 +117,7 @@ let run ~test ?input_disk ?input_xml ?(test_plan = default_plan) () =
>          let adjustment = t -. time () in
>          assert (adjustment <= 0.);
>          let adjustment = int_of_float adjustment in
> -        let xpath = Xml.xpath_eval_expression xpathctx "/domain/clock" in
> -        let nodes = nodes_of_xpathobj boot_xml_doc xpath in
> +        let nodes = xpath_get_nodes xpathctx "/domain/clock" in
>          let clock_node =
>            match nodes with
>            | [] ->
> @@ -147,8 +136,7 @@ let run ~test ?input_disk ?input_xml ?(test_plan = default_plan) () =
>      );
>  
>      (* Remove all devices except for a whitelist. *)
> -    let xpath = Xml.xpath_eval_expression xpathctx "/domain/devices/*" in
> -    let nodes = nodes_of_xpathobj boot_xml_doc xpath in
> +    let nodes = xpath_get_nodes xpathctx "/domain/devices/*" in
>      List.iter (
>        fun node ->
>          match Xml.node_name node with
> @@ -157,33 +145,26 @@ let run ~test ?input_disk ?input_xml ?(test_plan = default_plan) () =
>      ) nodes;
>  
>      (* Remove CDROMs. *)
> -    let xpath =
> -      Xml.xpath_eval_expression xpathctx
> -        "/domain/devices/disk[ device=\"cdrom\"]" in
> -    let nodes = nodes_of_xpathobj boot_xml_doc xpath in
> +    let nodes = xpath_get_nodes xpathctx
> +      "/domain/devices/disk[ device=\"cdrom\"]" in
>      List.iter Xml.unlink_node nodes;
>  
>      (* Change <on_*> settings to destroy ... *)
> -    let xpath = Xml.xpath_eval_expression xpathctx "/domain/on_poweroff" in
> -    let nodes = nodes_of_xpathobj boot_xml_doc xpath in
> -    let xpath = Xml.xpath_eval_expression xpathctx "/domain/on_crash" in
> -    let nodes = nodes @ nodes_of_xpathobj boot_xml_doc xpath in
> +    let nodes = xpath_get_nodes xpathctx "/domain/on_poweroff" in
> +    let nodes = nodes @ xpath_get_nodes xpathctx "/domain/on_crash" in
>      List.iter (fun node -> Xml.node_set_content node "destroy") nodes;
>      (* ... except for <on_reboot> which is permitted (for SELinux
>       * relabelling)
>       *)
> -    let xpath = Xml.xpath_eval_expression xpathctx "/domain/on_reboot" in
> -    let nodes = nodes_of_xpathobj boot_xml_doc xpath in
> +    let nodes = xpath_get_nodes xpathctx "/domain/on_reboot" in
>      List.iter (fun node -> Xml.node_set_content node "restart") nodes;
>  
>      (* Get the name of the disk device (eg. "sda"), which is used
>       * for getting disk stats.
>       *)
> -    let xpath =
> -      Xml.xpath_eval_expression xpathctx
> -        "/domain/devices/disk[ device=\"disk\"]/target/@dev" in
>      let dev =
> -      match nodes_of_xpathobj boot_xml_doc xpath with
> +      match xpath_get_nodes xpathctx
> +        "/domain/devices/disk[ device=\"disk\"]/target/@dev" with
>        | [node] -> Xml.node_as_string node
>        | _ -> assert false in
>  
> @@ -523,10 +504,8 @@ let run ~test ?input_disk ?input_xml ?(test_plan = default_plan) () =
>      (* We need to remember to change the XML to point to the boot overlay. *)
>      let () =
>        let xpathctx = Xml.xpath_new_context boot_xml_doc in
> -      let xpath =
> -        Xml.xpath_eval_expression xpathctx
> -          "/domain/devices/disk[ device=\"disk\"]/source" in
> -      match nodes_of_xpathobj boot_xml_doc xpath with
> +      match xpath_get_nodes xpathctx
> +        "/domain/devices/disk[ device=\"disk\"]/source" with
>        | [node] ->
>          (* Libvirt requires that the path is absolute. *)
>          let abs_boot_disk = Sys.getcwd () // boot_disk in

ACK

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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