[Libguestfs] [PATCH v11 4/8] builder: add Utils.get_image_infos function

[Cédric Bosdonnat]

This helper function calls qemu-img info on an image file and
returns the output as a JSON Yajl tree.

This function will be used in future commits.
---
 builder/Makefile.am | 2 +-
 builder/utils.ml    | 6 ++++++
 builder/utils.mli   | 4 ++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/builder/Makefile.am b/builder/Makefile.am
index 4a2f639c3..88392d327 100644
--- a/builder/Makefile.am
+++ b/builder/Makefile.am
@@ -61,12 +61,12 @@ SOURCES_MLI = \
 	yajl.mli
 
 SOURCES_ML = \
+	yajl.ml \
 	utils.ml \
 	pxzcat.ml \
 	setlocale.ml \
 	index.ml \
 	ini_reader.ml \
-	yajl.ml \
 	paths.ml \
 	languages.ml \
 	cache.ml \
diff --git a/builder/utils.ml b/builder/utils.ml
index acb6c2f4b..9fceee282 100644
--- a/builder/utils.ml
+++ b/builder/utils.ml
@@ -33,3 +33,9 @@ and revision =
 let string_of_revision = function
   | Rev_int n -> string_of_int n
   | Rev_string s -> s
+
+let get_image_infos filepath =
+  let qemuimg_cmd = "qemu-img info --output json " ^ (Std_utils.quote filepath) in
+  let lines = external_command qemuimg_cmd in
+  let line = String.concat "\n" lines in
+  Yajl.yajl_tree_parse line
diff --git a/builder/utils.mli b/builder/utils.mli
index 45385f713..4acde9f36 100644
--- a/builder/utils.mli
+++ b/builder/utils.mli
@@ -28,3 +28,7 @@ and revision =
 
 val string_of_revision : revision -> string
 (** Convert a {!revision} into a string. *)
+
+val get_image_infos : string -> Yajl.yajl_val 
+(** [get_image_infos path] Run qemu-img info on the image pointed at
+    path as YAJL tree. *)
-- 
2.13.2