[PATCH V5 12/32] libxl_json: introduce libxl__object_from_json

[Wei Liu <wei.liu2@citrix.com>]

Given a JSON string, we need to convert it to libxl_FOO struct.

The approach is:
JSON string -> libxl__json_object -> libxl_FOO struct

With this approach we can make use of libxl's infrastructure to do the
first half (JSON string -> libxl__json_object).

Second half is done by auto-generated code by libxl's IDL
infrastructure. IDL patch(es) will come later.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
---
 tools/libxl/libxl_internal.h |    8 ++++++++
 tools/libxl/libxl_json.c     |   30 ++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 294c595..b2111a0 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1640,6 +1640,14 @@ typedef struct libxl__json_object {
     struct libxl__json_object *parent;
 } libxl__json_object;
 
+typedef int (*libxl__json_parse_callback)(libxl__gc *gc,
+                                          libxl__json_object *o,
+                                          void *p);
+_hidden int libxl__object_from_json(libxl_ctx *ctx, const char *type,
+                                    libxl__json_parse_callback parse,
+                                    void *p,
+                                    const char *s);
+
 typedef struct {
     char *map_key;
     libxl__json_object *obj;
diff --git a/tools/libxl/libxl_json.c b/tools/libxl/libxl_json.c
index ff23376..d2b4cfc 100644
--- a/tools/libxl/libxl_json.c
+++ b/tools/libxl/libxl_json.c
@@ -815,6 +815,36 @@ out:
     return s;
 }
 
+int libxl__object_from_json(libxl_ctx *ctx, const char *type,
+                            libxl__json_parse_callback parse,
+                            void *p, const char *s)
+{
+    GC_INIT(ctx);
+    libxl__json_object *o;
+    int rc;
+
+    o = libxl__json_parse(gc, s);
+    if (!o) {
+        LOG(ERROR,
+            "unable to generate libxl__json_object from JSON representation of %s.",
+            type);
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    rc = parse(gc, o, p);
+    if (rc) {
+        LOG(ERROR, "unable to convert libxl__json_object to %s. (rc=%d)", type, rc);
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    rc = 0;
+out:
+    GC_FREE;
+    return rc;
+}
+
 /*
  * Local variables:
  * mode: C
-- 
1.7.10.4