[PATCH RFC 2/9] libxl_json: introduce libx__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>
---
 tools/libxl/libxl_internal.h |    9 +++++++++
 tools/libxl/libxl_json.c     |   34 ++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+)

diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index b3a200d..34b6a26 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1494,6 +1494,15 @@ typedef yajl_gen_status (*libxl__gen_json_callback)(yajl_gen hand, void *);
 _hidden char *libxl__object_to_json(libxl_ctx *ctx, const char *type,
                                     libxl__gen_json_callback gen, void *p);
 
+typedef struct libxl__json_object libxl__json_object;
+typedef int (*libxl__parse_json_callback)(libxl_ctx *ctx,
+                                          libxl__json_object *o,
+                                          void *p);
+_hidden int libxl__object_from_json(libxl_ctx *ctx, const char *type,
+                                    libxl__parse_json_callback parse,
+                                    void *p,
+                                    const char *s);
+
   /* holds the CPUID response for a single CPUID leaf
    * input contains the value of the EAX and ECX register,
    * and each policy string contains a filter to apply to
diff --git a/tools/libxl/libxl_json.c b/tools/libxl/libxl_json.c
index 3ea56a4..002ae2d 100644
--- a/tools/libxl/libxl_json.c
+++ b/tools/libxl/libxl_json.c
@@ -794,6 +794,40 @@ out:
     return ret;
 }
 
+int libxl__object_from_json(libxl_ctx *ctx, const char *type,
+                            libxl__parse_json_callback parse,
+                            void *p, const char *s)
+{
+    GC_INIT(ctx);
+    libxl__json_object *o = NULL;
+    int ret;
+
+    o = libxl__json_parse(gc, s);
+
+    if (!o) {
+        LIBXL__LOG(ctx, LIBXL__LOG_ERROR,
+                   "unable to generate libxl__json_object from JSON representation for %s.",
+                   type);
+        ret = -1;
+        goto out;
+    }
+
+    ret = parse(ctx, o, p);
+
+    if (ret) {
+        LIBXL__LOG(ctx, LIBXL__LOG_ERROR,
+                   "unable to convert libxl__json_object to %s.",
+                   type);
+        ret = -1;
+        goto out;
+    }
+
+    ret = 0;
+out:
+    GC_FREE;
+    return ret;
+}
+
 /*
  * Local variables:
  * mode: C
-- 
1.7.10.4