varlink,json: introduce new varlink_dispatch() helper

varlink_dispatch() is a simple wrapper around json_dispatch() that
returns clean, standards-compliant InvalidParameter error back to
clients, if the specified JSON cannot be parsed properly.

For this json_dispatch() is extended to return the offending field's
name. Because it already has quite a few parameters, I then renamed
json_dispatch() to json_dispatch_full() and made json_dispatch() a
wrapper around it that passes the new argument as NULL. While doing so I
figured we should also get rid of the bad= argument in the short
wrapper, since it's only used in the OCI code.

To simplify the OCI code this adds a second wrapper oci_dispatch()
around json_dispatch_full(), that fills in bad= the way we want.

Net result: instead of one json_dispatch() call there are now:

1. json_dispatch_full() for the fully feature mother of all dispathers.
2. json_dispatch() for the simpler version that you want to use most of
   the time.
3. varlink_dispatch() that generates nice Varlink errors
4. oci_dispatch() that does the OCI specific error handling

And that's all there is.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/shared/varlink.h b/src/shared/varlink.h
index 516d3b5a90..6ec708aba2 100644
--- a/src/shared/varlink.h
+++ b/src/shared/varlink.h
@@ -115,6 +115,9 @@ int varlink_error_errno(Varlink *v, int error);
 int varlink_notify(Varlink *v, JsonVariant *parameters);
 int varlink_notifyb(Varlink *v, ...);
 
+/* Parsing incoming data via json_dispatch() and generate a nice error on parse errors */
+int varlink_dispatch(Varlink *v, JsonVariant *parameters, const JsonDispatch table[], void *userdata);
+
 /* Write outgoing fds into the socket (to be associated with the next enqueued message) */
 int varlink_push_fd(Varlink *v, int fd);
 int varlink_dup_fd(Varlink *v, int fd);