blobmsg: allow data/length iterator/accessor functions to work on non-blobmsg elements

This primarily helps with simplifying the ubus APIs.
blobmsg header presence is indicated by the BLOB_ATTR_EXTENDED bit in
the id_len field.

This changes the format ABI, but not the API.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/blobmsg.h b/blobmsg.h
index 4619643..e9e0e6e 100644
--- a/blobmsg.h
+++ b/blobmsg.h
@@ -65,7 +65,12 @@ static inline int blobmsg_type(const struct blob_attr *attr)
 static inline void *blobmsg_data(const struct blob_attr *attr)
 {
 	struct blobmsg_hdr *hdr = (struct blobmsg_hdr *) blob_data(attr);
-	return (char *) hdr + blobmsg_hdrlen(be16_to_cpu(hdr->namelen));
+	char *data = blob_data(attr);
+
+	if (blob_is_extended(attr))
+		data += blobmsg_hdrlen(be16_to_cpu(hdr->namelen));
+
+	return data;
 }
 
 static inline int blobmsg_data_len(const struct blob_attr *attr)