wrap-json: Update the documentation

Signed-off-by: jobol <jose.bollo@iot.bzh>

1 files changed, 13 insertions, 0 deletions

diff --git a/wrap-json.md b/wrap-json.md
index a86d2a5..8f7693c 100644
--- a/wrap-json.md
+++ b/wrap-json.md
@@ -75,6 +75,19 @@ arguments.
 
 :   Like 'y' but output is base64.
 
+`y?`, `Y?` (byte array or null) \[const uint8_t \*, size\_t\]
+
+:   Like 'y' or 'Y' but allows to output a JSON null value
+    either when the buffer is *NULL* or when the size is *0*.
+
+`y*`, `y*` (optional byte array) \[const uint8_t \*, size\_t\]
+
+:   Like 'y' or 'Y' but do not put JSON value
+    either when the buffer is *NULL* or when the size is *0*.
+    This format can only be used inside an object or an array. If used
+    inside an object, the corresponding key is additionally suppressed
+    when the value is omitted. See below for an example.
+
 `n` (null)
 
 :   Output a JSON null value. No argument is consumed.