qapi: Improve qobject visitor documentation

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <1488544368-30622-29-git-send-email-armbru@redhat.com>

1 files changed, 31 insertions, 4 deletions

diff --git a/include/qapi/qobject-output-visitor.h b/include/qapi/qobject-output-visitor.h
index 8241877bd7..9b990c318e 100644
--- a/include/qapi/qobject-output-visitor.h
+++ b/include/qapi/qobject-output-visitor.h
@@ -19,11 +19,38 @@
 
 typedef struct QObjectOutputVisitor QObjectOutputVisitor;
 
-/*
- * Create a new QObject output visitor.
+/**
+ * Create a QObject output visitor for @obj
+ *
+ * A QObject output visitor visit builds a QObject from QAPI Object.
+ * This simultaneously walks the QAPI object and the QObject being
+ * built.  The latter walk starts at @obj.
+ *
+ * visit_type_FOO() creates a QObject for QAPI type FOO.  It creates a
+ * QDict for struct/union types, a QList for list types, QString for
+ * type 'str' and enumeration types, QInt for integer types, QFloat
+ * for type 'number', QBool for type 'bool'.  For type 'any', it
+ * increments the QObject's reference count.  For QAPI alternate
+ * types, it creates the QObject for the member that is in use.
+ *
+ * visit_start_struct() ... visit_end_struct() visits a QAPI
+ * struct/union and creates a QDict.  Visits in between visit the
+ * members.  visit_optional() is true when the struct/union has this
+ * member.  visit_check_struct() does nothing.
+ *
+ * visit_start_list() ... visit_end_list() visits a QAPI list and
+ * creates a QList.  Visits in between visit list members, one after
+ * the other.  visit_next_list() returns NULL when all QAPI list
+ * members have been visited.  visit_check_list() does nothing.
+ *
+ * visit_start_alternate() ... visit_end_alternate() visits a QAPI
+ * alternate.  The visit in between creates the QObject for the
+ * alternate member that is in use.
+ *
+ * Errors are not expected to happen.
  *
- * If everything else succeeds, pass @result to visit_complete() to
- * collect the result of the visit.
+ * The caller is responsible for freeing the visitor with
+ * visit_free().
  */
 Visitor *qobject_output_visitor_new(QObject **result);