api: enforce vla is last and fixed string type

Enforce that variable length fields are the last element of API messages.

Add a 'fixed' version of string type, since dealing with
multiple variable length strings turned out too painful
for the C language bindings.

The string type is now:
{
  string name[64]; // NUL terminated C-string. Essentially decays to u8 name[64]
  string name[];   // Variable length string with embedded len field (vl_api_string_t)
};

The latter notation could be made available to other types as well.
e.g.
{
  vl_api_address_t addresses[];
}
instead of

{
  u32 n_addr;
  vl_api_address_t addresses[n_addr];
};

Type: fix
Change-Id: I18fa17ef47227633752ab50453e8d20a652a9f9b
Signed-off-by: Ole Troan <ot@cisco.com>

2 files changed, 13 insertions, 4 deletions

diff --git a/src/vpp-api/vapi/vapi_c_gen.py b/src/vpp-api/vapi/vapi_c_gen.py
index 381dcba7f42..b9b9aa750a8 100755
--- a/src/vpp-api/vapi/vapi_c_gen.py
+++ b/src/vpp-api/vapi/vapi_c_gen.py
@@ -13,10 +13,16 @@ class CField(Field):
         return "vapi_type_%s" % self.name
 
     def get_c_def(self):
-        if self.len is not None:
-            return "%s %s[%d];" % (self.type.get_c_name(), self.name, self.len)
+        if self.type.get_c_name() == 'vl_api_string_t':
+            if self.len:
+                return "u8 %s[%d];" % (self.name, self.len)
+            else:
+                return "vl_api_string_t %s;" % (self.name)
         else:
-            return "%s %s;" % (self.type.get_c_name(), self.name)
+            if self.len is not None:
+                return "%s %s[%d];" % (self.type.get_c_name(), self.name, self.len)
+            else:
+                return "%s %s;" % (self.type.get_c_name(), self.name)
 
     def get_swap_to_be_code(self, struct, var):
         if self.len is not None:
diff --git a/src/vpp-api/vapi/vapi_json_parser.py b/src/vpp-api/vapi/vapi_json_parser.py
index a9d2c8186bc..d7669365ce8 100644
--- a/src/vpp-api/vapi/vapi_json_parser.py
+++ b/src/vpp-api/vapi/vapi_json_parser.py
@@ -177,12 +177,15 @@ class Message(object):
                     p = field_class(field_name=field[1],
                                     field_type=field_type)
                 elif l == 3:
-                    if field[2] == 0:
+                    if field[2] == 0 and field[0] != 'string':
                         raise ParseError(
                             "While parsing message `%s': variable length "
                             "array `%s' doesn't have reference to member "
                             "containing the actual length" % (
                                 name, field[1]))
+                    if field[0] == 'string' and field[2] > 0:
+                        field_type = json_parser.lookup_type_like_id('u8')
+
                     p = field_class(
                         field_name=field[1],
                         field_type=field_type,