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>
(cherry picked from commit e5ff5a36dd126ee57dca4e0b03da2f7704e0a4f5)
Signed-off-by: Ole Troan <ot@cisco.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/src/tools/vppapigen/vppapigen_c.py b/src/tools/vppapigen/vppapigen_c.py
index 19efc99dae0..c1bc11d4a12 100644
--- a/src/tools/vppapigen/vppapigen_c.py
+++ b/src/tools/vppapigen/vppapigen_c.py
@@ -153,8 +153,15 @@ def typedefs(objs, aliases, filename):
                     if b.lengthfield:
                         output += "    %s %s[0];\n" % (api2c(b.fieldtype), b.fieldname)
                     else:
-                        output += "    %s %s[%s];\n" % (api2c(b.fieldtype), b.fieldname,
-                                                        b.length)
+                        # Fixed length strings decay to nul terminated u8
+                        if b.fieldtype == 'string':
+                            if b.modern_vla:
+                                output += '    {} {};\n'.format(api2c(b.fieldtype), b.fieldname)
+                            else:
+                                output += '    u8 {}[{}];\n'.format(b.fieldname, b.length)
+                        else:
+                            output += "    %s %s[%s];\n" % (api2c(b.fieldtype), b.fieldname,
+                                                            b.length)
                 else:
                     raise ValueError("Error in processing array type %s" % b)