build-aux: Generate ofp field decoders.

Based on meta-field information extracted by extract_ofp_fields,
autogenerate the right decoder to be used.

Acked-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Adrian Moreno <amorenoz@redhat.com>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

build-aux/automake.mk

@@ -5,6 +5,7 @@ EXTRA_DIST += \
 	build-aux/dist-docs \
 	build-aux/dpdkstrip.py \
 	build-aux/generate-dhparams-c \
+	build-aux/gen_ofp_field_decoders \
 	build-aux/initial-tab-allowed-files \
 	build-aux/sodepends.py \
 	build-aux/soexpand.py \
@@ -12,7 +13,8 @@ EXTRA_DIST += \
 	build-aux/xml2nroff
 
 FLAKE8_PYFILES += \
-    $(srcdir)/build-aux/xml2nroff \
     build-aux/dpdkstrip.py \
+    build-aux/gen_ofp_field_decoders \
     build-aux/sodepends.py \
-    build-aux/soexpand.py
+    build-aux/soexpand.py \
+    build-aux/xml2nroff

build-aux/gen_ofp_field_decoders

@@ -0,0 +1,67 @@
+#!/bin/env python
+
+import argparse
+
+import build.extract_ofp_fields as extract_fields
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Tool to generate python ofproto field decoders from"
+        "meta-flow information"
+    )
+    parser.add_argument(
+        "metaflow",
+        metavar="FILE",
+        type=str,
+        help="Read meta-flow info from file",
+    )
+
+    args = parser.parse_args()
+
+    fields = extract_fields.extract_ofp_fields(args.metaflow)
+
+    field_decoders = {}
+    for field in fields:
+        decoder = get_decoder(field)
+        field_decoders[field.get("name")] = decoder
+        if field.get("extra_name"):
+            field_decoders[field.get("extra_name")] = decoder
+
+    code = """
+# This file is auto-generated. Do not edit!
+
+from ovs.flow import decoders
+
+field_decoders = {{
+{decoders}
+}}""".format(
+        decoders="\n".join(
+            [
+                "    '{name}': {decoder},".format(name=name, decoder=decoder)
+                for name, decoder in field_decoders.items()
+            ]
+        )
+    )
+    print(code)
+
+
+def get_decoder(field):
+    formatting = field.get("formatting")
+    if formatting in ["decimal", "hexadecimal"]:
+        if field.get("mask") == "MFM_NONE":
+            return "decoders.decode_int"
+        else:
+            if field.get("n_bits") in [8, 16, 32, 64, 128, 992]:
+                return "decoders.Mask{}".format(field.get("n_bits"))
+            return "decoders.decode_mask({})".format(field.get("n_bits"))
+    elif formatting in ["IPv4", "IPv6"]:
+        return "decoders.IPMask"
+    elif formatting == "Ethernet":
+        return "decoders.EthMask"
+    else:
+        return "decoders.decode_default"
+
+
+if __name__ == "__main__":
+    main()

python/automake.mk

@@ -30,6 +30,7 @@ ovs_pyfiles = \
 	python/ovs/flow/decoders.py \
 	python/ovs/flow/kv.py \
 	python/ovs/flow/list.py \
+	python/ovs/flow/ofp_fields.py \
 	python/ovs/json.py \
 	python/ovs/jsonrpc.py \
 	python/ovs/ovsuuid.py \
@@ -127,3 +128,9 @@ EXTRA_DIST += python/ovs/dirs.py.template
 CLEANFILES += python/ovs/dirs.py
 
 EXTRA_DIST += python/TODO.rst
+
+$(srcdir)/python/ovs/flow/ofp_fields.py: $(srcdir)/build-aux/gen_ofp_field_decoders include/openvswitch/meta-flow.h
+	$(AM_V_GEN)$(run_python) $< $(srcdir)/include/openvswitch/meta-flow.h > $@.tmp
+	$(AM_V_at)mv $@.tmp $@
+EXTRA_DIST += python/ovs/flow/ofp_fields.py
+CLEANFILES += python/ovs/flow/ofp_fields.py

python/ovs/.gitignore

@@ -1,2 +1,3 @@
-version.py
 dirs.py
+flow/ofp_fields.py
+version.py