pw_protobuf: Start decoder class
This change adds a Decoder class to the pw_protobuf module for decoding
protobuf messages from their wire format. The decoder interface is event
based, with a user-defined handler responsible for processing each field
in the message as it is encountered.
Currently, only varint fields are supported in the decoder. The other
protobuf wire types will be added in a future change.
Change-Id: I5a16d1864bb082d0ac1ec759064c33bb27db3e72
diff --git a/pw_protobuf/decoder_test.cc b/pw_protobuf/decoder_test.cc
new file mode 100644
index 0000000..45fe93d
--- /dev/null
+++ b/pw_protobuf/decoder_test.cc
@@ -0,0 +1,217 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+#include "pw_protobuf/decoder.h"
+
+#include "gtest/gtest.h"
+#include "pw_preprocessor/util.h"
+
+namespace pw::protobuf {
+namespace {
+
+class TestDecodeHandler : public DecodeHandler {
+ public:
+ Status ProcessField(Decoder* decoder, uint32_t field_number) override {
+ switch (field_number) {
+ case 1:
+ decoder->ReadInt32(field_number, &test_int32);
+ break;
+ case 2:
+ decoder->ReadSint32(field_number, &test_sint32);
+ break;
+ }
+
+ called = true;
+ return Status::OK;
+ }
+
+ bool called = false;
+ int32_t test_int32 = 0;
+ int32_t test_sint32 = 0;
+};
+
+TEST(Decoder, Decode) {
+ Decoder decoder;
+ TestDecodeHandler handler;
+
+ // clang-format off
+ uint8_t encoded_proto[] = {
+ // type=int32, k=1, v=42
+ 0x08, 0x2a,
+ // type=sint32, k=2, v=-13
+ 0x10, 0x19,
+ // type=bool, k=3, v=false
+ 0x18, 0x00,
+ // type=double, k=4, v=3.14159
+ 0x21, 0x6e, 0x86, 0x1b, 0xf0, 0xf9, 0x21, 0x09, 0x40,
+ // type=fixed32, k=5, v=0xdeadbeef
+ 0x2d, 0xef, 0xbe, 0xad, 0xde,
+ };
+ // clang-format on
+
+ decoder.set_handler(&handler);
+ EXPECT_EQ(decoder.Decode(as_bytes(span(encoded_proto))), Status::OK);
+ EXPECT_TRUE(handler.called);
+ EXPECT_EQ(handler.test_int32, 42);
+ EXPECT_EQ(handler.test_sint32, -13);
+}
+
+TEST(Decoder, Decode_OverridesDuplicateFields) {
+ Decoder decoder;
+ TestDecodeHandler handler;
+
+ // clang-format off
+ uint8_t encoded_proto[] = {
+ // type=int32, k=1, v=42
+ 0x08, 0x2a,
+ // type=int32, k=1, v=43
+ 0x08, 0x2b,
+ // type=int32, k=1, v=44
+ 0x08, 0x2c,
+ };
+ // clang-format on
+
+ decoder.set_handler(&handler);
+ EXPECT_EQ(decoder.Decode(as_bytes(span(encoded_proto))), Status::OK);
+ EXPECT_TRUE(handler.called);
+ EXPECT_EQ(handler.test_int32, 44);
+}
+
+TEST(Decoder, Decode_Empty) {
+ Decoder decoder;
+ TestDecodeHandler handler;
+
+ decoder.set_handler(&handler);
+ EXPECT_EQ(decoder.Decode(span<std::byte>()), Status::OK);
+ EXPECT_FALSE(handler.called);
+ EXPECT_EQ(handler.test_int32, 0);
+ EXPECT_EQ(handler.test_sint32, 0);
+}
+
+TEST(Decoder, Decode_BadData) {
+ Decoder decoder;
+ TestDecodeHandler handler;
+
+ // Field key without a value.
+ uint8_t encoded_proto[] = {0x08};
+
+ decoder.set_handler(&handler);
+ EXPECT_EQ(decoder.Decode(as_bytes(span(encoded_proto))), Status::DATA_LOSS);
+}
+
+// Only processes fields numbered 1 or 3.
+class OneThreeDecodeHandler : public DecodeHandler {
+ public:
+ Status ProcessField(Decoder* decoder, uint32_t field_number) override {
+ switch (field_number) {
+ case 1:
+ EXPECT_EQ(decoder->ReadInt32(field_number, &field_one), Status::OK);
+ break;
+ case 3:
+ EXPECT_EQ(decoder->ReadInt32(field_number, &field_three), Status::OK);
+ break;
+ default:
+ // Do nothing.
+ break;
+ }
+
+ called = true;
+ return Status::OK;
+ }
+
+ bool called = false;
+ int32_t field_one = 0;
+ int32_t field_three = 0;
+};
+
+TEST(Decoder, Decode_SkipsUnprocessedFields) {
+ Decoder decoder;
+ OneThreeDecodeHandler handler;
+
+ // clang-format off
+ uint8_t encoded_proto[] = {
+ // type=int32, k=1, v=42
+ // Should be read.
+ 0x08, 0x2a,
+ // type=sint32, k=2, v=-13
+ // Should be ignored.
+ 0x10, 0x19,
+ // type=int32, k=2, v=3
+ // Should be ignored.
+ 0x10, 0x03,
+ // type=int32, k=3, v=99
+ // Should be read.
+ 0x18, 0x63,
+ // type=int32, k=4, v=16
+ // Should be ignored.
+ 0x20, 0x10,
+ };
+ // clang-format on
+
+ decoder.set_handler(&handler);
+ EXPECT_EQ(decoder.Decode(as_bytes(span(encoded_proto))), Status::OK);
+ EXPECT_TRUE(handler.called);
+ EXPECT_EQ(handler.field_one, 42);
+ EXPECT_EQ(handler.field_three, 99);
+}
+
+// Only processes fields numbered 1 or 3.
+class ExitOnOneDecoder : public DecodeHandler {
+ public:
+ Status ProcessField(Decoder* decoder, uint32_t field_number) override {
+ switch (field_number) {
+ case 1:
+ EXPECT_EQ(decoder->ReadInt32(field_number, &field_one), Status::OK);
+ return Status::CANCELLED;
+ case 3:
+ EXPECT_EQ(decoder->ReadInt32(field_number, &field_three), Status::OK);
+ break;
+ default:
+ // Do nothing.
+ break;
+ }
+
+ return Status::OK;
+ }
+
+ int32_t field_one = 0;
+ int32_t field_three = 1111;
+};
+
+TEST(Decoder, Decode_StopsOnNonOkStatus) {
+ Decoder decoder;
+ ExitOnOneDecoder handler;
+
+ // clang-format off
+ uint8_t encoded_proto[] = {
+ // type=int32, k=1, v=42
+ // Should be read.
+ 0x08, 0x2a,
+ // type=int32, k=3, v=99
+ // Should be skipped.
+ 0x18, 0x63,
+ // type=int32, k=2, v=16
+ // Should be skipped.
+ 0x08, 0x10,
+ };
+ // clang-format on
+
+ decoder.set_handler(&handler);
+ EXPECT_EQ(decoder.Decode(as_bytes(span(encoded_proto))), Status::CANCELLED);
+ EXPECT_EQ(handler.field_one, 42);
+ EXPECT_EQ(handler.field_three, 1111);
+}
+
+} // namespace
+} // namespace pw::protobuf