add flatbuffers reflection support

.gitignore

@@ -1 +1,2 @@
+/.vscode/
 /bazel-*

util/BUILD

@@ -33,6 +33,25 @@ cc_test(
     ],
 )
 
+cc_library(
+    name = "flatbuffers-reflection",
+    srcs = ["flatbuffers-reflection.cc"],
+    hdrs = ["flatbuffers-reflection.h"],
+    deps = [
+        "@com_github_google_flatbuffers//:flatbuffers",
+        "@com_google_absl//absl/types:span",
+    ],
+)
+
+cc_test(
+    name = "flatbuffers-reflection_test",
+    srcs = ["flatbuffers-reflection_test.cc"],
+    deps = [
+        ":flatbuffers-reflection",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_library(
     name = "utf",
     srcs = ["utf.cc"],

util/fibonacci-sequence_test.cc

@@ -5,7 +5,7 @@
 namespace util {
 namespace {
 
-TEST(FibonacciSequenceTest, Values) {
+TEST(FibonacciSequenceTest, values) {
     FibonacciSequence<int> fib;
     EXPECT_EQ(fib.a(), 1);
     fib.next();

util/flatbuffers-reflection.cc

@@ -0,0 +1,34 @@
+#include "util/flatbuffers-reflection.h"
+
+#include "flatbuffers/reflection.h"
+
+namespace util {
+
+bool pack(
+    flatbuffers::Parser &parser,
+    const char *in,
+    std::vector<uint8_t> &out) {
+    if (!parser.Parse(in)) {
+        return false;
+    }
+    out.assign(
+        parser.builder_.GetBufferPointer(),
+        parser.builder_.GetBufferPointer() + parser.builder_.GetSize());
+    return true;
+}
+
+bool verify_and_unpack(
+    flatbuffers::Parser &parser,
+    absl::Span<const uint8_t> in,
+    std::string &out) {
+    parser.Serialize();
+    const reflection::Schema *schema = reflection::GetSchema(
+        parser.builder_.GetBufferPointer());
+    if (!flatbuffers::Verify(
+        *schema, *schema->root_table(), in.data(), in.size())) {
+        return false;
+    }
+    return flatbuffers::GenerateText(parser, in.data(), &out);
+}
+
+}  // namespace util

util/flatbuffers-reflection.h

@@ -0,0 +1,23 @@
+#ifndef _UTIL_FLATBUFFERS_REFLECTION_H
+#define _UTIL_FLATBUFFERS_REFLECTION_H
+
+#include <cstdint>
+#include <vector>
+#include "absl/types/span.h"
+#include "flatbuffers/idl.h"
+
+namespace util {
+
+bool pack(
+    flatbuffers::Parser &parser,
+    const char *in,
+    std::vector<uint8_t> &out);
+
+bool verify_and_unpack(
+    flatbuffers::Parser &parser,
+    absl::Span<const uint8_t> in,
+    std::string &out);
+
+}  // namespace util
+
+#endif  // _UTIL_FLATBUFFERS_REFLECTION_H

util/flatbuffers-reflection_test.cc

@@ -0,0 +1,21 @@
+#include "util/flatbuffers-reflection.h"
+
+#include <gtest/gtest.h>
+#include "flatbuffers/idl.h"
+
+namespace util {
+namespace {
+
+TEST(FlatbuffersReflectionDynamicTest, pack_verify_unpack) {
+    flatbuffers::Parser parser;
+    ASSERT_TRUE(parser.Parse("table TestTable { dummy: int32; }"));
+    ASSERT_TRUE(parser.SetRootType("TestTable"));
+    std::vector<uint8_t> buffer;
+    ASSERT_TRUE(pack(parser, "{dummy: 123}", buffer));
+    std::string json;
+    ASSERT_TRUE(verify_and_unpack(parser, buffer, json));
+    EXPECT_EQ(json, "{\n  dummy: 123\n}\n");
+}
+
+}  // namespace
+}  // namespace util