[Tools] Add DGO packer and unpacker (#219)

* add dgo tools

* make codacy happy

common/util/DgoReader.cpp

@@ -0,0 +1,54 @@
+#include <cstring>
+#include <utility>
+#include <unordered_set>
+#include "DgoReader.h"
+#include "BinaryReader.h"
+#include "common/link_types.h"
+#include "third-party/json.hpp"
+#include "dgo_util.h"
+
+DgoReader::DgoReader(std::string file_name, const std::vector<u8>& data)
+    : m_file_name(std::move(file_name)) {
+  BinaryReader reader(data);
+  auto header = reader.read<DgoHeader>();
+  m_internal_name = header.name;
+  std::unordered_set<std::string> all_unique_names;
+
+  // get all obj files...
+  for (uint32_t i = 0; i < header.object_count; i++) {
+    auto obj_header = reader.read<ObjectHeader>();
+    assert(reader.bytes_left() >= obj_header.size);
+    assert_string_empty_after(obj_header.name, 60);
+
+    DgoDataEntry entry;
+    entry.internal_name = obj_header.name;
+    entry.unique_name = get_object_file_name(entry.internal_name, reader.here(), obj_header.size);
+    all_unique_names.insert(entry.unique_name);
+    entry.data.resize(obj_header.size);
+
+    assert((reader.get_seek() % 16) == 0);
+    memcpy(entry.data.data(), reader.here(), obj_header.size);
+    m_entries.push_back(entry);
+
+    reader.ffwd(obj_header.size);
+  }
+
+  // check we're at the end
+  assert(0 == reader.bytes_left());
+  assert(all_unique_names.size() == m_entries.size());
+}
+
+std::string DgoReader::description_as_json() const {
+  using namespace nlohmann;
+  json j;
+  j["file_name"] = m_file_name;
+  j["internal_name"] = m_internal_name;
+  for (auto& entry : m_entries) {
+    json entry_desc;
+    entry_desc["unique_name"] = entry.unique_name;
+    entry_desc["internal_name"] = entry.internal_name;
+    j["objects"].push_back(entry_desc);
+  }
+
+  return j.dump(4);
+}