Added the write function

Author: liuzicheng1987

include/rfl/cbor/write.hpp

@@ -1,8 +1,9 @@
 #ifndef RFL_CBOR_WRITE_HPP_
 #define RFL_CBOR_WRITE_HPP_
 
-#include <bson/bson.h>
+#include <cbor.h>
 
+#include <cstdint>
 #include <ostream>
 #include <sstream>
 #include <string>
@@ -14,45 +15,41 @@
 namespace rfl {
 namespace cbor {
 
-/// Returns CBOR bytes. Careful: It is the responsibility of the caller to call
-/// bson_free on the returned pointer.
 template <class T>
-std::pair<uint8_t*, size_t> to_buffer(const T& _obj) noexcept {
+void write_into_buffer(const T& _obj, CborEncoder* _encoder,
+                       std::vector<char>* _buffer) noexcept {
   using ParentType = parsing::Parent<Writer>;
-  bson_t* doc = nullptr;
-  uint8_t* buf = nullptr;
-  size_t buflen = 0;
-  bson_writer_t* bson_writer =
-      bson_writer_new(&buf, &buflen, 0, bson_realloc_ctx, NULL);
-  bson_writer_begin(bson_writer, &doc);
-  const auto rfl_writer = Writer(doc);
-  Parser<T>::write(rfl_writer, _obj, typename ParentType::Root{});
-  bson_writer_end(bson_writer);
-  const auto len = bson_writer_get_length(bson_writer);
-  bson_writer_destroy(bson_writer);
-  return std::make_pair(buf, len);
+  cbor_encoder_init(_encoder, _buffer->data(), _buffer->size(), 0);
+  const auto writer = Writer(_encoder);
+  Parser<T>::write(writer, _obj, typename ParentType::Root{});
 }
 
 /// Returns CBOR bytes.
 template <class T>
 std::vector<char> write(const T& _obj) noexcept {
-  auto [buf, len] = to_buffer(_obj);
-  const auto result = std::vector<char>(reinterpret_cast<char*>(buf),
-                                        reinterpret_cast<char*>(buf) + len);
-  bson_free(buf);
-  return result;
+  std::vector<char> buffer(128);
+  CborEncoder encoder;
+  write_into_buffer(_obj, &encoder, &buffer);
+  const auto total_bytes_needed =
+      buffer.size() + cbor_encoder_get_extra_bytes_needed(&encoder);
+  if (total_bytes_needed != buffer.size()) {
+    buffer.resize(total_bytes_needed);
+    write_into_buffer(_obj, &encoder, &buffer);
+  }
+  const auto length = cbor_encoder_get_buffer_size(&encoder);
+  buffer.resize(length);
+  return buffer;
 }
 
 /// Writes a CBOR into an ostream.
 template <class T>
 std::ostream& write(const T& _obj, std::ostream& _stream) noexcept {
-  auto [buf, len] = to_buffer(_obj);
-  _stream.write(reinterpret_cast<const char*>(buf), len);
-  bson_free(buf);
+  auto buffer = write(_obj);
+  _stream.write(buffer.data(), buffer.size());
   return _stream;
 }
 
 }  // namespace cbor
 }  // namespace rfl
 
-#endif  // CBOR_PARSER_HPP_
+#endif