msgpack.h

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/*
 * Copyright 2026 The A11 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
 *
 *     http://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.
 */
 
#ifndef A11_DATA_MSGPACK_H_
#define A11_DATA_MSGPACK_H_
 
#include <cstddef>
#include <cstdint>
#include <string>
#include <string_view>
 
#include <absl/base/nullability.h>
#include <absl/functional/function_ref.h>
#include <absl/status/status.h>
#include <absl/status/statusor.h>
#include <nlohmann/json.hpp>
 
namespace a11::data {
 
class MsgpackWriter {
 public:
  MsgpackWriter() : bytes_(&owned_) {}
 
  explicit MsgpackWriter(std::string* absl_nonnull target) : bytes_(target) {}
 
  // Copying or moving would invalidate bytes_ when it points to owned_.
  MsgpackWriter(const MsgpackWriter&) = delete;
  MsgpackWriter& operator=(const MsgpackWriter&) = delete;
 
  absl::Status Pack(const nlohmann::json& value);
 
  // Typed field writers encode directly into the buffer and match Pack()'s
  // MessagePack representation. MsgpackWriterEncodingTest pins equivalence.
 
  void PackNil();
  void PackBool(bool value);
  void PackUint(std::uint64_t value);
  void PackInt(std::int64_t value);
  void PackString(std::string_view value);
  void PackBinary(std::string_view value);
  void PackArrayHeader(size_t length);
  void PackMapHeader(size_t length);
 
  absl::Status PackRecord(
      absl::FunctionRef<absl::Status(MsgpackWriter* absl_nonnull)> encode);
 
  [[nodiscard]] const std::string& bytes() const { return *bytes_; }
 
  [[nodiscard]] std::string TakeBytes() { return std::move(*bytes_); }
 
 private:
  void Reserve(size_t extra);
 
  std::string owned_;
  std::string* absl_nonnull bytes_;
};
 
class MsgpackReader {
 public:
  explicit MsgpackReader(std::string_view bytes) : bytes_(bytes) {}
 
  absl::StatusOr<nlohmann::json> Read();
 
  absl::StatusOr<std::string_view> ReadBinaryView();
 
  absl::StatusOr<size_t> ReadArrayLength();
  absl::Status EnsureFullyConsumed() const;
 
  [[nodiscard]] size_t position() const { return position_; }
 
 private:
  std::string_view bytes_;
  size_t position_ = 0;
};
 
absl::StatusOr<std::string> PackStatus(const absl::Status& status);
absl::StatusOr<absl::Status> UnpackStatus(std::string_view bytes);
 
nlohmann::json Binary(std::string_view bytes);
absl::StatusOr<std::string> GetBinary(const nlohmann::json& value,
                                      std::string_view field_name);
 
}  // namespace a11::data
 
#endif  // A11_DATA_MSGPACK_H_