standard_codec_serializer.h

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// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#ifndef FLUTTER_SHELL_PLATFORM_COMMON_CLIENT_WRAPPER_INCLUDE_FLUTTER_STANDARD_CODEC_SERIALIZER_H_
#define FLUTTER_SHELL_PLATFORM_COMMON_CLIENT_WRAPPER_INCLUDE_FLUTTER_STANDARD_CODEC_SERIALIZER_H_
 
#include "byte_streams.h"
#include "encodable_value.h"
 
namespace flutter {
 
// Encapsulates the logic for encoding/decoding EncodableValues to/from the
// standard codec binary representation.
//
// This can be subclassed to extend the standard codec with support for new
// types.
class StandardCodecSerializer {
 public:
  virtual ~StandardCodecSerializer();
 
  // Returns the shared serializer instance.
  static const StandardCodecSerializer& GetInstance();
 
  // Prevent copying.
  StandardCodecSerializer(StandardCodecSerializer const&) = delete;
  StandardCodecSerializer& operator=(StandardCodecSerializer const&) = delete;
 
  // Reads and returns the next value from |stream|.
  EncodableValue ReadValue(ByteStreamReader* stream) const;
 
  // Writes the encoding of |value| to |stream|, including the initial type
  // discrimination byte.
  //
  // Can be overridden by a subclass to extend the codec.
  virtual void WriteValue(const EncodableValue& value,
                          ByteStreamWriter* stream) const;
 
 protected:
  // Codecs require long-lived serializers, so clients should always use
  // GetInstance().
  StandardCodecSerializer();
 
  // Reads and returns the next value from |stream|, whose discrimination byte
  // was |type|.
  //
  // The discrimination byte will already have been read from the stream when
  // this is called.
  //
  // Can be overridden by a subclass to extend the codec.
  virtual EncodableValue ReadValueOfType(uint8_t type,
                                         ByteStreamReader* stream) const;
 
  // Reads the variable-length size from the current position in |stream|.
  size_t ReadSize(ByteStreamReader* stream) const;
 
  // Writes the variable-length size encoding to |stream|.
  void WriteSize(size_t size, ByteStreamWriter* stream) const;
 
 private:
  // Reads a fixed-type list whose values are of type T from the current
  // position in |stream|, and returns it as the corresponding EncodableValue.
  // |T| must correspond to one of the supported list value types of
  // EncodableValue.
  template <typename T>
  EncodableValue ReadVector(ByteStreamReader* stream) const;
 
  // Writes |vector| to |stream| as a fixed-type list. |T| must correspond to
  // one of the supported list value types of EncodableValue.
  template <typename T>
  void WriteVector(const std::vector<T> vector, ByteStreamWriter* stream) const;
};
 
}  // namespace flutter
 
#endif  // FLUTTER_SHELL_PLATFORM_COMMON_CLIENT_WRAPPER_INCLUDE_FLUTTER_STANDARD_CODEC_SERIALIZER_H_