codecs::codec_traits¶

Defined in header <mgs/codecs/concepts/codec_traits.hpp>

// exposition only
template <typename T, typename IS>
using encoder = decltype(T::make_encoder(std::declval<IS>());

// exposition only
template <typename T, typename IS>
using decoder = decltype(T::make_decoder(std::declval<IS>());

template <typename T,
          typename IS1 = /* see below */, typename IS2 = /* see below */>
concept codec_traits =
  codecs::input_source<IS1> &&
  codecs::input_source<IS2> &&
  requires(IS1 is1, IS2 is2) {
    { T::make_encoder(is1) } -> meta::input_range;
    { T::make_decoder(is2) } -> meta::input_range;
    codecs::codec_output<typename T::default_encoded_output, encoder<T, IS1>>;
    codecs::codec_output<typename T::default_decoded_output, decoder<T, IS2>>;
  };

The codec_traits concept specifies that a type can create encoders and decoders for a specific codec, and defines default encoded and decoded types.

Notation¶

is1 - value of type IS1
is2 - value of type IS2
Encoder - type returned by T::make_encoder(is1)
Decoder - type returned by T::make_decoder(is2)
E - type alias of typename T::traits::default_encoded_output
D - type alias of typename T::traits::default_decoded_output

Member types¶

Definitions¶

default_encoded_output	Type to be used by default by a codecs::codec when encoding
default_decoded_output	Type to be used by default by a codecs::codec when decoding

Constraints¶

default_encoded_output	codecs::codec_output<Encoder>
default_decoded_output	codecs::codec_output<Decoder>

Template arguments¶

Definitions¶

IS1	Type passed to `make_encoder`, defaults to codecs::iterator_sentinel_source<meta::iterator_t<D>, meta::sentinel_t<D>>.
IS2	Type passed to `make_decoder`, defaults to codecs::iterator_sentinel_source<meta::iterator_t<E>, meta::sentinel_t<E>>.

Constraints¶

IS1	codecs::input_source
IS2	codecs::input_source

Valid expressions¶

Expression	Return type
T::make_encoder(is1)	meta::input_range
T::make_decoder(is2)	meta::input_range

Expression semantics¶

Expression	Semantics
T::make_encoder(is1)	Creates an encoder from the input source
T::make_decoder(is2)	Creates a decoder from the input source

Concept emulation¶

namespace mgs {
namespace codecs {

template <typename T,
          typename IS1 = /* ... */, typename IS2 = /* ... */>
struct is_codec_traits { /* ... */ };

template <typename T,
          typename IS1 = /* ... */, typename IS2 = /* ... */>
constexpr auto is_codec_traits_v = is_codec_traits<T, IS1, IS2>::value;

template <typename T,
          typename IS1 = /* ... */, typename IS2 = /* ... */,
          typename = std::enable_if_t<is_codec_traits_v<T, IS1, IS2>>>
using codec_traits = T;

} // namespace codecs
} // namespace mgs

Example¶

#include <string>
#include <vector>

#include <mgs/codecs/concepts/codec_traits.hpp>
#include <mgs/codecs/basic_input_range.hpp>

using namespace mgs;
using namespace mgs::codecs;

class noop_traits {
private:
  using input_source = iterator_sentinel_source<char const*>;
  using noop_encoder = basic_input_range<input_source>;
  using noop_decoder = noop_encoder

public:
  using default_encoded_output = std::string;
  using default_decoded_output = default_encoded_output;


  static noop_encoder make_encoder(input_source is) {
     return noop_encoder(is);
  }

  static noop_decoder make_decoder(input_source is) {
     return noop_decoder(is);
  }
};

int main() {
  static_assert(is_codec_traits_v<noop_traits>::value, "");
}

See also¶