codecs::codec¶

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

template <typename T,
          typename R1 = /* see below */, typename R2 = /* see below */,
          typename IS1 = /* see below */, typename IS2 = /* see below */>
concept codec =
  requires(IS1 is1, IS2 is2) {
    codecs::codec_traits<typename T::traits, IS1, IS2>;

    { T::template encode<R1>(is1) } -> meta::same_as<R1>;
    { T::template decode<R2>(is2) } -> meta::same_as<R2>;
  };

The codec concept specifies the requirements of input encoding/decoding.

It is mgs’ highest-level component.

Notation¶

is1 - value of type IS1
is2 - value of type IS2
Traits - type of typename T::traits
E - type of typename T::traits::default_encoded_output
D - type of typename T::traits::default_decoded_output

Template arguments¶

Definitions¶

R1	Return type of `encode`, defaults to `typename T::traits::default_encoded_output`.
R2	Return type of `decode`, defaults to `typename T::traits::default_decoded_output`.
IS1	Type passed to `encode`, defaults to codecs::iterator_sentinel_source<meta::iterator_t<D>, meta::sentinel_t<D>>.
IS2	Type passed to `decode`, defaults to codecs::iterator_sentinel_source<meta::iterator_t<E>, meta::sentinel_t<E>>.

Constraints¶

Traits	codecs::codec_traits<IS1, IS2>
IS1	codecs::input_source
IS2	codecs::input_source

Valid expressions¶

Expression	Return type
T::template encode<R1>(is1)	`R1`
T::template decode<R2>(is2)	`R2`

Expression semantics¶

Expression	Semantics
T::template decode<R1>(is1)	Encodes the source’s input into a value of type `R1`
T::template decode<R2>(is2)	Decodes the source’s input into a value of type `R2`

Concept emulation¶

namespace mgs {
namespace codecs {

template <typename T,
          typename R1 = /* ... */, typename R2 = /* ... */,
          typename IS1 = /* ... */, typename IS2 = /* ... */>
struct is_codec { /* ... */ };

template <typename T,
          typename R1 = /* ... */, typename R2 = /* ... */,
          typename IS1 = /* ... */, typename IS2 = /* ... */>
constexpr auto is_codec_v = is_codec<T, R1, R2, IS1, IS2>::value;

template <typename T,
          typename R1 = /* ... */, typename R2 = /* ... */,
          typename IS1 = /* ... */, typename IS2 = /* ... */,
          typename = std::enable_if_t<is_codec_v<T, R1, R2, IS1, IS2>>>
using codec = T;

} // namespace codecs
} // namespace mgs

Example¶

#include <mgs/base64.hpp>
#include <mgs/codecs/concepts/codec.hpp>

using namespace mgs::codecs;

int main() {
  static_assert(is_codec_v<base64>, "");
  static_assert(is_codec_v<base64, std::string, std::vector<unsigned char>>, "");
}

See also¶