codecs::codec_output

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

#include <mgs/codecs/output_traits_fwd.hpp>

template <typename T, typename R>
concept codec_output =
  meta::input_range<R> &&
  requires (R& range) {
    { codecs::output_traits<T>::create(range) } -> meta::same_as<T>;
  };

The codec_output concept specifies the requirements that a type must fulfill in order to be returned by a codecs::codec.

It relies on the customization point codecs::output_traits.

---

Notation

• r - a value of type R&

Template arguments

Definitions

R	Input range from which T must be created.

Constraints

R	meta::input_range

Valid expressions

Expressions	Return type
output_traits<T>::create(r)	T

Expression semantics

Expressions	Semantics
output_traits<T>::create(r)	Creates and returns a T from r ‘s input.

Concept emulation

namespace mgs {
namespace codecs {

template <typename T, typename R>
struct is_codec_output { /* ... */ };

template <typename T, typename R>
constexpr auto is_codec_output_v = is_codec_output<T, R>::value;

template <typename T, typename R,
          typename = std::enable_if_t<is_codec_output_v<T, R>>>
using codec_output = T;

} // namespace codecs
} // namespace mgs

Example

#include <algorithm>

#include <mgs/codecs/output_traits_fwd.hpp>
#include <mgs/codecs/concepts/codec_output.hpp>
#include <mgs/codecs/iterator_sentinel_source.hpp>

#include <mgs/base64.hpp>

#include <QLinkedList>
#include <QList>

// add support for QLinkedList
namespace mgs {
namespace codecs {

template <typename CharT>
struct output_traits<QLinkedList<CharT>> {

  template <typename R>
  static QLinkedList<CharT> create(R& range) {
    QLinkedList<CharT> list;
    std::copy(range.begin(), range.end(), std::back_inserter(list));
    return list;
  }
};

} // namespace codecs
} // namespace mgs

using namespace mgs;
using namespace mgs::codecs;

int main() {
  using encoder = base64::encoder<codecs::iterator_sentinel_source<char const*>>;

  static_assert(is_codec_output_v<std::string, encoder>, "");
  static_assert(is_codec_output_v<QLinkedList<char>, encoder>, "");

  static_assert(!is_codec_output_v<QList<char>, encoder>, "");
}