codecs::sized_input_source

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

template <typename T>
concept sized_input_source =
  codecs::input_source<T> &&
  requires(T const& cs) {
    { cv.max_remaining_size() } -> meta::convertible_to<mgs::ssize_t>;
  };

The sized_input_source concept is a refinement of codecs::input_source which can compute the maximum number of remaining bytes.

---

Notation

• cs - value of type T const&

Refinements

• codecs::input_source

Valid expressions

Expression	Return type
cs.max_remaining_size()	meta::convertible_to<mgs::ssize_t>

Expression semantics

Expression	Semantics
cs.max_remaining_size()	Returns the maximum number of remaining bytes

Concept emulation

namespace mgs {
namespace codecs {

template <typename T>
struct is_sized_input_source { /* ... */ };

template <typename T>
constexpr auto is_sized_input_source_v = is_sized_input_source<T>::value;

template <typename T,
          typename = std::enable_if_t<is_sized_input_source_v<T>>>
using sized_input_source = T;

} // namespace codecs
} // namespace mgs

Example

#include <mgs/codecs/concepts/sized_input_source.hpp>

using namespace mgs::codecs;

struct vector_input_source {
  using element_type = unsigned char;

  std::vector<unsigned char> buffer;
  int pos = 0;

  vector_input_source() : buffer(4096) {}

  int read(unsigned char* dst, int n) {
    auto const to_read = std::min<int>(n, buffer.size() - pos);
    std::copy_n(buffer.begin() + pos, to_read, dst);
    pos += to_read;
    return to_read;
  }

  mgs::ssize_t max_remaining_size() const {
    return buffer.size() - pos;
  }
};

static_assert(is_sized_input_source_v<vector_input_source>, "");