lokinet/llarp/util/logging/buffer.hpp

#pragma once

#include <llarp/util/buffer.hpp>
#include <llarp/util/formattable.hpp>

#include <string_view>
#include <type_traits>
#include <cstddef>
#include <iosfwd>

namespace llarp
{
  // Buffer printer lets you print a string as a nicely formatted buffer with a hex breakdown and
  // visual representation of the data for logging purposes.  Wraps the string data with a object
  // that prints the buffer format during output; use as:
  //
  //   fmt::print("{}", buffer_printer(my_buffer));
  //
  // or similarly in a log statement.
  //
  struct buffer_printer
  {
    std::basic_string_view<std::byte> buf;

    // Constructed from any type of string_view<T> for a single-byte T (char, std::byte, uint8_t,
    // etc.)
    template <typename T, typename = std::enable_if_t<sizeof(T) == 1>>
    explicit buffer_printer(std::basic_string_view<T> buf)
        : buf{reinterpret_cast<const std::byte*>(buf.data()), buf.size()}
    {}

    // Constructed from any type of lvalue string<T> for a single-byte T (char, std::byte, uint8_t,
    // etc.)
    template <typename T, typename = std::enable_if_t<sizeof(T) == 1>>
    explicit buffer_printer(const std::basic_string<T>& buf)
        : buffer_printer(std::basic_string_view<T>{buf})
    {}

    // *Not* constructable from a string<T> rvalue (because we only hold a view and do not take
    // ownership).
    template <typename T, typename = std::enable_if_t<sizeof(T) == 1>>
    explicit buffer_printer(std::basic_string<T>&& buf) = delete;

    // Constructable from a (T*, size) argument pair, for byte-sized T's.
    template <typename T, typename = std::enable_if_t<sizeof(T) == 1>>
    explicit buffer_printer(const T* data, size_t size)
        : buffer_printer(std::basic_string_view<T>{data, size})
    {}

    // llarp_buffer_t printer:
    explicit buffer_printer(const llarp_buffer_t& buf)
        : buffer_printer(std::basic_string_view<byte_t>{buf.base, buf.sz})
    {}

    std::string
    ToString() const;
  };

  template <>
  constexpr inline bool IsToStringFormattable<buffer_printer> = true;
}  // namespace llarp