<xstd/misc/format/digest.hpp>

std::formatter<boost::hash2::digest<N>>

template<size_t N>
struct formatter<boost::hash2::digest<N>>;

Formats a Boost.Hash2 digest, such as the result of xxh3_128 or of xstd::digest, as hexadecimal.

Format specification

Specification	Output
empty, or x	two lowercase hexadecimal digits per byte, in byte order
X	two uppercase hexadecimal digits per byte, in byte order

Member functions

• parse:
  • Effects: Accepts an empty specification, x or X.
  • Throws: format_error for any other specification. Built with exceptions off, as under -fno-exceptions, it writes the message to stderr and calls std::abort() instead, as libstdc++'s and libc++'s own formatters do.
• format:
  • Effects: Writes two hexadecimal digits per byte, in byte order, lowercase unless the specification is X.

Example

Adapted from the example of std::formatter on cppreference.com, at revision 177164, by cppreference.com contributors. This example is under CC-BY-SA 3.0 and the GFDL, as cppreference.com's content is; the rest of this page is under the Boost Software License.

#include <xstd/misc/format/digest.hpp> // formatter
#include <boost/hash2/digest.hpp>      // digest
#include <format>                      // format
#include <iostream>                    // cout

auto main() -> int
{
        auto const a = boost::hash2::digest<1>({0xbe});
        auto const b = boost::hash2::digest<4>({0xde, 0xad, 0xbe, 0xef});
        std::cout << std::format("To {0} or not to {0}, that is {1}.\n", a, b);
        std::cout << std::format("To {0:x} or not to {0:x}, that is {1:x}.\n", a, b);
        std::cout << std::format("To {0:X} or not to {0:X}, that is {1:X}.\n", a, b);
}

Output:

To be or not to be, that is deadbeef.
To be or not to be, that is deadbeef.
To BE or not to BE, that is DEADBEEF.

See also

Entity	Relation
digest	the class whose result this formats
std::formatter	the standard's formatter, which this specializes