base64.h File Reference

Compile-time Base64 and Base64URL codec for the jh::meta subsystem. More...

#include <cstdint>
#include "jh/pods/array.h"
#include "jh/metax/t_str.h"
#include "jh/detail/base64_common.h"

Go to the source code of this file.

Namespaces
namespace	jh::meta
	Aggregated entry point for compile-time metaprogramming utilities.

Functions
template<TStr S>
constexpr auto	jh::meta::decode_base64 ()
	Decode a Base64-encoded TStr literal at compile time.
template<TStr S>
constexpr auto	jh::meta::decode_base64url ()
	Decode a Base64URL-encoded TStr literal at compile time.
template<std::uint16_t N>
constexpr auto	jh::meta::encode_base64 (const jh::pod::array< std::uint8_t, N > &raw)
	Encode a byte buffer into a Base64 literal at compile time.
template<std::uint16_t N, class PadT = std::false_type>
constexpr auto	jh::meta::encode_base64url (const jh::pod::array< std::uint8_t, N > &raw, PadT={})
	Encode a byte buffer into a Base64URL literal at compile time.

Detailed Description

Compile-time Base64 and Base64URL codec for the jh::meta subsystem.

Copyright

Copyright 2025 JeongHan-Bae <mastropseudo@gmail.com>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Full license: GitHub

Author

JeongHan-Bae <mastropseudo@gmail.com>

This header provides a fully constexpr-capable Base64 and Base64URL codec that operates entirely at compile time. Encoded text is supplied as a non-type template parameter (NTTP) through the TStr compile-time string type.
The jh::meta subsystem focuses on compile-time reflection, static string manipulation, and deterministic constexpr evaluation. Its Base64 facilities allow encoded data to be decoded or generated during compilation, enabling static asset embedding, protocol constant generation, and zero-runtime preprocessing.

Design overview

• Implements Base64 (RFC 4648 §4) with padding.
• Implements Base64URL (RFC 4648 §5) with optional padding.
• All constraints (is_base64, is_base64url) are validated at compile time.
• Decode functions return jh::pod::array<std::uint8_t, N>.
• Encode functions return t_str<M> with a built-in null terminator.
• Supports round-trip transformations between t_str and byte buffers.

Usage

Compile-time decoding using a literal NTTP:

constexpr auto decoded = jh::meta::decode_base64<"Qm9i">();   // "Bob"

Compile-time decoding using a macro-defined literal:

#ifndef BASE64_STR_DEMO
#define BASE64_STR_DEMO "SGkh"
#endif
constexpr auto decoded = jh::meta::decode_base64<BASE64_STR_DEMO>();
// "Hi!"

Full round-trip example using t_str and byte buffers:

// original "Hello"
constexpr jh::meta::t_str str{"Hello"};
 
// string → bytes
constexpr auto bytes = str.to_bytes();
 
// bytes → base64 literal
constexpr auto encoded = jh::meta::encode_base64(bytes);
 
// base64 → bytes
constexpr auto decoded = jh::meta::decode_base64<encoded>();
 
// bytes → t_str
constexpr auto restored =
    jh::meta::t_str<decoded.size() + 1>::from_bytes(decoded);

Subsystem role

Within the jh::meta subsystem, this file provides the compile-time counterpart to the runtime Base64 codec used in the serialization module. While the runtime interface focuses on interoperability and safety, the compile-time interface focuses on deterministic evaluation, static transformation of encoded resources, and NTTP-based metaprogramming.

Version

1.4.x

Date

2025