base64

A simple, header-only C++17 library for Base64 encoding and decoding. Uses modern C++ features when available (e.g., std::bit_cast in C++20) while remaining portable and efficient.

Features

• Header-only, single-file library
• Fast encoding/decoding using lookup tables
• Safe type punning using std::bit_cast (avoids undefined behavior with unions)
• Throws std::runtime_error for invalid Base64 input (size, padding, or characters)

Platform Support

• Compilers: GCC, Clang, MSVC
• Architectures: x86, x64, ARM, AArch64 (little-endian)
• Requires C++17 (C++20 features optional)

Usage

#include <iostream>  
#include "base64.hpp"  

int main() {  
    auto encoded = base64::to_base64("Hello, World!");  
    std::cout << encoded << std::endl; // SGVsbG8sIFdvcmxkIQ==  

    auto decoded = base64::from_base64("SGVsbG8sIFdvcmxkIQ==");  
    std::cout << decoded << std::endl; // Hello, World!  
}

Notes

• Inspired by Nick Galbreath's modp_b64 (used by Chromium) for high performance
• Compatible with C++17; optionally uses C++20 features
• Avoids union-based type punning for safety
• Faster implementations exist using SIMD or multithreading but are not header-only

References

• Benchmark of C/C++ Base64 libraries: https://github.com/gaspardpetit/base64/
• Chromium modp_b64: https://github.com/chromium/chromium/tree/main/third_party/modp_b64
• SIMD/optimized alternatives:
  • https://github.com/aklomp/base64
  • https://github.com/simdutf/simdutf
  • https://github.com/powturbo/Turbo-Base64