sha256.hpp

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#ifndef PLSSVM_DETAIL_SHA256_HPP_
#define PLSSVM_DETAIL_SHA256_HPP_
#pragma once
 
#include <array>        // std::array
#include <cstdint>      // std::uint32_t
#include <string>       // std::string
#include <type_traits>  // std::enable_if_t, std::is_unsigned_v
 
namespace plssvm::detail {
 
class sha256 {
  public:
    [[nodiscard]] std::string operator()(std::string input) const;
 
  private:
    template <typename T, std::enable_if_t<std::is_unsigned_v<T>, bool> = true>
    static void unpack(const T x, unsigned char *str) {
        for (std::size_t i = 0; i < sizeof(T); ++i) {
            str[i] = static_cast<unsigned char>(x >> ((sizeof(T) - i - 1) * 8));
        }
    }
    static void pack32(const unsigned char *str, std::uint32_t &x);
    [[nodiscard]] static std::uint32_t rotr32(std::uint32_t value, unsigned int count);
 
    static constexpr std::uint32_t DIGEST_SIZE = 256 / 8;
    static constexpr std::uint32_t CHUNK_SIZE = 512 / 8;
 
    static constexpr std::array<std::uint32_t, 64> k_{
        // clang-format off
        0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
        0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
        0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
        0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
        0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
        0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
        0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
        0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
        // clang-format on
    };
};
 
}  // namespace plssvm::detail
 
#endif  // PLSSVM_DETAIL_SHA256_HPP_