sha2_512_256.h

/*
 *  Chocobo1/Hash
 *
 *   Copyright 2017-2020 by Mike Tzou (Chocobo1)
 *     https://github.com/Chocobo1/Hash
 *
 *   Licensed under GNU General Public License 3 or later.
 *
 *  @license GPL3 <https://www.gnu.org/licenses/gpl-3.0-standalone.html>
 */

#ifndef CHOCOBO1_SHA2_512_256_H
#define CHOCOBO1_SHA2_512_256_H

#include <array>
#include <cassert>
#include <climits>
#include <cmath>
#include <cstdint>
#include <initializer_list>
#include <string>
#include <type_traits>
#include <vector>

#if (__cplusplus > 201703L)
#include <version>
#endif

#ifndef USE_STD_SPAN_CHOCOBO1_HASH
#if (__cpp_lib_span >= 202002L)
#define USE_STD_SPAN_CHOCOBO1_HASH 1
#else
#define USE_STD_SPAN_CHOCOBO1_HASH 0
#endif
#endif

#if (USE_STD_SPAN_CHOCOBO1_HASH == 1)
#include <span>
#else
#include "gsl/span"
#endif


namespace Chocobo1
{
    // Use these!!
    // SHA2_512_256();
}


namespace Chocobo1
{
// users should ignore things in this namespace

    namespace Hash
    {
#ifndef CONSTEXPR_CPP17_CHOCOBO1_HASH
#if __cplusplus >= 201703L
#define CONSTEXPR_CPP17_CHOCOBO1_HASH constexpr
#else
#define CONSTEXPR_CPP17_CHOCOBO1_HASH
#endif
#endif

#if (USE_STD_SPAN_CHOCOBO1_HASH == 1)
        using IndexType = std::size_t;
#else
        using IndexType = gsl::index;
#endif

#ifndef CHOCOBO1_HASH_BUFFER_IMPL
#define CHOCOBO1_HASH_BUFFER_IMPL
        template <typename T, IndexType N>
        class Buffer
        {
        public:
            using value_type = T;
            using index_type = IndexType;
            using size_type = std::size_t;

            constexpr Buffer() = default;
            constexpr Buffer(const Buffer &) = default;

            constexpr Buffer(const std::initializer_list<T> initList)
            {
#if !defined(NDEBUG)
                // check if out-of-bounds
                static_cast<void>(m_array.at(m_dataEndIdx + initList.size() - 1));
#endif

                for (const auto &i : initList)
                {
                    m_array[m_dataEndIdx] = i;
                    ++m_dataEndIdx;
                }
            }

            template <typename InputIt>
            constexpr Buffer(const InputIt first, const InputIt last)
            {
                for (InputIt iter = first; iter != last; ++iter)
                {
                    this->fill(*iter);
                }
            }

            constexpr T& operator[](const index_type pos)
            {
                return m_array[pos];
            }

            constexpr T operator[](const index_type pos) const
            {
                return m_array[pos];
            }

            constexpr void fill(const T &value, const index_type count = 1)
            {
#if !defined(NDEBUG)
                // check if out-of-bounds
                static_cast<void>(m_array.at(m_dataEndIdx + count - 1));
#endif

                for (index_type i = 0; i < count; ++i)
                {
                    m_array[m_dataEndIdx] = value;
                    ++m_dataEndIdx;
                }
            }

            template <typename InputIt>
            constexpr void push_back(const InputIt first, const InputIt last)
            {
                for (InputIt iter = first; iter != last; ++iter)
                {
                    this->fill(*iter);
                }
            }

            constexpr void clear()
            {
                m_array = {};
                m_dataEndIdx = 0;
            }

            constexpr bool empty() const
            {
                return (m_dataEndIdx == 0);
            }

            constexpr size_type size() const
            {
                return m_dataEndIdx;
            }

            constexpr const T* data() const
            {
                return m_array.data();
            }

        private:
            std::array<T, N> m_array {};
            index_type m_dataEndIdx = 0;
        };
#endif

#ifndef CHOCOBO1_HASH_UINT128_IMPL
#define CHOCOBO1_HASH_UINT128_IMPL
        class Uint128
        {
        public:
            constexpr Uint128()
                    : m_lo(0), m_hi(0)
            {
            }

            constexpr Uint128& operator= (const uint64_t n)
            {
                this->m_lo = n;
                this->m_hi = 0;
                return (*this);
            }

            constexpr Uint128 operator+ (const uint64_t n)
            {
                Uint128 ret = *this;
                ret += n;
                return ret;
            }

            constexpr Uint128& operator* (const unsigned int n)
            {
                // only handle `*8` case
                assert(n == 8);

                const uint8_t msb = static_cast<uint8_t>(m_lo >> 61);
                m_hi = (m_hi << 3) | msb;
                m_lo = m_lo << 3;

                return (*this);
            }

            constexpr Uint128& operator+= (const uint64_t n)
            {
                const uint64_t newLo = (m_lo + n);
                if (newLo < m_lo)
                    ++m_hi;
                m_lo = newLo;

                return (*this);
            }

            constexpr uint64_t low() const
            {
                return m_lo;
            }

            constexpr uint64_t high() const
            {
                return m_hi;
            }

        private:
            uint64_t m_lo;
            uint64_t m_hi;
        };
#endif


        namespace SHA2_512_256_NS
        {
            class SHA2_512_256
            {
                // https://dx.doi.org/10.6028/NIST.FIPS.180-4

            public:
                using Byte = uint8_t;
                using ResultArrayType = std::array<Byte, 32>;

#if (USE_STD_SPAN_CHOCOBO1_HASH == 1)
                template <typename T, std::size_t Extent = std::dynamic_extent>
			using Span = std::span<T, Extent>;
#else
                template <typename T, std::size_t Extent = gsl::dynamic_extent>
                using Span = gsl::span<T, Extent>;
#endif


                constexpr SHA2_512_256();

                constexpr void reset();
                CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_512_256& finalize();  // after this, only `toArray()`, `toString()`, `toVector()`, `reset()` are available

                std::string toString() const;
                std::vector<Byte> toVector() const;
                CONSTEXPR_CPP17_CHOCOBO1_HASH ResultArrayType toArray() const;

                CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_512_256& addData(const Span<const Byte> inData);
                CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_512_256& addData(const void *ptr, const std::size_t length);
                template <std::size_t N>
                CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_512_256& addData(const Byte (&array)[N]);
                template <typename T, std::size_t N>
                SHA2_512_256& addData(const T (&array)[N]);
                template <typename T>
                SHA2_512_256& addData(const Span<T> inSpan);

            private:
                CONSTEXPR_CPP17_CHOCOBO1_HASH void addDataImpl(const Span<const Byte> data);

                static constexpr int BLOCK_SIZE = 128;

                Buffer<Byte, (BLOCK_SIZE * 2)> m_buffer;  // x2 for paddings
                Uint128 m_sizeCounter;

                uint64_t m_h[8] = {};

                static constexpr uint64_t kTable[80] =
                        {
                                0x428a2f98d728ae22, 0x7137449123ef65cd, 0xb5c0fbcfec4d3b2f, 0xe9b5dba58189dbbc,
                                0x3956c25bf348b538, 0x59f111f1b605d019, 0x923f82a4af194f9b, 0xab1c5ed5da6d8118,
                                0xd807aa98a3030242, 0x12835b0145706fbe, 0x243185be4ee4b28c, 0x550c7dc3d5ffb4e2,
                                0x72be5d74f27b896f, 0x80deb1fe3b1696b1, 0x9bdc06a725c71235, 0xc19bf174cf692694,
                                0xe49b69c19ef14ad2, 0xefbe4786384f25e3, 0x0fc19dc68b8cd5b5, 0x240ca1cc77ac9c65,
                                0x2de92c6f592b0275, 0x4a7484aa6ea6e483, 0x5cb0a9dcbd41fbd4, 0x76f988da831153b5,
                                0x983e5152ee66dfab, 0xa831c66d2db43210, 0xb00327c898fb213f, 0xbf597fc7beef0ee4,
                                0xc6e00bf33da88fc2, 0xd5a79147930aa725, 0x06ca6351e003826f, 0x142929670a0e6e70,
                                0x27b70a8546d22ffc, 0x2e1b21385c26c926, 0x4d2c6dfc5ac42aed, 0x53380d139d95b3df,
                                0x650a73548baf63de, 0x766a0abb3c77b2a8, 0x81c2c92e47edaee6, 0x92722c851482353b,
                                0xa2bfe8a14cf10364, 0xa81a664bbc423001, 0xc24b8b70d0f89791, 0xc76c51a30654be30,
                                0xd192e819d6ef5218, 0xd69906245565a910, 0xf40e35855771202a, 0x106aa07032bbd1b8,
                                0x19a4c116b8d2d0c8, 0x1e376c085141ab53, 0x2748774cdf8eeb99, 0x34b0bcb5e19b48a8,
                                0x391c0cb3c5c95a63, 0x4ed8aa4ae3418acb, 0x5b9cca4f7763e373, 0x682e6ff3d6b2b8a3,
                                0x748f82ee5defb2fc, 0x78a5636f43172f60, 0x84c87814a1f0ab72, 0x8cc702081a6439ec,
                                0x90befffa23631e28, 0xa4506cebde82bde9, 0xbef9a3f7b2c67915, 0xc67178f2e372532b,
                                0xca273eceea26619c, 0xd186b8c721c0c207, 0xeada7dd6cde0eb1e, 0xf57d4f7fee6ed178,
                                0x06f067aa72176fba, 0x0a637dc5a2c898a6, 0x113f9804bef90dae, 0x1b710b35131c471b,
                                0x28db77f523047d84, 0x32caab7b40c72493, 0x3c9ebe0a15c9bebc, 0x431d67c49c100d4c,
                                0x4cc5d4becb3e42b6, 0x597f299cfc657e2a, 0x5fcb6fab3ad6faec, 0x6c44198c4a475817
                        };
            };

            constexpr uint64_t SHA2_512_256::kTable[80];


            // helpers
            template <typename T>
            class Loader
            {
                // this class workaround loading data from unaligned memory boundaries
                // also eliminate endianness issues
            public:
                explicit constexpr Loader(const void *ptr)
                        : m_ptr(static_cast<const uint8_t *>(ptr))
                {
                }

                constexpr T operator[](const IndexType idx) const
                {
                    static_assert(std::is_same<T, uint64_t>::value, "");
                    // handle specific endianness here
                    const uint8_t *ptr = m_ptr + (sizeof(T) * idx);
                    return  ( (static_cast<T>(*(ptr + 0)) << 56)
                              | (static_cast<T>(*(ptr + 1)) << 48)
                              | (static_cast<T>(*(ptr + 2)) << 40)
                              | (static_cast<T>(*(ptr + 3)) << 32)
                              | (static_cast<T>(*(ptr + 4)) << 24)
                              | (static_cast<T>(*(ptr + 5)) << 16)
                              | (static_cast<T>(*(ptr + 6)) <<  8)
                              | (static_cast<T>(*(ptr + 7)) <<  0));
                }

            private:
                const uint8_t *m_ptr;
            };

            template <typename R, typename T>
            constexpr R ror(const T x, const unsigned int s)
            {
                static_assert(std::is_unsigned<R>::value, "");
                static_assert(std::is_unsigned<T>::value, "");
                return static_cast<R>(x >> s);
            }

            template <typename T>
            constexpr T rotr(const T x, const unsigned int s)
            {
                static_assert(std::is_unsigned<T>::value, "");
                if (s == 0)
                    return x;
                return ((x >> s) | (x << ((sizeof(T) * 8) - s)));
            }


            constexpr SHA2_512_256::SHA2_512_256()
            {
                static_assert((CHAR_BIT == 8), "Sorry, we don't support exotic CPUs");
                reset();
            }

            constexpr void SHA2_512_256::reset()
            {
                m_buffer.clear();
                m_sizeCounter = 0;

                m_h[0] = 0x22312194FC2BF72C;
                m_h[1] = 0x9F555FA3C84C64C2;
                m_h[2] = 0x2393B86B6F53B151;
                m_h[3] = 0x963877195940EABD;
                m_h[4] = 0x96283EE2A88EFFE3;
                m_h[5] = 0xBE5E1E2553863992;
                m_h[6] = 0x2B0199FC2C85B8AA;
                m_h[7] = 0x0EB72DDC81C52CA2;
            }

            CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_512_256& SHA2_512_256::finalize()
            {
                m_sizeCounter += m_buffer.size();

                // append 1 bit
                m_buffer.fill(1 << 7);

                // append paddings
                const size_t len = BLOCK_SIZE - ((m_buffer.size() + 16) % BLOCK_SIZE);
                m_buffer.fill(0, (len + 16));

                // append size in bits
                const Uint128 sizeCounterBits = m_sizeCounter * 8;
                const uint64_t sizeCounterBitsL = sizeCounterBits.low();
                const uint64_t sizeCounterBitsH = sizeCounterBits.high();
                for (int i = 0; i < 8; ++i)
                {
                    m_buffer[m_buffer.size() - 16 + i] = ror<Byte>(sizeCounterBitsH, (8 * (7 - i)));
                    m_buffer[m_buffer.size() - 8 + i] = ror<Byte>(sizeCounterBitsL, (8 * (7 - i)));
                }

                addDataImpl({m_buffer.data(), m_buffer.size()});
                m_buffer.clear();

                return (*this);
            }

            std::string SHA2_512_256::toString() const
            {
                const auto a = toArray();
                std::string ret;
                ret.resize(2 * a.size());

                auto retPtr = &ret.front();
                for (const auto c : a)
                {
                    const Byte upper = ror<Byte>(c, 4);
                    *(retPtr++) = static_cast<char>((upper < 10) ? (upper + '0') : (upper - 10 + 'a'));

                    const Byte lower = c & 0xf;
                    *(retPtr++) = static_cast<char>((lower < 10) ? (lower + '0') : (lower - 10 + 'a'));
                }

                return ret;
            }

            std::vector<SHA2_512_256::Byte> SHA2_512_256::toVector() const
            {
                const auto a = toArray();
                return {a.begin(), a.end()};
            }

            CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_512_256::ResultArrayType SHA2_512_256::toArray() const
            {
                const Span<const uint64_t> state(m_h, 4);
                const int dataSize = sizeof(decltype(state)::value_type);

                ResultArrayType ret {};
                auto retPtr = ret.data();
                for (const auto i : state)
                {
                    for (int j = (dataSize - 1); j >= 0; --j)
                        *(retPtr++) = ror<Byte>(i, (j * 8));
                }

                return ret;
            }

            CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_512_256& SHA2_512_256::addData(const Span<const Byte> inData)
            {
                Span<const Byte> data = inData;

                if (!m_buffer.empty())
                {
                    const size_t len = std::min<size_t>((BLOCK_SIZE - m_buffer.size()), data.size());  // try fill to BLOCK_SIZE bytes
                    m_buffer.push_back(data.begin(), (data.begin() + len));

                    if (m_buffer.size() < BLOCK_SIZE)  // still doesn't fill the buffer
                        return (*this);

                    addDataImpl({m_buffer.data(), m_buffer.size()});
                    m_buffer.clear();

                    data = data.subspan(len);
                }

                const size_t dataSize = data.size();
                if (dataSize < BLOCK_SIZE)
                {
                    m_buffer = {data.begin(), data.end()};
                    return (*this);
                }

                const size_t len = dataSize - (dataSize % BLOCK_SIZE);  // align on BLOCK_SIZE bytes
                addDataImpl(data.first(len));

                if (len < dataSize)  // didn't consume all data
                    m_buffer = {(data.begin() + len), data.end()};

                return (*this);
            }

            CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_512_256& SHA2_512_256::addData(const void *ptr, const std::size_t length)
            {
                // Span::size_type = std::size_t
                return addData({static_cast<const Byte*>(ptr), length});
            }

            template <std::size_t N>
            CONSTEXPR_CPP17_CHOCOBO1_HASH SHA2_512_256& SHA2_512_256::addData(const Byte (&array)[N])
            {
                return addData({array, N});
            }

            template <typename T, std::size_t N>
            SHA2_512_256& SHA2_512_256::addData(const T (&array)[N])
            {
                return addData({reinterpret_cast<const Byte*>(array), (sizeof(T) * N)});
            }

            template <typename T>
            SHA2_512_256& SHA2_512_256::addData(const Span<T> inSpan)
            {
                return addData({reinterpret_cast<const Byte*>(inSpan.data()), inSpan.size_bytes()});
            }

            CONSTEXPR_CPP17_CHOCOBO1_HASH void SHA2_512_256::addDataImpl(const Span<const Byte> data)
            {
                assert((data.size() % BLOCK_SIZE) == 0);

                m_sizeCounter += data.size();

                for (size_t iter = 0, iend = static_cast<size_t>(data.size() / BLOCK_SIZE); iter < iend; ++iter)
                {
                    const Loader<uint64_t> m(static_cast<const Byte *>(data.data() + (iter * BLOCK_SIZE)));

                    // TODO: kTable was here, move it back when static variable in constexpr function is allowed

                    const auto ssig0 = [](const uint64_t x) -> uint64_t
                    {
                        return (rotr(x, 1) ^ rotr(x, 8) ^ ror<uint64_t>(x, 7));
                    };
                    const auto ssig1 = [](const uint64_t x) -> uint64_t
                    {
                        return (rotr(x, 19) ^ rotr(x, 61) ^ ror<uint64_t>(x, 6));
                    };
                    uint64_t wTable[80] {};
                    for (int t = 0; t < 16; ++t)
                        wTable[t] = m[t];
                    for (int t = 16; t < 80; ++t)
                        wTable[t] = ssig1(wTable[t - 2]) + wTable[t - 7] + ssig0(wTable[t - 15]) + wTable[t - 16];

                    uint64_t a = m_h[0];
                    uint64_t b = m_h[1];
                    uint64_t c = m_h[2];
                    uint64_t d = m_h[3];
                    uint64_t e = m_h[4];
                    uint64_t f = m_h[5];
                    uint64_t g = m_h[6];
                    uint64_t h = m_h[7];

                    const auto round = [&wTable](uint64_t &a, uint64_t &b, uint64_t &c, uint64_t &d, uint64_t &e, uint64_t &f, uint64_t &g, uint64_t &h, const unsigned int t) -> void
                    {
                        const auto ch = [](const uint64_t x, const uint64_t y, const uint64_t z) -> uint64_t
                        {
                            return ((x & (y ^ z)) ^ z);  // alternative
                        };
                        const auto maj = [](const uint64_t x, const uint64_t y, const uint64_t z) -> uint64_t
                        {
                            return ((x & (y | z)) | (y & z));  // alternative
                        };
                        const auto bsig0 = [](const uint64_t x) -> uint64_t
                        {
                            return (rotr(x, 28) ^ rotr(x, 34) ^ rotr(x, 39));
                        };
                        const auto bsig1 = [](const uint64_t x) -> uint64_t
                        {
                            return (rotr(x, 14) ^ rotr(x, 18) ^ rotr(x, 41));
                        };

                        const uint64_t t1 = h + bsig1(e) + ch(e, f, g) + kTable[t] + wTable[t];
                        const uint64_t t2 = bsig0(a) + maj(a, b, c);

                        h = t1;
                        d += h;
                        h += t2;
                    };
                    for (int t = 0; t < 10; ++t)
                    {
                        round(a, b, c, d, e, f, g, h, (8 * t) + 0);
                        round(h, a, b, c, d, e, f, g, (8 * t) + 1);
                        round(g, h, a, b, c, d, e, f, (8 * t) + 2);
                        round(f, g, h, a, b, c, d, e, (8 * t) + 3);
                        round(e, f, g, h, a, b, c, d, (8 * t) + 4);
                        round(d, e, f, g, h, a, b, c, (8 * t) + 5);
                        round(c, d, e, f, g, h, a, b, (8 * t) + 6);
                        round(b, c, d, e, f, g, h, a, (8 * t) + 7);
                    }

                    m_h[0] += a;
                    m_h[1] += b;
                    m_h[2] += c;
                    m_h[3] += d;
                    m_h[4] += e;
                    m_h[5] += f;
                    m_h[6] += g;
                    m_h[7] += h;
                }
            }
        }
    }
    using SHA2_512_256 = Hash::SHA2_512_256_NS::SHA2_512_256;
}

#endif  // CHOCOBO1_SHA2_512_256_H