text: // Copyright (c) 2014 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "crypto/sha256.h"
  
  #include "crypto/common.h"
  
  #include <cstring>
  
  // Internal implementation code.
  namespace {
  /// Internal SHA-256 implementation.
  namespace sha256 {
      inline uint32_t Ch(uint32_t x, uint32_t y, uint32_t z) {
          return z ^ (x & (y ^ z));
      }
      inline uint32_t Maj(uint32_t x, uint32_t y, uint32_t z) {
          return (x & y) | (z & (x | y));
      }
      inline uint32_t Sigma0(uint32_t x) {
          return (x >> 2 | x << 30) ^ (x >> 13 | x << 19) ^ (x >> 22 | x << 10);
      }
      inline uint32_t Sigma1(uint32_t x) {
          return (x >> 6 | x << 26) ^ (x >> 11 | x << 21) ^ (x >> 25 | x << 7);
      }
      inline uint32_t sigma0(uint32_t x) {
          return (x >> 7 | x << 25) ^ (x >> 18 | x << 14) ^ (x >> 3);
      }
      inline uint32_t sigma1(uint32_t x) {
          return (x >> 17 | x << 15) ^ (x >> 19 | x << 13) ^ (x >> 10);
      }
  
      /** One round of SHA-256. */
      inline void Round(uint32_t a, uint32_t b, uint32_t c, uint32_t &d,
                        uint32_t e, uint32_t f, uint32_t g, uint32_t &h,
                        uint32_t k, uint32_t w) {
          uint32_t t1 = h + Sigma1(e) + Ch(e, f, g) + k + w;
          uint32_t t2 = Sigma0(a) + Maj(a, b, c);
          d += t1;
          h = t1 + t2;
      }
  
      /** Initialize SHA-256 state. */
      inline void Initialize(uint32_t *s) {
          s[0] = 0x6a09e667ul;
          s[1] = 0xbb67ae85ul;
          s[2] = 0x3c6ef372ul;
          s[3] = 0xa54ff53aul;
          s[4] = 0x510e527ful;
          s[5] = 0x9b05688cul;
          s[6] = 0x1f83d9abul;
          s[7] = 0x5be0cd19ul;
      }
  
      /** Perform one SHA-256 transformation, processing a 64-byte chunk. */
      void Transform(uint32_t *s, const uint8_t *chunk) {
          uint32_t a = s[0], b = s[1], c = s[2], d = s[3], e = s[4], f = s[5],
                   g = s[6], h = s[7];
          uint32_t w0, w1, w2, w3, w4, w5, w6, w7, w8, w9, w10, w11, w12, w13,
              w14, w15;
  
          Round(a, b, c, d, e, f, g, h, 0x428a2f98, w0 = ReadBE32(chunk + 0));
          Round(h, a, b, c, d, e, f, g, 0x71374491, w1 = ReadBE32(chunk + 4));
          Round(g, h, a, b, c, d, e, f, 0xb5c0fbcf, w2 = ReadBE32(chunk + 8));
          Round(f, g, h, a, b, c, d, e, 0xe9b5dba5, w3 = ReadBE32(chunk + 12));
          Round(e, f, g, h, a, b, c, d, 0x3956c25b, w4 = ReadBE32(chunk + 16));
          Round(d, e, f, g, h, a, b, c, 0x59f111f1, w5 = ReadBE32(chunk + 20));
          Round(c, d, e, f, g, h, a, b, 0x923f82a4, w6 = ReadBE32(chunk + 24));
          Round(b, c, d, e, f, g, h, a, 0xab1c5ed5, w7 = ReadBE32(chunk + 28));
          Round(a, b, c, d, e, f, g, h, 0xd807aa98, w8 = ReadBE32(chunk + 32));
          Round(h, a, b, c, d, e, f, g, 0x12835b01, w9 = ReadBE32(chunk + 36));
          Round(g, h, a, b, c, d, e, f, 0x243185be, w10 = ReadBE32(chunk + 40));
          Round(f, g, h, a, b, c, d, e, 0x550c7dc3, w11 = ReadBE32(chunk + 44));
          Round(e, f, g, h, a, b, c, d, 0x72be5d74, w12 = ReadBE32(chunk + 48));
          Round(d, e, f, g, h, a, b, c, 0x80deb1fe, w13 = ReadBE32(chunk + 52));
          Round(c, d, e, f, g, h, a, b, 0x9bdc06a7, w14 = ReadBE32(chunk + 56));
          Round(b, c, d, e, f, g, h, a, 0xc19bf174, w15 = ReadBE32(chunk + 60));
  
          Round(a, b, c, d, e, f, g, h, 0xe49b69c1,
                w0 += sigma1(w14) + w9 + sigma0(w1));
          Round(h, a, b, c, d, e, f, g, 0xefbe4786,
                w1 += sigma1(w15) + w10 + sigma0(w2));
          Round(g, h, a, b, c, d, e, f, 0x0fc19dc6,
                w2 += sigma1(w0) + w11 + sigma0(w3));
          Round(f, g, h, a, b, c, d, e, 0x240ca1cc,
                w3 += sigma1(w1) + w12 + sigma0(w4));
          Round(e, f, g, h, a, b, c, d, 0x2de92c6f,
                w4 += sigma1(w2) + w13 + sigma0(w5));
          Round(d, e, f, g, h, a, b, c, 0x4a7484aa,
                w5 += sigma1(w3) + w14 + sigma0(w6));
          Round(c, d, e, f, g, h, a, b, 0x5cb0a9dc,
                w6 += sigma1(w4) + w15 + sigma0(w7));
          Round(b, c, d, e, f, g, h, a, 0x76f988da,
                w7 += sigma1(w5) + w0 + sigma0(w8));
          Round(a, b, c, d, e, f, g, h, 0x983e5152,
                w8 += sigma1(w6) + w1 + sigma0(w9));
          Round(h, a, b, c, d, e, f, g, 0xa831c66d,
                w9 += sigma1(w7) + w2 + sigma0(w10));
          Round(g, h, a, b, c, d, e, f, 0xb00327c8,
                w10 += sigma1(w8) + w3 + sigma0(w11));
          Round(f, g, h, a, b, c, d, e, 0xbf597fc7,
                w11 += sigma1(w9) + w4 + sigma0(w12));
          Round(e, f, g, h, a, b, c, d, 0xc6e00bf3,
                w12 += sigma1(w10) + w5 + sigma0(w13));
          Round(d, e, f, g, h, a, b, c, 0xd5a79147,
                w13 += sigma1(w11) + w6 + sigma0(w14));
          Round(c, d, e, f, g, h, a, b, 0x06ca6351,
                w14 += sigma1(w12) + w7 + sigma0(w15));
          Round(b, c, d, e, f, g, h, a, 0x14292967,
                w15 += sigma1(w13) + w8 + sigma0(w0));
  
          Round(a, b, c, d, e, f, g, h, 0x27b70a85,
                w0 += sigma1(w14) + w9 + sigma0(w1));
          Round(h, a, b, c, d, e, f, g, 0x2e1b2138,
                w1 += sigma1(w15) + w10 + sigma0(w2));
          Round(g, h, a, b, c, d, e, f, 0x4d2c6dfc,
                w2 += sigma1(w0) + w11 + sigma0(w3));
          Round(f, g, h, a, b, c, d, e, 0x53380d13,
                w3 += sigma1(w1) + w12 + sigma0(w4));
          Round(e, f, g, h, a, b, c, d, 0x650a7354,
                w4 += sigma1(w2) + w13 + sigma0(w5));
          Round(d, e, f, g, h, a, b, c, 0x766a0abb,
                w5 += sigma1(w3) + w14 + sigma0(w6));
          Round(c, d, e, f, g, h, a, b, 0x81c2c92e,
                w6 += sigma1(w4) + w15 + sigma0(w7));
          Round(b, c, d, e, f, g, h, a, 0x92722c85,
                w7 += sigma1(w5) + w0 + sigma0(w8));
          Round(a, b, c, d, e, f, g, h, 0xa2bfe8a1,
                w8 += sigma1(w6) + w1 + sigma0(w9));
          Round(h, a, b, c, d, e, f, g, 0xa81a664b,
                w9 += sigma1(w7) + w2 + sigma0(w10));
          Round(g, h, a, b, c, d, e, f, 0xc24b8b70,
                w10 += sigma1(w8) + w3 + sigma0(w11));
          Round(f, g, h, a, b, c, d, e, 0xc76c51a3,
                w11 += sigma1(w9) + w4 + sigma0(w12));
          Round(e, f, g, h, a, b, c, d, 0xd192e819,
                w12 += sigma1(w10) + w5 + sigma0(w13));
          Round(d, e, f, g, h, a, b, c, 0xd6990624,
                w13 += sigma1(w11) + w6 + sigma0(w14));
          Round(c, d, e, f, g, h, a, b, 0xf40e3585,
                w14 += sigma1(w12) + w7 + sigma0(w15));
          Round(b, c, d, e, f, g, h, a, 0x106aa070,
                w15 += sigma1(w13) + w8 + sigma0(w0));
  
          Round(a, b, c, d, e, f, g, h, 0x19a4c116,
                w0 += sigma1(w14) + w9 + sigma0(w1));
          Round(h, a, b, c, d, e, f, g, 0x1e376c08,
                w1 += sigma1(w15) + w10 + sigma0(w2));
          Round(g, h, a, b, c, d, e, f, 0x2748774c,
                w2 += sigma1(w0) + w11 + sigma0(w3));
          Round(f, g, h, a, b, c, d, e, 0x34b0bcb5,
                w3 += sigma1(w1) + w12 + sigma0(w4));
          Round(e, f, g, h, a, b, c, d, 0x391c0cb3,
                w4 += sigma1(w2) + w13 + sigma0(w5));
          Round(d, e, f, g, h, a, b, c, 0x4ed8aa4a,
                w5 += sigma1(w3) + w14 + sigma0(w6));
          Round(c, d, e, f, g, h, a, b, 0x5b9cca4f,
                w6 += sigma1(w4) + w15 + sigma0(w7));
          Round(b, c, d, e, f, g, h, a, 0x682e6ff3,
                w7 += sigma1(w5) + w0 + sigma0(w8));
          Round(a, b, c, d, e, f, g, h, 0x748f82ee,
                w8 += sigma1(w6) + w1 + sigma0(w9));
          Round(h, a, b, c, d, e, f, g, 0x78a5636f,
                w9 += sigma1(w7) + w2 + sigma0(w10));
          Round(g, h, a, b, c, d, e, f, 0x84c87814,
                w10 += sigma1(w8) + w3 + sigma0(w11));
          Round(f, g, h, a, b, c, d, e, 0x8cc70208,
                w11 += sigma1(w9) + w4 + sigma0(w12));
          Round(e, f, g, h, a, b, c, d, 0x90befffa,
                w12 += sigma1(w10) + w5 + sigma0(w13));
          Round(d, e, f, g, h, a, b, c, 0xa4506ceb,
                w13 += sigma1(w11) + w6 + sigma0(w14));
          Round(c, d, e, f, g, h, a, b, 0xbef9a3f7,
                w14 + sigma1(w12) + w7 + sigma0(w15));
          Round(b, c, d, e, f, g, h, a, 0xc67178f2,
                w15 + sigma1(w13) + w8 + sigma0(w0));
  
          s[0] += a;
          s[1] += b;
          s[2] += c;
          s[3] += d;
          s[4] += e;
          s[5] += f;
          s[6] += g;
          s[7] += h;
      }
  
  } // namespace sha256
  } // namespace
  
  ////// SHA-256
  
  CSHA256::CSHA256() : bytes(0) {
      sha256::Initialize(s);
  }
  
  CSHA256 &CSHA256::Write(const uint8_t *data, size_t len) {
      const uint8_t *end = data + len;
      size_t bufsize = bytes % 64;
      if (bufsize && bufsize + len >= 64) {
          // Fill the buffer, and process it.
          memcpy(buf + bufsize, data, 64 - bufsize);
          bytes += 64 - bufsize;
          data += 64 - bufsize;
          sha256::Transform(s, buf);
          bufsize = 0;
      }
      while (end >= data + 64) {
          // Process full chunks directly from the source.
          sha256::Transform(s, data);
          bytes += 64;
          data += 64;
      }
      if (end > data) {
          // Fill the buffer with what remains.
          memcpy(buf + bufsize, data, end - data);
          bytes += end - data;
      }
      return *this;
  }
  
  void CSHA256::Finalize(uint8_t hash[OUTPUT_SIZE]) {
      static const uint8_t pad[64] = {0x80};
      uint8_t sizedesc[8];
      WriteBE64(sizedesc, bytes << 3);
      Write(pad, 1 + ((119 - (bytes % 64)) % 64));
      Write(sizedesc, 8);
      WriteBE32(hash, s[0]);
      WriteBE32(hash + 4, s[1]);
      WriteBE32(hash + 8, s[2]);
      WriteBE32(hash + 12, s[3]);
      WriteBE32(hash + 16, s[4]);
      WriteBE32(hash + 20, s[5]);
      WriteBE32(hash + 24, s[6]);
      WriteBE32(hash + 28, s[7]);
  }
  
  CSHA256 &CSHA256::Reset() {
      bytes = 0;
      sha256::Initialize(s);
      return *this;
  }
  