crypto.sha256

/** FIPS 180-4 section 4.2.2: the first 32 bits of the fractional parts of the cube roots of the first 64 primes. */
const K = new Int32Array([
  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,
]);

/** FIPS 180-4 section 5.3.3: the initial hash value. */
const H0 = [0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19];

/**
 * The SHA-256 digest of a byte string (FIPS 180-4).
 *
 * Pure code, synchronous, with no node:crypto or crypto.subtle, so the same
 * function runs in the browser and on the server. Arithmetic is on signed
 * 32-bit integers (`| 0`), which wrap exactly as the standard's mod 2^32
 * additions require.
 */
export function sha256(bytes: readonly number[]): readonly number[] {
  if (!Array.isArray(bytes) && !(bytes instanceof Uint8Array)) {
    throw new TypeError("bytes must be a list of integers from 0 to 255");
  }
  const length = bytes.length;
  for (let i = 0; i < length; i++) {
    const b = bytes[i];
    if (typeof b !== "number" || !Number.isInteger(b) || b < 0 || b > 255) {
      throw new RangeError("bytes must be a list of integers from 0 to 255");
    }
  }

  // Padding (section 5.1.1): a 1 bit, zeros, then the length in bits as a
  // 64-bit big-endian integer, to a multiple of 64 bytes.
  const blocks = Math.floor((length + 8) / 64) + 1;
  const padded = new Uint8Array(blocks * 64);
  for (let i = 0; i < length; i++) padded[i] = bytes[i];
  padded[length] = 0x80;
  const bitsHigh = Math.floor(length / 0x20000000); // length * 8 / 2^32
  const bitsLow = (length * 8) >>> 0;
  const end = padded.length;
  padded[end - 8] = bitsHigh >>> 24;
  padded[end - 7] = (bitsHigh >>> 16) & 255;
  padded[end - 6] = (bitsHigh >>> 8) & 255;
  padded[end - 5] = bitsHigh & 255;
  padded[end - 4] = bitsLow >>> 24;
  padded[end - 3] = (bitsLow >>> 16) & 255;
  padded[end - 2] = (bitsLow >>> 8) & 255;
  padded[end - 1] = bitsLow & 255;

  const h = new Int32Array(H0);
  const w = new Int32Array(64);
  for (let block = 0; block < blocks; block++) {
    const base = block * 64;
    for (let t = 0; t < 16; t++) {
      const j = base + t * 4;
      w[t] = (padded[j] << 24) | (padded[j + 1] << 16) | (padded[j + 2] << 8) | padded[j + 3];
    }
    for (let t = 16; t < 64; t++) {
      const x = w[t - 15];
      const y = w[t - 2];
      const s0 = ((x >>> 7) | (x << 25)) ^ ((x >>> 18) | (x << 14)) ^ (x >>> 3);
      const s1 = ((y >>> 17) | (y << 15)) ^ ((y >>> 19) | (y << 13)) ^ (y >>> 10);
      w[t] = (w[t - 16] + s0 + w[t - 7] + s1) | 0;
    }
    let a = h[0], b = h[1], c = h[2], d = h[3], e = h[4], f = h[5], g = h[6], hh = h[7];
    for (let t = 0; t < 64; t++) {
      const S1 = ((e >>> 6) | (e << 26)) ^ ((e >>> 11) | (e << 21)) ^ ((e >>> 25) | (e << 7));
      const ch = (e & f) ^ (~e & g);
      const t1 = (hh + S1 + ch + K[t] + w[t]) | 0;
      const S0 = ((a >>> 2) | (a << 30)) ^ ((a >>> 13) | (a << 19)) ^ ((a >>> 22) | (a << 10));
      const maj = (a & b) ^ (a & c) ^ (b & c);
      const t2 = (S0 + maj) | 0;
      hh = g;
      g = f;
      f = e;
      e = (d + t1) | 0;
      d = c;
      c = b;
      b = a;
      a = (t1 + t2) | 0;
    }
    h[0] = (h[0] + a) | 0;
    h[1] = (h[1] + b) | 0;
    h[2] = (h[2] + c) | 0;
    h[3] = (h[3] + d) | 0;
    h[4] = (h[4] + e) | 0;
    h[5] = (h[5] + f) | 0;
    h[6] = (h[6] + g) | 0;
    h[7] = (h[7] + hh) | 0;
  }

  const out: number[] = [];
  for (let i = 0; i < 8; i++) {
    out.push((h[i] >>> 24) & 255, (h[i] >>> 16) & 255, (h[i] >>> 8) & 255, h[i] & 255);
  }
  return out;
}