sha1.js

/**
 * @file This is a SHA-1 hash generator by JavaScript.
 * @author Hsun
 * @description For your convenience, the code comments have been translated by Google.
 ***/

// 消息填充位，补足长度。
// Message padding bits, complement the length.
function fillString(str) {
  var blockAmount = ((str.length + 8) >> 6) + 1,
    blocks = [],
    i;

  for (i = 0; i < blockAmount * 16; i++) {
    blocks[i] = 0;
  }
  for (i = 0; i < str.length; i++) {
    blocks[i >> 2] |= str.charCodeAt(i) << (24 - (i & 3) * 8);
  }
  blocks[i >> 2] |= 0x80 << (24 - (i & 3) * 8);
  blocks[blockAmount * 16 - 1] = str.length * 8;

  return blocks;
}

// 将输入的二进制数组转化为十六进制的字符串。
// Convert the input binary array to a hexadecimal string.
function binToHex(binArray) {
  var hexString = "0123456789abcdef",
    str = "",
    i;

  for (i = 0; i < binArray.length * 4; i++) {
    str += hexString.charAt((binArray[i >> 2] >> ((3 - i % 4) * 8 + 4)) & 0xF) +
      hexString.charAt((binArray[i >> 2] >> ((3 - i % 4) * 8)) & 0xF);
  }

  return str;
}

// 核心函数，输出为长度为5的number数组，对应160位的消息摘要。
// The core function, the output is a number array with a length of 5,
// corresponding to a 160-bit message digest.
function core(blockArray) {
  var w = [],
    a = 0x67452301,
    b = 0xEFCDAB89,
    c = 0x98BADCFE,
    d = 0x10325476,
    e = 0xC3D2E1F0,
    olda,
    oldb,
    oldc,
    oldd,
    olde,
    t,
    i,
    j;

  for (i = 0; i < blockArray.length; i += 16) {  //每次处理512位 16*32
    olda = a;
    oldb = b;
    oldc = c;
    oldd = d;
    olde = e;

    for (j = 0; j < 80; j++) {  //对每个512位进行80步操作
      if (j < 16) {
        w[j] = blockArray[i + j];
      } else {
        w[j] = cyclicShift(w[j - 3] ^ w[j - 8] ^ w[j - 14] ^ w[j - 16], 1);
      }
      t = modPlus(modPlus(cyclicShift(a, 5), ft(j, b, c, d)), modPlus(modPlus(e, w[j]), kt(j)));
      e = d;
      d = c;
      c = cyclicShift(b, 30);
      b = a;
      a = t;
    }

    a = modPlus(a, olda);
    b = modPlus(b, oldb);
    c = modPlus(c, oldc);
    d = modPlus(d, oldd);
    e = modPlus(e, olde);
  }

  return [a, b, c, d, e];
}

// 根据t值返回相应得压缩函数中用到的f函数。
// According to the t value, return the corresponding f function used in
// the compression function.
function ft(t, b, c, d) {
  if (t < 20) {
    return (b & c) | ((~b) & d);
  } else if (t < 40) {
    return b ^ c ^ d;
  } else if (t < 60) {
    return (b & c) | (b & d) | (c & d);
  } else {
    return b ^ c ^ d;
  }
}

// 根据t值返回相应得压缩函数中用到的K值。
// According to the t value, return the corresponding K value used in
// the compression function.
function kt(t) {
  return (t < 20) ? 0x5A827999 :
    (t < 40) ? 0x6ED9EBA1 :
      (t < 60) ? 0x8F1BBCDC : 0xCA62C1D6;
}

// 模2的32次方加法，因为JavaScript的number是双精度浮点数表示，所以将32位数拆成高16位和低16位分别进行相加
// Modulo 2 to the 32nd power addition, because JavaScript's number is a
// double-precision floating-point number, so the 32-bit number is split
// into the upper 16 bits and the lower 16 bits are added separately.
function modPlus(x, y) {
  var low = (x & 0xFFFF) + (y & 0xFFFF),
    high = (x >> 16) + (y >> 16) + (low >> 16);

  return (high << 16) | (low & 0xFFFF);
}

// 对输入的32位的num二进制数进行循环左移 ,因为JavaScript的number是双精度浮点数表示，所以移位需需要注意
// Rotate left of the input 32-bit num binary number, because JavaScript's
// number is a double-precision floating-point number, so you need to pay
//  attention to the shift.
function cyclicShift(num, k) {
  return (num << k) | (num >>> (32 - k));
}

// 主函数根据输入的消息字符串计算消息摘要，返回十六进制表示的消息摘要
// The main function calculates the message digest based on the input message
// string and returns the message digest in hexadecimal.
export default function sha1(s) {
  return binToHex(core(fillString(s)));
}