/*!
 * utils.js - utils for bcoin
 * Copyright (c) 2014-2015, Fedor Indutny (MIT License)
 * Copyright (c) 2014-2016, Christopher Jeffrey (MIT License).
 * https://github.com/bcoin-org/bcoin
 */

'use strict';

/* global gc */

/**
 * @exports utils
 */

var utils = exports;

var assert = require('assert');
var bn = require('bn.js');
var util = require('util');
var crypto, supersha, hash, aes;

/**
 * Whether we're in a browser or not.
 * @const {Boolean}
 */

utils.isBrowser =
  (typeof process !== 'undefined' && process.browser)
  || typeof window !== 'undefined';

if (!utils.isBrowser) {
  crypto = require('cry' + 'pto');
  try {
    supersha = require('super' + 'sha');
  } catch (e) {
    ;
  }
} else {
  hash = require('hash.js');
  aes = require('./aes');
}

/**
 * The home directory.
 * @const {String}
 */

try {
  utils.HOME = require('o' + 's').homedir();
} catch (e) {
  utils.HOME = process.env.HOME
    || process.env.USERPROFILE
    || process.env.HOMEPATH
    || '/';
}

/**
 * Global NOP function.
 * @type function
 * @static
 * @method
 */

utils.nop = function() {};

/**
 * Garbage collector for `--expose-gc`.
 * @type function
 * @static
 * @method
 */

utils.gc = !utils.isBrowser && typeof gc === 'function' ? gc : utils.nop;

/**
 * Clone a buffer.
 * @param {Buffer} data
 * @returns {Buffer}
 */

utils.copy = function copy(data) {
  var clone = new Buffer(data.length);
  data.copy(clone, 0, 0, data.length);
  return clone;
};

/*
 * Base58
 */

var base58 = ''
  + '123456789'
  + 'ABCDEFGHJKLMNPQRSTUVWXYZ'
  + 'abcdefghijkmnopqrstuvwxyz';

var unbase58 = {};

for (var i = 0; i < base58.length; i++)
  unbase58[base58[i]] = i;

/**
 * Encode a base58 string.
 * @see https://github.com/bitcoin/bitcoin/blob/master/src/base58.cpp
 * @param {Buffer} data
 * @returns {Base58String}
 */

utils.toBase58 = function toBase58(data) {
  var zeroes = 0;
  var length = 0;
  var str = '';
  var i, b58, carry, j, k;

  for (i = 0; i < data.length; i++) {
    if (data[i] !== 0)
      break;
    zeroes++;
  }

  b58 = new Buffer(((data.length * 138 / 100) | 0) + 1);
  b58.fill(0);

  for (; i < data.length; i++) {
    carry = data[i];
    j = 0;
    for (k = b58.length - 1; k >= 0; k--, j++) {
      if (carry === 0 && j >= length)
        break;
      carry += 256 * b58[k];
      b58[k] = carry % 58;
      carry = carry / 58 | 0;
    }
    assert(carry === 0);
    length = j;
  }

  i = b58.length - length;
  while (i < b58.length && b58[i] === 0)
    i++;

  for (j = 0; j < zeroes; j++)
    str += '1';

  for (; i < b58.length; i++)
    str += base58[b58[i]];

  return str;
};

/**
 * Decode a base58 string.
 * @see https://github.com/bitcoin/bitcoin/blob/master/src/base58.cpp
 * @param {Base58String} str
 * @returns {Buffer}
 * @throws on non-base58 character.
 */

utils.fromBase58 = function fromBase58(str) {
  var zeroes = 0;
  var i = 0;
  var b256, ch, carry, j, out;

  for (i = 0; i < str.length; i++) {
    if (str[i] !== '1')
      break;
    zeroes++;
  }

  b256 = new Buffer(((str.length * 733) / 1000 | 0) + 1);
  b256.fill(0);

  for (; i < str.length; i++) {
    ch = unbase58[str[i]];
    if (ch == null)
      throw new Error('Non-base58 character.');

    carry = ch;
    for (j = b256.length - 1; j >= 0; j--) {
      carry += 58 * b256[j];
      b256[j] = carry % 256;
      carry = carry / 256 | 0;
    }

    assert(carry === 0);
  }

  i = 0;
  while (i < b256.length && b256[i] === 0)
    i++;

  out = new Buffer(zeroes + (b256.length - i));

  for (j = 0; j < zeroes; j++)
    out[j] = 0;

  while (i < b256.length)
    out[j++] = b256[i++];

  return out;
};

/**
 * Test whether a string is base58 (note that you
 * may get a false positive on a hex string).
 * @param {String?} obj
 * @returns {Boolean}
 */

utils.isBase58 = function isBase58(obj) {
  return typeof obj === 'string' && /^[1-9a-zA-Z]+$/.test(obj);
};

/**
 * Hash with chosen algorithm.
 * @param {String} alg
 * @param {Buffer|String} data
 * @param {String?} enc - Any buffer-supported encoding.
 * @returns {Buffer}
 */

utils.hash = function _hash(alg, data, enc) {
  if (!crypto)
    return new Buffer(hash[alg]().update(data, enc).digest());

  return crypto.createHash(alg).update(data, enc).digest();
};

/**
 * Hash with ripemd160.
 * @param {Buffer|String} data
 * @param {String?} enc - Any buffer-supported encoding.
 * @returns {Buffer}
 */

utils.ripemd160 = function ripemd160(data, enc) {
  return utils.hash('ripemd160', data, enc);
};

/**
 * Hash with sha1.
 * @param {Buffer|String} data
 * @param {String?} enc - Any buffer-supported encoding.
 * @returns {Buffer}
 */

utils.sha1 = function sha1(data, enc) {
  return utils.hash('sha1', data, enc);
};

/**
 * Hash with sha256.
 * @param {Buffer|String} data
 * @param {String?} enc - Any buffer-supported encoding.
 * @returns {Buffer}
 */

utils.sha256 = function sha256(data, enc) {
  if (supersha) {
    if (!Buffer.isBuffer(data))
      data = new Buffer(data, enc);
    return supersha.sha256(data);
  }
  return utils.hash('sha256', data, enc);
};

/**
 * Hash with sha256 and ripemd160 (OP_HASH160).
 * @param {Buffer|String} data
 * @param {String?} enc - Any buffer-supported encoding.
 * @returns {Buffer}
 */

utils.ripesha = function ripesha(data, enc) {
  return utils.ripemd160(utils.sha256(data, enc));
};

/**
 * Hash with sha256 twice (OP_HASH256).
 * @param {Buffer|String} data
 * @param {String?} enc - Any buffer-supported encoding.
 * @returns {Buffer}
 */

utils.dsha256 = function dsha256(data, enc) {
  if (supersha) {
    if (!Buffer.isBuffer(data))
      data = new Buffer(data, enc);
    return supersha.dsha256(data);
  }
  return utils.sha256(utils.sha256(data, enc));
};

/**
 * Create a sha256 checksum (common in bitcoin).
 * @param {Buffer|String} data
 * @param {String?} enc - Any buffer-supported encoding.
 * @returns {Buffer}
 */

utils.checksum = function checksum(data, enc) {
  return utils.dsha256(data, enc).slice(0, 4);
};

/**
 * Create an HMAC.
 * @param {String} alg
 * @param {Buffer} data
 * @param {Buffer} salt
 * @returns {Buffer} HMAC
 */

utils.hmac = function hmac(alg, data, salt) {
  var hmac;

  if (!crypto) {
    hmac = hash.hmac(hash[alg], salt);
    return new Buffer(hmac.update(data).digest());
  }

  hmac = crypto.createHmac(alg, salt);
  return hmac.update(data).digest();
};

/**
 * Perform key stretching using PBKDF2.
 * @param {Buffer} key
 * @param {Buffer} salt
 * @param {Number} iterations
 * @param {Number} dkLen - Output size.
 * @param {String?} alg
 */

/*!
 * PBKDF2
 * Credit to: https://github.com/stayradiated/pbkdf2-sha512
 * Copyright (c) 2010-2011 Intalio Pte, All Rights Reserved
 * Copyright (c) 2014, JP Richardson
 */

utils.pbkdf2 = function pbkdf2(key, salt, iterations, dkLen, alg) {
  var hLen, DK, U, T, block, l, r;
  var i, j, k, destPos, len;

  if (typeof key === 'string')
    key = new Buffer(key, 'utf8');

  if (typeof salt === 'string')
    salt = new Buffer(salt, 'utf8');

  if (!alg)
    alg = 'sha512';

  if (crypto && crypto.pbkdf2Sync)
    return crypto.pbkdf2Sync(key, salt, iterations, dkLen, alg);

  if (alg === 'sha512')
    hLen = 64;
  else if (alg === 'sha256')
    hLen = 32;
  else if (alg === 'sha1' || alg === 'ripemd160')
    hLen = 20;
  else if (alg === 'md5')
    hLen = 16;

  assert(dkLen <= 0xffffffff * hLen, 'Requested key length too long');

  DK = new Buffer(dkLen);
  T = new Buffer(hLen);
  block = new Buffer(salt.length + 4);

  l = Math.ceil(dkLen / hLen);
  r = dkLen - (l - 1) * hLen;

  salt.copy(block, 0, 0, salt.length);

  for (i = 1; i <= l; i++) {
    block[salt.length + 0] = (i >>> 24) & 0xff;
    block[salt.length + 1] = (i >>> 16) & 0xff;
    block[salt.length + 2] = (i >>> 8) & 0xff;
    block[salt.length + 3] = (i >>> 0) & 0xff;

    U = utils.hmac(alg, block, key);

    U.copy(T, 0, 0, hLen);

    for (j = 1; j < iterations; j++) {
      U = utils.hmac(alg, U, key);

      for (k = 0; k < hLen; k++)
        T[k] ^= U[k];
    }

    destPos = (i - 1) * hLen;
    len = i === l ? r : hLen;
    T.copy(DK, destPos, 0, len);
  }

  return DK;
};

/**
 * Encrypt with aes-256-cbc.
 * @param {Buffer|String} data
 * @param {Buffer|String} passphrase
 * @returns {Buffer}
 */

utils.encrypt = function encrypt(data, passphrase) {
  var key, cipher, out;

  assert(passphrase, 'No passphrase.');

  if (typeof data === 'string')
    data = new Buffer(data, 'utf8');

  if (typeof passphrase === 'string')
    passphrase = new Buffer(passphrase, 'utf8');

  key = utils.pbkdf2key(passphrase, 2048, 32, 16);

  if (!crypto) {
    out = aes.cbc.encrypt(data, key.key, key.iv);
    key.key.fill(0);
    key.iv.fill(0);
    return out;
  }

  cipher = crypto.createCipheriv('aes-256-cbc', key.key, key.iv);

  out = Buffer.concat([
    cipher.update(data),
    cipher.final()
  ]);

  key.key.fill(0);
  key.iv.fill(0);

  return out;
};

/**
 * Decrypt from aes-256-cbc.
 * @param {Buffer|String} data
 * @param {Buffer|String} passphrase
 * @returns {Buffer}
 */

utils.decrypt = function decrypt(data, passphrase) {
  var key, decipher, out;

  assert(passphrase, 'No passphrase.');

  if (typeof data === 'string')
    data = new Buffer(data, 'hex');

  if (typeof passphrase === 'string')
    passphrase = new Buffer(passphrase, 'utf8');

  key = utils.pbkdf2key(passphrase, 2048, 32, 16);

  if (!crypto) {
    out = aes.cbc.decrypt(data, key.key, key.iv);
    key.key.fill(0);
    key.iv.fill(0);
    return out;
  }

  decipher = crypto.createDecipheriv('aes-256-cbc', key.key, key.iv);

  out = Buffer.concat([
    decipher.update(data),
    decipher.final()
  ]);

  key.key.fill(0);
  key.iv.fill(0);

  return out;
};

/**
 * Generate a key and IV using pbkdf2.
 * @param {Buffer|String} passphrase
 * @param {(Buffer|String)?} salt
 * @param {Number} iterations
 * @param {Number} dkLen
 * @param {Number} ivLen
 * @param {String?} alg
 * @returns {Buffer}
 */

utils.pbkdf2key = function pbkdf2key(passphrase, iterations, dkLen, ivLen, alg) {
  var key = utils.pbkdf2(passphrase, '', iterations, dkLen + ivLen, alg);
  return {
    key: key.slice(0, dkLen),
    iv: key.slice(dkLen, dkLen + ivLen)
  };
};

/**
 * Test whether a string is hex. Note that this
 * _could_ yield a false positive on base58
 * strings.
 * @param {String?} obj
 * @returns {Boolean}
 */

utils.isHex = function isHex(obj) {
  return typeof obj === 'string'
    && /^[0-9a-f]+$/i.test(obj)
    && obj.length % 2 === 0;
};

/**
 * Test whether two buffers are equal.
 * @param {Buffer?} a
 * @param {Buffer?} b
 * @returns {Boolean}
 */

utils.equal = function equal(a, b) {
  var i;

  if (!Buffer.isBuffer(a))
    return false;

  if (!Buffer.isBuffer(b))
    return false;

  if (a.compare)
    return a.compare(b) === 0;

  if (a.length !== b.length)
    return false;

  for (i = 0; i < a.length; i++) {
    if (a[i] !== b[i])
      return false;
  }

  return true;
};

/**
 * Call `setImmediate`, `process.nextTick`,
 * or `setInterval` depending.
 * @name nextTick
 * @function
 * @param {Function} callback
 */

if (utils.isBrowser)
  require('../../vendor/setimmediate');

if (typeof setImmediate === 'function') {
  utils.nextTick = setImmediate;
} else if (!utils.isBrowser) {
  utils.nextTick = process.nextTick;
} else {
  utils.nextTick = function nextTick(fn) {
    setTimeout(fn, 1);
  };
}

/**
 * Wrap a function in a `nextTick`.
 * @param {Function} callback
 * @returns {Function} Asyncified function.
 */

utils.asyncify = function asyncify(callback) {
  if (callback && callback._asyncified)
    return callback;

  function asyncifyFn(err, result1, result2) {
    if (!callback)
      return;
    utils.nextTick(function() {
      callback(err, result1, result2);
    });
  }

  asyncifyFn._asyncified = true;
  if (callback)
    asyncifyFn._once = callback._once;

  return asyncifyFn;
};

/**
 * Ensure a callback exists, return a NOP if not.
 * @param {Function} callback
 * @returns {Function}
 */

utils.ensure = function ensure(callback) {
  if (!callback)
    return utils.nop;
  return callback;
};

/**
 * Reverse a hex-string (used because of
 * bitcoind's affinity for uint256le).
 * @param {String} s - Hex string.
 * @returns {String} Reversed hex string.
 */

utils.revHex = function revHex(s) {
  var r = '';
  var i = 0;

  for (; i < s.length; i += 2)
    r = s.slice(i, i + 2) + r;

  return r;
};

/**
 * Shallow merge between multiple objects.
 * @param {Object} target
 * @param {...Object} args
 * @returns {Object} target
 */

utils.merge = function merge(target) {
  var i, j, obj, keys, key;

  for (i = 1; i < arguments.length; i++) {
    obj = arguments[i];
    keys = Object.keys(obj);
    for (j = 0; j < keys.length; j++) {
      key = keys[j];
      target[key] = obj[key];
    }
  }

  return target;
};

/**
 * Assertion.
 * @param {Boolean} value - Expression.
 * @param {String?} message - Optional error message.
 */

utils.assert = function _assert(value, message) {
  if (!value) {
    throw new assert.AssertionError({
      message: message,
      actual: value,
      expected: true,
      operator: '==',
      stackStartFunction: _assert
    });
  }
};

utils.merge(utils.assert, assert);

utils.assert.fatal = function fatal(value, message) {
  var err;

  if (!value) {
    if (!message)
      message = 'Assertion failed (fatal exception)';

    err = new assert.AssertionError({
      message: message,
      actual: value,
      expected: true,
      operator: '==',
      stackStartFunction: fatal
    });

    if (process.exit) {
      console.error(err.stack + '');
      process.exit(1);
    } else {
      throw err;
    }
  }
};

/**
 * Safely convert satoshis to a BTC string.
 * This function explicitly avoids any
 * floating point arithmetic.
 * @param {Amount} value - Satoshis.
 * @returns {String} BTC string.
 */

utils.btc = function btc(value) {
  var negative = false;
  var hi, lo, result;

  if (utils.isFloat(value))
    return value;

  assert(utils.isInt(value), 'Non-satoshi value for conversion.');

  if (value < 0) {
    value = -value;
    negative = true;
  }

  assert(value <= utils.MAX_SAFE_INTEGER, 'Number exceeds 2^53-1.');

  value = value.toString(10);

  assert(value.length <= 16, 'Number exceeds 2^53-1.');

  while (value.length < 9)
    value = '0' + value;

  hi = value.slice(0, -8);
  lo = value.slice(-8);

  lo = lo.replace(/0+$/, '');

  if (lo.length === 0)
    lo += '0';

  result = hi + '.' + lo;

  if (negative)
    result = '-' + result;

  return result;
};

/**
 * Safely convert a BTC string to satoshis.
 * This function explicitly avoids any
 * floating point arithmetic. It also does
 * extra validation to ensure the resulting
 * Number will be 53 bits or less.
 * @param {String} value - BTC
 * @returns {Amount} Satoshis.
 * @throws on parse error
 */

utils.satoshi = function satoshi(value) {
  var negative = false;
  var parts, hi, lo, result;

  if (utils.isInt(value))
    return value;

  assert(utils.isFloat(value), 'Non-BTC value for conversion.');

  if (value[0] === '-') {
    negative = true;
    value = value.substring(1);
  }

  parts = value.split('.');

  assert(parts.length <= 2, 'Bad decimal point.');

  hi = parts[0] || '0';
  lo = parts[1] || '0';

  hi = hi.replace(/^0+/, '');
  lo = lo.replace(/0+$/, '');

  assert(hi.length <= 8, 'Number exceeds 2^53-1.');
  assert(lo.length <= 8, 'Too many decimal places.');

  if (hi.length === 0)
    hi = '0';

  while (lo.length < 8)
    lo += '0';

  hi = parseInt(hi, 10);
  lo = parseInt(lo, 10);

  assert(hi < 90071992 || (hi === 90071992 && lo <= 54740991),
    'Number exceeds 2^53-1.');

  result = hi * 100000000 + lo;

  if (negative)
    result = -result;

  return result;
};

/**
 * Test whether a number is both a Number and finite.
 * @param {Number?} value
 * @returns {Boolean}
 */

utils.isNumber = function isNumber(value) {
  return typeof value === 'number' && isFinite(value);
};

/**
 * Test whether a string qualifies as a float.
 * @param {String?} value
 * @returns {Boolean}
 */

utils.isFloat = function isFloat(value) {
  return typeof value === 'string'
    && /^-?(\d+)?(?:\.\d*)?$/.test(value)
    && value.length !== 0
    && value !== '-';
};

/**
 * Test whether an object is a finite number and int.
 * @param {Number?} value
 * @returns {Boolean}
 */

utils.isInt = function isInt(value) {
  return utils.isNumber(value) && value % 1 === 0;
};

/**
 * Test and validate a satoshi value (Number).
 * @param {Number?} value
 * @returns {Boolean}
 */

utils.isSatoshi = function isSatoshi(value) {
  try {
    utils.satoshi(value);
    return true;
  } catch (e) {
    return false;
  }
};

/**
 * Test and validate a BTC string.
 * @param {String?} value
 * @returns {Boolean}
 */

utils.isBTC = function isBTC(value) {
  try {
    utils.btc(value);
    return true;
  } catch (e) {
    return false;
  }
};

/**
 * util.inspect() with 20 levels of depth.
 * @param {Object|String} obj
 * @param {Boolean?} color
 * @return {String}
 */

utils.inspectify = function inspectify(obj, color) {
  return typeof obj !== 'string'
    ? util.inspect(obj, null, 20, color !== false)
    : obj;
};

/**
 * Format a string.
 * @param {Array} args
 * @param {Boolean?} color
 * @return {String}
 */

utils.format = function format(args, color) {
  color = color
    ? (process.stdout ? process.stdout.isTTY : false)
    : false;

  return typeof args[0] === 'object'
    ? utils.inspectify(args[0], color)
    : util.format.apply(util, args);
};

/**
 * Write a message to stdout (console in browser).
 * @param {Object|String} obj
 * @param {...String} args
 */

utils.print = function print() {
  var args = new Array(arguments.length);
  var i, msg;

  for (i = 0; i < args.length; i++)
    args[i] = arguments[i];

  if (utils.isBrowser) {
    msg = typeof args[0] !== 'object'
      ? utils.format(args, false)
      : args[0];
    console.log(msg);
    return;
  }

  msg = utils.format(args, true);
  process.stdout.write(msg + '\n');
};

/**
 * Write a message to stderr (console in browser).
 * @param {Object|String} obj
 * @param {...String} args
 */

utils.error = function error() {
  var args = new Array(arguments.length);
  var i, msg;

  for (i = 0; i < args.length; i++)
    args[i] = arguments[i];

  if (utils.isBrowser) {
    msg = typeof args[0] !== 'object'
      ? utils.format(args, false)
      : args[0];
    console.log(msg);
    return;
  }

  msg = utils.format(args, true);
  process.stderr.write(msg + '\n');
};

/**
 * Sort public keys lexicographically.
 * @param {Buffer[]} keys
 * @returns {Buffer[]} Sorted keys.
 */

utils.sortKeys = function sortKeys(keys) {
  return keys.slice().sort(function(a, b) {
    return utils.cmp(a, b);
  });
};

/**
 * Sort HD public keys lexicographically.
 * @param {HDPublicKey[]} keys
 * @returns {HDPublicKey[]} Sorted keys.
 */

utils.sortHDKeys = function sortHDKeys(keys) {
  return keys.slice().sort(function(a, b) {
    return utils.cmp(a.publicKey, b.publicKey);
  });
};

/**
 * Sort transactions by timestamp.
 * @param {TX[]} txs
 * @returns {TX[]} Sorted transactions.
 */

utils.sortTX = function sortTX(txs) {
  return txs.slice().sort(function(a, b) {
    a = a.ts || a.ps;
    b = b.ts || b.ps;
    return a - b;
  });
};

/**
 * Unique-ify an array of strings.
 * @param {String[]} obj
 * @returns {String[]}
 */

utils.uniq = function uniq(obj) {
  var table = {};
  var out = [];
  var i = 0;

  for (; i < obj.length; i++) {
    if (!table[obj[i]]) {
      out.push(obj[i]);
      table[obj[i]] = true;
    }
  }

  return out;
};

/**
 * Convert a compact number to a big number.
 * Used for `block.bits` -> `target` conversion.
 * @param {Number} compact
 * @returns {BN}
 */

utils.fromCompact = function fromCompact(compact) {
  var exponent = compact >>> 24;
  var negative = (compact >>> 23) & 1;
  var mantissa = compact & 0x7fffff;
  var num;

  if (compact === 0)
    return new bn(0);

  // Logic ported from btcd since
  // the bitcoind code is a nightmare.
  if (exponent <= 3) {
    mantissa >>>= 8 * (3 - exponent);
    num = new bn(mantissa);
  } else {
    num = new bn(mantissa);
    num.iushln(8 * (exponent - 3));
  }

  if (negative)
    num.ineg();

  return num;
};

/**
 * Convert a big number to a compact number.
 * Used for `target` -> `block.bits` conversion.
 * @param {BN} num
 * @returns {Number}
 */

utils.toCompact = function toCompact(num) {
  var mantissa, exponent, compact;

  if (num.cmpn(0) === 0)
    return 0;

  exponent = num.byteLength();

  // Logic ported from btcd since
  // the bitcoind code is a nightmare.
  if (exponent <= 3) {
    mantissa = num.toNumber();
    mantissa <<= 8 * (3 - exponent);
  } else {
    mantissa = num.ushrn(8 * (exponent - 3)).toNumber();
  }

  if (mantissa & 0x800000) {
    mantissa >>= 8;
    exponent++;
  }

  compact = (exponent << 24) | mantissa;

  if (num.isNeg())
    compact |= 0x800000;

  compact >>>= 0;

  return compact;
};

/**
 * Test hash against a target.
 * @param {Buffer|Hash} hash
 * @param {BN|Number} target - Compact number or big number.
 * @returns {Boolean} True if hash is less than target.
 */

utils.testTarget = function testTarget(hash, target) {
  if (typeof hash === 'string')
    hash = new Buffer(hash, 'hex');

  if (typeof target === 'number')
    target = utils.fromCompact(target);

  if (target.isNeg() || target.cmpn(0) === 0)
    return false;

  hash = new bn(hash, 'le');

  if (hash.cmp(target) > 0)
    return false;

  return true;
};

/**
 * Get current time in unix time (seconds).
 * @returns {Number}
 */

utils.now = function now() {
  return Math.floor(+new Date() / 1000);
};

/**
 * Get current time in unix time (milliseconds).
 * @returns {Number}
 */

utils.ms = function ms() {
  return +new Date();
};

/**
 * Create a Date ISO string from time in unix time (seconds).
 * @param {Number?} ts - Seconds in unix time.
 * @returns {String}
 */

utils.date = function date(ts) {
  if (ts == null)
    ts = utils.now();

  return new Date(ts * 1000).toISOString().slice(0, -5) + 'Z';
};

/**
 * Get unix seconds from a Date string.
 * @param {String} date - Date ISO String.
 * @returns {Number}
 */

utils.time = function time(date) {
  if (date == null)
    return utils.now();

  return new Date(date) / 1000 | 0;
};

/**
 * UINT32_MAX
 * @const {BN}
 */

utils.U32 = new bn(0xffffffff);

/**
 * UINT64_MAX
 * @const {BN}
 */

utils.U64 = new bn('ffffffffffffffff', 'hex');

/**
 * Create an 8 byte nonce.
 * @returns {BN}
 */

utils.nonce = function _nonce() {
  var nonce = new Buffer(8);
  nonce.writeUInt32LE((Math.random() * 0x100000000) >>> 0, 0, true);
  nonce.writeUInt32LE((Math.random() * 0x100000000) >>> 0, 4, true);
  return new bn(nonce);
};

/**
 * Read uint64le.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {BN}
 */

utils.readU64 = function readU64(data, off) {
  var num;
  off = off >>> 0;
  num = data.slice(off, off + 8);
  return new bn(num, 'le');
};

/**
 * Read uint64be.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {BN}
 */

utils.readU64BE = function readU64BE(data, off) {
  var num;
  off = off >>> 0;
  num = data.slice(off, off + 8);
  return new bn(num, 'be');
};

/**
 * Read int64le.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {BN}
 */

utils.read64 = function read64(data, off) {
  var num;

  off = off >>> 0;

  num = data.slice(off, off + 8);

  if (num[num.length - 1] & 0x80)
    return new bn(num, 'le').notn(64).addn(1).neg();

  return new bn(num, 'le');
};

/**
 * Read int64be.
 * @param {Buffer} data
 * @param {Number} off
 * @returns {BN}
 */

utils.read64BE = function read64BE(data, off) {
  var num;

  off = off >>> 0;

  num = data.slice(off, off + 8);

  if (num[0] & 0x80)
    return new bn(num, 'be').notn(64).addn(1).neg();

  return new bn(num, 'be');
};

/**
 * Write uint64le.
 * @param {BN|Number} value
 */

utils.writeU64 = function writeU64(dst, num, off) {
  return utils.write64(dst, num, off);
};

/**
 * Write uint64be.
 * @param {BN|Number} value
 */

utils.writeU64BE = function writeU64BE(dst, num, off) {
  return utils.write64BE(dst, num, off);
};

/**
 * Write a javascript number as a uint64le (faster than big numbers).
 * @param {Number} value
 * @throws on num > MAX_SAFE_INTEGER
 */

utils.writeU64N = function writeU64N(dst, num, off) {
  return utils.write64N(dst, num, off);
};

/**
 * Write a javascript number as a uint64be (faster than big numbers).
 * @param {Number} value
 * @throws on num > MAX_SAFE_INTEGER
 */

utils.writeU64NBE = function writeU64NBE(dst, num, off) {
  return utils.write64NBE(dst, num, off);
};

/**
 * Max safe integer (53 bits).
 * @const {Number}
 * @default
 */

utils.MAX_SAFE_INTEGER = 0x1fffffffffffff;

/**
 * Max 52 bit integer (safe for additions).
 * `(MAX_SAFE_INTEGER - 1) / 2`
 * @const {Number}
 * @default
 */

utils.MAX_SAFE_ADDITION = 0xfffffffffffff;

/**
 * Write a javascript number as an int64le (faster than big numbers).
 * @param {Number} value
 * @throws on num > MAX_SAFE_INTEGER
 */

utils.write64N = function write64N(dst, num, off, be) {
  var negative, hi, lo;

  assert(typeof num === 'number');

  off = off >>> 0;

  negative = num < 0;

  if (negative) {
    num = -num;
    num -= 1;
  }

  assert(num <= utils.MAX_SAFE_INTEGER, 'Number exceeds 2^53-1');

  lo = num % 0x100000000;
  hi = (num - lo) / 0x100000000;

  if (negative) {
    hi = ~hi >>> 0;
    lo = ~lo >>> 0;
  }

  if (be) {
    dst[off + 0] = (hi >>> 24) & 0xff;
    dst[off + 1] = (hi >>> 16) & 0xff;
    dst[off + 2] = (hi >>> 8) & 0xff;
    dst[off + 3] = (hi >>> 0) & 0xff;
    dst[off + 4] = (lo >>> 24) & 0xff;
    dst[off + 5] = (lo >>> 16) & 0xff;
    dst[off + 6] = (lo >>> 8) & 0xff;
    dst[off + 7] = (lo >>> 0) & 0xff;
  } else {
    dst[off + 0] = (lo >>> 0) & 0xff;
    dst[off + 1] = (lo >>> 8) & 0xff;
    dst[off + 2] = (lo >>> 16) & 0xff;
    dst[off + 3] = (lo >>> 24) & 0xff;
    dst[off + 4] = (hi >>> 0) & 0xff;
    dst[off + 5] = (hi >>> 8) & 0xff;
    dst[off + 6] = (hi >>> 16) & 0xff;
    dst[off + 7] = (hi >>> 24) & 0xff;
  }

  return off + 8;
};

/**
 * Write a javascript number as an int64be (faster than big numbers).
 * @param {Number} value
 * @throws on num > MAX_SAFE_INTEGER
 */

utils.write64NBE = function write64NBE(dst, num, off) {
  return utils.write64N(dst, num, off, true);
};

/**
 * Read uint64le as a js number.
 * @param {Buffer} data
 * @param {Number} off
 * @param {Boolean} force53 - Read only 53 bits, but maintain the sign.
 * @returns {Number}
 * @throws on num > MAX_SAFE_INTEGER
 */

utils.readU64N = function readU64N(data, off, force53, be) {
  var hi, lo;

  off = off >>> 0;

  if (be) {
    hi = data.readUInt32BE(off, true);
    lo = data.readUInt32BE(off + 4, true);
  } else {
    hi = data.readUInt32LE(off + 4, true);
    lo = data.readUInt32LE(off, true);
  }

  if (force53)
    hi &= 0x1fffff;

  assert((hi & 0xffe00000) === 0, 'Number exceeds 2^53-1');

  return (hi * 0x100000000) + lo;
};

/**
 * Read uint64be as a js number.
 * @param {Buffer} data
 * @param {Number} off
 * @param {Boolean} force53 - Read only 53 bits, but maintain the sign.
 * @returns {Number}
 * @throws on num > MAX_SAFE_INTEGER
 */

utils.readU64NBE = function readU64NBE(data, off, force53) {
  return utils.readU64N(data, off, force53, true);
};

/**
 * Read int64le as a js number.
 * @param {Buffer} data
 * @param {Number} off
 * @param {Boolean} force53 - Read only 53 bits, but maintain the sign.
 * @returns {Number}
 * @throws on num > MAX_SAFE_INTEGER
 */

utils.read64N = function read64N(data, off, force53, be) {
  var hi, lo;

  off = off >>> 0;

  if (be) {
    hi = data.readUInt32BE(off, true);
    lo = data.readUInt32BE(off + 4, true);
  } else {
    hi = data.readUInt32LE(off + 4, true);
    lo = data.readUInt32LE(off, true);
  }

  if (hi & 0x80000000) {
    hi = ~hi >>> 0;
    lo = ~lo >>> 0;

    if (force53)
      hi &= 0x1fffff;

    assert((hi & 0xffe00000) === 0, 'Number exceeds 2^53-1');

    return -(hi * 0x100000000 + lo + 1);
  }

  if (force53)
    hi &= 0x1fffff;

  assert((hi & 0xffe00000) === 0, 'Number exceeds 2^53-1');

  return hi * 0x100000000 + lo;
};

/**
 * Read int64be as a js number.
 * @param {Buffer} data
 * @param {Number} off
 * @param {Boolean} force53 - Read only 53 bits, but maintain the sign.
 * @returns {Number}
 * @throws on num > MAX_SAFE_INTEGER
 */

utils.read64NBE = function read64NBE(data, off, force53) {
  return utils.read64N(data, off, force53, true);
};

/**
 * Write int64le.
 * @param {Buffer} dst
 * @param {BN|Number} num
 * @param {Number} off
 * @returns {Number} Number of bytes written.
 */

utils.write64 = function write64(dst, num, off) {
  var i;

  if (typeof num === 'number')
    return utils.write64N(dst, num, off);

  off = off >>> 0;

  if (num.isNeg())
    num = num.neg().inotn(64).iaddn(1);

  if (num.bitLength() > 64)
    num = num.uand(utils.U64);

  num = num.toArray('le', 8);

  for (i = 0; i < num.length; i++)
    dst[off++] = num[i];

  return off;
};

/**
 * Write int64be.
 * @param {Buffer} dst
 * @param {BN|Number} num
 * @param {Number} off
 * @returns {Number} Number of bytes written.
 */

utils.write64BE = function write64BE(dst, num, off) {
  var i;

  if (typeof num === 'number')
    return utils.write64NBE(dst, num, off);

  off = off >>> 0;

  if (num.isNeg())
    num = num.neg().inotn(64).iaddn(1);

  if (num.bitLength() > 64)
    num = num.uand(utils.U64);

  num = num.toArray('be', 8);

  for (i = 0; i < num.length; i++)
    dst[off++] = num[i];

  return off;
};

/**
 * Read a varint.
 * @param {Buffer} data
 * @param {Number} off
 * @param {Boolean?} big - Whether to read as a big number.
 * @returns {Object}
 */

utils.readVarint = function readVarint(data, off, big) {
  var value, size;

  off = off >>> 0;

  assert(off < data.length);

  if (data[off] < 0xfd) {
    size = 1;
    value = data[off];
    if (big)
      value = new bn(value);
  } else if (data[off] === 0xfd) {
    size = 3;
    assert(off + size <= data.length);
    value = data[off + 1] | (data[off + 2] << 8);
    assert(value >= 0xfd);
    if (big)
      value = new bn(value);
  } else if (data[off] === 0xfe) {
    size = 5;
    assert(off + size <= data.length);
    value = data.readUInt32LE(off + 1, true);
    assert(value > 0xffff);
    if (big)
      value = new bn(value);
  } else if (data[off] === 0xff) {
    size = 9;
    assert(off + size <= data.length);
    if (big) {
      value = utils.readU64(data, off + 1);
      assert(value.bitLength() > 32);
    } else {
      value = utils.readU64N(data, off + 1);
      assert(value > 0xffffffff);
    }
  } else {
    assert(false, 'Malformed varint.');
  }

  return { size: size, value: value };
};

/**
 * Write a varint.
 * @param {Buffer} dst
 * @param {BN|Number} num
 * @param {Number} off
 * @returns {Number} Number of bytes written.
 */

utils.writeVarint = function writeVarint(dst, num, off) {
  off = off >>> 0;

  if (bn.isBN(num)) {
    if (num.bitLength() > 32) {
      dst[off] = 0xff;
      utils.writeU64(dst, num, off + 1);
      return off + 9;
    }
    num = num.toNumber();
  }

  num = +num;

  if (num < 0xfd) {
    dst[off] = num & 0xff;
    return off + 1;
  }

  if (num <= 0xffff) {
    dst[off] = 0xfd;
    dst[off + 1] = num & 0xff;
    dst[off + 2] = (num >>> 8) & 0xff;
    return off + 3;
  }

  if (num <= 0xffffffff) {
    dst[off] = 0xfe;
    dst[off + 1] = num & 0xff;
    dst[off + 2] = (num >>> 8) & 0xff;
    dst[off + 3] = (num >>> 16) & 0xff;
    dst[off + 4] = (num >>> 24) & 0xff;
    return off + 5;
  }

  dst[off] = 0xff;
  utils.writeU64N(dst, num, off + 1);

  return off + 9;
};

/**
 * Calculate size of varint.
 * @param {BN|Number} num
 * @returns {Number} size
 */

utils.sizeVarint = function sizeVarint(num) {
  if (bn.isBN(num)) {
    if (num.bitLength() > 32)
      return 9;
    num = num.toNumber();
  }

  if (num < 0xfd)
    return 1;

  if (num <= 0xffff)
    return 3;

  if (num <= 0xffffffff)
    return 5;

  return 9;
};

/**
 * Read a varint (type 2).
 * @param {Buffer} data
 * @param {Number} off
 * @param {Boolean?} big - Whether to read as a big number.
 * @returns {Object}
 */

utils.readVarint2 = function readVarint2(data, off, big) {
  var num = 0;
  var size = 0;
  var bnum, ch;

  off = off >>> 0;

  for (;;) {
    assert(off < data.length);

    ch = data[off++];
    size++;

    if (num >= 0x3fffffffffff) {
      assert(big, 'Number exceeds 2^53-1.');
      bnum = new bn(num);
      num = 0;
    }

    if (bnum) {
      bnum.iushln(7).iaddn(ch & 0x7f);
      if ((ch & 0x80) === 0)
        break;
      bnum.iaddn(1);
      continue;
    }

    num = (num * 0x80) + (ch & 0x7f);
    if ((ch & 0x80) === 0)
      break;
    num++;
  }

  if (bnum)
    return { size: size, value: bnum };

  if (big)
    num = new bn(num);

  return { size: size, value: num };
};

/**
 * Write a varint (type 2).
 * @param {Buffer} dst
 * @param {BN|Number} num
 * @param {Number} off
 * @returns {Number} Number of bytes written.
 */

utils.writeVarint2 = function writeVarint2(dst, num, off) {
  var tmp = [];
  var len = 0;

  if (bn.isBN(num)) {
    if (num.bitLength() > 53) {
      for (;;) {
        tmp[len] = (num.words[0] & 0x7f) | (len ? 0x80 : 0x00);
        if (num.cmpn(0x7f) <= 0)
          break;
        num.iushrn(7).isubn(1);
        len++;
      }

      assert(off + len <= dst.length);

      do {
        dst[off++] = tmp[len];
      } while (len--);

      return off;
    }

    num = num.toNumber();
  }

  off = off >>> 0;
  num = +num;

  for (;;) {
    tmp[len] = (num & 0x7f) | (len ? 0x80 : 0x00);
    if (num <= 0x7f)
      break;
    num = ((num - (num % 0x80)) / 0x80) - 1;
    len++;
  }

  assert(off + len <= dst.length);

  do {
    dst[off++] = tmp[len];
  } while (len--);

  return off;
};

/**
 * Calculate size of varint (type 2).
 * @param {BN|Number} num
 * @returns {Number} size
 */

utils.sizeVarint2 = function sizeVarint2(num) {
  var size = 0;

  if (bn.isBN(num)) {
    if (num.bitLength() > 53) {
      num = num.clone();

      for (;;) {
        size++;
        if (num.cmpn(0x7f) <= 0)
          break;
        num.iushrn(7).isubn(1);
      }

      return size;
    }

    num = num.toNumber();
  }

  num = +num;

  for (;;) {
    size++;
    if (num <= 0x7f)
      break;
    num = ((num - (num % 0x80)) / 0x80) - 1;
  }

  return size;
};

/**
 * Buffer comparator (memcmp + length comparison).
 * @param {Buffer} a
 * @param {Buffer} b
 * @returns {Number} -1, 1, or 0.
 */

utils.cmp = function cmp(a, b) {
  var len, i;

  if (a.compare)
    return a.compare(b);

  len = Math.min(a.length, b.length);

  for (i = 0; i < len; i++) {
    if (a[i] < b[i])
      return -1;
    if (a[i] > b[i])
      return 1;
  }

  if (a.length < b.length)
    return -1;

  if (a.length > b.length)
    return 1;

  return 0;
};

/**
 * Memcmp for comparing a needle to a haystack.
 * @param {Buffer} target - Haystack.
 * @param {Buffer} data - Needle.
 * @param {Number} start - Index in haystack to begin the comparison.
 * @returns {Number} -1, 1, or 0.
 */

utils.icmp = function icmp(target, data, start) {
  var i, a, b;

  if (target.length - start < data.length)
    return -1;

  for (i = 0; i < data.length; i++) {
    a = target[i + start];
    b = data[i];
    if (a < b)
      return -1;
    if (a > b)
      return 1;
  }

  return 0;
};

/**
 * memcmp in constant time (can only return true or false).
 * This protects us against timing attacks when
 * comparing an input against a secret string.
 * @see https://cryptocoding.net/index.php/Coding_rules
 * @see `$ man 3 memcmp` (NetBSD's consttime_memequal)
 * @param {Buffer} a
 * @param {Buffer} b
 * @returns {Boolean}
 */

utils.ccmp = function ccmp(a, b) {
  var res = 0;
  var i;

  if (!Buffer.isBuffer(a))
    return false;

  if (!Buffer.isBuffer(b))
    return false;

  for (i = 0; i < a.length; i++)
    res |= a[i] ^ b[i];

  return res === 0;
};

/**
 * Asnchronously iterate over a range in parallel.
 * @param {Number} from
 * @param {Number} to
 * @param {Function} iter
 * @param {Function} callback
 */

utils.forRange = function forRange(from, to, iter, callback) {
  var pending = to - from;
  var i, error;

  callback = utils.asyncify(callback);

  if (pending <= 0)
    return callback();

  function next(err) {
    assert(pending > 0);
    if (err)
      error = err;
    if (!--pending)
      callback(error);
  }

  for (i = from; i < to; i++)
    iter(i, next, i);
};

/**
 * Asynchronously iterate over an array in parallel.
 * @param {Array} obj
 * @param {Function} iter
 * @param {Function} callback
 */

utils.forEach = function forEach(obj, iter, callback) {
  var pending = obj.length;
  var error;

  callback = utils.asyncify(callback);

  if (!pending)
    return callback();

  function next(err) {
    assert(pending > 0);
    if (err)
      error = err;
    if (!--pending)
      callback(error);
  }

  obj.forEach(function(item, i) {
    iter(item, next, i);
  });
};

/**
 * Asnchronously iterate over a range in serial.
 * @param {Number} from
 * @param {Number} to
 * @param {Function} iter
 * @param {Function} callback
 */

utils.forRangeSerial = function forRangeSerial(from, to, iter, callback) {
  var called = false;

  callback = utils.ensure(callback);

  (function next(err) {
    assert(!called);
    if (err) {
      called = true;
      return callback(err);
    }
    if (from >= to) {
      called = true;
      return callback();
    }
    from++;
    utils.nextTick(function() {
      iter(from - 1, next, from - 1);
    });
  })();
};

/**
 * Asynchronously iterate over an array in serial.
 * @param {Array} obj
 * @param {Function} iter
 * @param {Function} callback
 */

utils.forEachSerial = function forEachSerial(obj, iter, callback) {
  var i = 0;
  var called = false;

  callback = utils.ensure(callback);

  (function next(err) {
    var item;
    assert(!called);
    if (err) {
      called = true;
      return callback(err);
    }
    if (i >= obj.length) {
      called = true;
      return callback();
    }
    item = obj[i];
    i++;
    utils.nextTick(function() {
      iter(item, next, i - 1);
    });
  })();
};

/**
 * Asynchronously apply a truth test to every
 * member of an array in parallel.
 * @param {Array} obj
 * @param {Function} iter
 * @param {Function} callback
 */

utils.every = function every(obj, iter, callback) {
  var pending = obj.length;
  var result = true;
  var error;

  callback = utils.asyncify(callback);

  if (!pending)
    return callback(null, result);

  function next(err, res) {
    assert(pending > 0);
    if (err)
      error = err;
    if (!res)
      result = false;
    if (!--pending) {
      if (error)
        return callback(error);
      callback(null, result);
    }
  }

  obj.forEach(function(item, i) {
    iter(item, next, i);
  });
};

/**
 * Asynchronously apply a truth test to every
 * member of an array in serial.
 * @param {Array} obj
 * @param {Function} iter
 * @param {Function} callback
 */

utils.everySerial = function everySerial(obj, iter, callback) {
  var i = 0;
  var called = false;

  callback = utils.ensure(callback);

  (function next(err, res) {
    var item;
    assert(!called);
    if (err) {
      called = true;
      return callback(err);
    }
    if (!res) {
      called = true;
      return callback(null, false);
    }
    if (i >= obj.length) {
      called = true;
      return callback(null, true);
    }
    item = obj[i];
    i++;
    utils.nextTick(function() {
      iter(item, next, i - 1);
    });
  })(null, true);
};

/**
 * Convert bytes to mb.
 * @param {Number} size
 * @returns {Number} mb
 */

utils.mb = function mb(size) {
  return size / 1024 / 1024 | 0;
};

/**
 * Inheritance.
 * @param {Function} obj - Constructor to inherit.
 * @param {Function} from - Parent constructor.
 */

utils.inherits = function inherits(obj, from) {
  var f;

  obj.super_ = from;

  if (Object.setPrototypeOf) {
    Object.setPrototypeOf(obj.prototype, from.prototype);
    Object.defineProperty(obj.prototype, 'constructor', {
      value: obj,
      enumerable: false
    });
    return;
  }

  if (Object.create) {
    obj.prototype = Object.create(from.prototype, {
      constructor: {
        value: obj,
        enumerable: false
      }
    });
    return;
  }

  f = function() {};
  f.prototype = from.prototype;
  obj.prototype = new f;
  obj.prototype.constructor = obj;
};

/**
 * Wrap a callback to ensure it is only called once.
 * @param {Function} callback
 * @returns {Function} Wrapped callback.
 */

utils.once = function once(callback) {
  var called;

  if (callback && callback._once)
    return callback;

  function onceFn(err, result1, result2) {
    if (called)
      return;
    called = true;
    if (callback)
      callback(err, result1, result2);
  }

  onceFn._once = true;
  if (callback)
    onceFn._asyncified = callback._asyncified;

  return onceFn;
};

/**
 * Build a merkle tree from leaves.
 * @param {Buffer[]} leaves
 * @returns {Buffer[]} Tree (in rare cases this may return null).
 */

utils.buildMerkleTree = function buildMerkleTree(leaves) {
  var tree = leaves.slice();
  var i, j, size, i2, hash;

  j = 0;
  size = leaves.length;

  for (; size > 1; size = ((size + 1) / 2) | 0) {
    for (i = 0; i < size; i += 2) {
      i2 = Math.min(i + 1, size - 1);
      if (i2 === i + 1 && i2 + 1 === size
          && utils.equal(tree[j + i], tree[j + i2])) {
        return;
      }
      hash = Buffer.concat([tree[j + i], tree[j + i2]]);
      hash = utils.dsha256(hash);
      tree.push(hash);
    }
    j += size;
  }

  if (!tree.length)
    return;

  return tree;
};

/**
 * Calculate merkle root from leaves.
 * @param {Buffer[]} leaves
 * @returns {Buffer?} Merkle root.
 */

utils.getMerkleRoot = function getMerkleRoot(leaves) {
  var tree = utils.buildMerkleTree(leaves);
  if (!tree)
    return;

  return tree[tree.length - 1];
};

/**
 * Collect a merkle branch at vector index.
 * @param {Number} index
 * @param {Buffer[]} leaves
 * @returns {Buffer[]} branch
 */

utils.getMerkleBranch = function getMerkleBranch(index, leaves) {
  var tree = utils.buildMerkleTree(leaves);
  var size = leaves.length;
  var branch = [];
  var j = 0;
  var i;

  for (; size > 1; size = (size + 1) / 2 | 0) {
    i = Math.min(index ^ 1, size - 1);
    branch.push(tree[j + i]);
    index >>>= 1;
    j += size;
  }

  return branch;
};

/**
 * Check a merkle branch at vector index.
 * @param {Buffer} hash
 * @param {Buffer[]} branch
 * @param {Number} index
 * @returns {Buffer} Hash.
 */

utils.checkMerkleBranch = function checkMerkleBranch(hash, branch, index) {
  var otherside, i;

  if (index === -1)
    return false;

  if (typeof hash === 'string')
    hash = new Buffer(hash, 'hex');

  for (i = 0; i < branch.length; i++) {
    otherside = branch[i];

    if (index & 1)
      hash = utils.dsha256(Buffer.concat([otherside, hash]));
    else
      hash = utils.dsha256(Buffer.concat([hash, otherside]));

    index >>>= 1;
  }

  return hash;
};

/**
 * Find index of a buffer in an array of buffers.
 * @param {Buffer[]} obj
 * @param {Buffer} data - Target buffer to find.
 * @returns {Number} Index (-1 if not found).
 */

utils.indexOf = function indexOf(obj, data) {
  var i;

  assert(Array.isArray(obj));
  assert(Buffer.isBuffer(data));

  for (i = 0; i < obj.length; i++) {
    if (!Buffer.isBuffer(obj[i]))
      continue;
    if (utils.equal(obj[i], data))
      return i;
  }

  return -1;
};

/**
 * Convert a number to a padded uint32
 * string (10 digits in decimal).
 * @param {Number} num
 * @returns {String} Padded number.
 */

utils.pad32 = function pad32(num) {
  assert(num >= 0);
  num = num + '';
  while (num.length < 10)
    num = '0' + num;
  assert(num.length === 10);
  return num;
};

/**
 * Wrap a callback with an `unlock` callback.
 * @see Locker
 * @param {Function} callback
 * @param {Function} unlock
 * @returns {Function} Wrapped callback.
 */

utils.wrap = function wrap(callback, unlock) {
  return function(err, res1, res2) {
    unlock();
    if (callback)
      callback(err, res1, res2);
  };
};

/**
 * Execute a stack of functions in parallel.
 * @param {Function[]} stack
 * @param {Function} callback
 */

utils.parallel = function parallel(stack, callback) {
  var pending = stack.length;
  var error;
  var i;

  callback = utils.once(callback);

  if (!pending)
    return utils.nextTick(callback);

  function next(err) {
    assert(pending > 0);
    if (err)
      error = err;
    if (!--pending)
      callback(error);
  }

  for (i = 0; i < stack.length; i++) {
    try {
      // if (stack[i].length >= 2) {
      //   stack[i](error, next);
      //   error = null;
      //   continue;
      // }
      if (error)
        continue;
      stack[i](next);
    } catch (e) {
      pending--;
      error = e;
    }
  }
};

/**
 * Execute a stack of functions in serial.
 * @param {Function[]} stack
 * @param {Function} callback
 */

utils.serial = function serial(stack, callback) {
  var i = 0;
  (function next(err) {
    var cb = stack[i++];

    if (!cb)
      return callback(err);

    // if (cb.length >= 2) {
    //   try {
    //     return cb(err, next);
    //   } catch (e) {
    //     return next(e);
    //   }
    // }

    if (err)
      return utils.nextTick(next.bind(null, err));

    try {
      return cb(next);
    } catch (e) {
      return next(e);
    }
  })();
};

/**
 * Convert an array to a map.
 * @param {String[]} obj
 * @returns {Object} Map.
 */

utils.toMap = function toMap(obj) {
  var map = {};
  var i, value;

  for (i = 0; i < obj.length; i++) {
    value = obj[i];
    map[value] = true;
  }

  return map;
};

/**
 * Reverse a map.
 * @param {Object} map
 * @param {Object} Reversed map.
 */

utils.revMap = function revMap(map) {
  var reversed = {};
  var keys = Object.keys(map);
  var i, key;

  for (i = 0; i < keys.length; i++) {
    key = keys[i];
    reversed[map[key]] = key;
  }

  return reversed;
};

/**
 * Perform a binary search on a sorted array.
 * @param {Array} items
 * @param {Object} key
 * @param {Function} compare
 * @param {Boolean?} insert
 * @returns {Number} Index.
 */

utils.binarySearch = function binarySearch(items, key, compare, insert) {
  var start = 0;
  var end = items.length - 1;
  var pos, cmp;

  while (start <= end) {
    pos = (start + end) >>> 1;
    cmp = compare(items[pos], key);

    if (cmp === 0)
      return pos;

    if (cmp < 0)
      start = pos + 1;
    else
      end = pos - 1;
  }

  if (!insert)
    return -1;

  return start;
};

/**
 * Perform a binary insert on a sorted array.
 * @param {Array} items
 * @param {Object} item
 * @param {Function?} compare
 * @returns {Number} Length.
 */

utils.binaryInsert = function binaryInsert(items, item, compare) {
  var i = utils.binarySearch(items, item, compare, true);
  items.splice(i, 0, item);
  return items.length;
};

/**
 * Perform a binary removal on a sorted array.
 * @param {Array} items
 * @param {Object} item
 * @param {Function?} compare
 * @returns {Number} Length.
 */

utils.binaryRemove = function binaryRemove(items, item, compare) {
  var i = utils.binarySearch(items, item, compare, false);
  if (i === -1)
    return false;
  items.splice(i, 1);
  return true;
};

/**
 * Reference to the global object.
 * @const {Object}
 */

utils.global = (function() {
  /* global self */

  if (this)
    return this;

  if (typeof window !== 'undefined')
    return window;

  if (typeof self !== 'undefined')
    return self;

  if (typeof global !== 'undefined')
    return global;
})();