node/lib/internal/util.js

'use strict';

const binding = process.binding('util');

const kArrowMessagePrivateSymbolIndex = binding['arrow_message_private_symbol'];
const kDecoratedPrivateSymbolIndex = binding['decorated_private_symbol'];

// The `buffer` module uses this. Defining it here instead of in the public
// `util` module makes it accessible without having to `require('util')` there.
exports.customInspectSymbol = Symbol('util.inspect.custom');

// Mark that a method should not be used.
// Returns a modified function which warns once by default.
// If --no-deprecation is set, then it is a no-op.
exports.deprecate = function deprecate(fn, msg, code) {
  // Allow for deprecating things in the process of starting up.
  if (global.process === undefined) {
    return function() {
      return exports.deprecate(fn, msg, code).apply(this, arguments);
    };
  }

  if (process.noDeprecation === true) {
    return fn;
  }

  if (code !== undefined && typeof code !== 'string')
    throw new TypeError('`code` argument must be a string');

  var warned = false;
  function deprecated() {
    if (!warned) {
      warned = true;
      if (code !== undefined) {
        process.emitWarning(msg, 'DeprecationWarning', code, deprecated);
      } else {
        process.emitWarning(msg, 'DeprecationWarning', deprecated);
      }
    }
    if (new.target) {
      return Reflect.construct(fn, arguments, new.target);
    }
    return fn.apply(this, arguments);
  }

  // The wrapper will keep the same prototype as fn to maintain prototype chain
  Object.setPrototypeOf(deprecated, fn);
  if (fn.prototype) {
    // Setting this (rather than using Object.setPrototype, as above) ensures
    // that calling the unwrapped constructor gives an instanceof the wrapped
    // constructor.
    deprecated.prototype = fn.prototype;
  }

  return deprecated;
};

exports.decorateErrorStack = function decorateErrorStack(err) {
  if (!(exports.isError(err) && err.stack) ||
      binding.getHiddenValue(err, kDecoratedPrivateSymbolIndex) === true)
    return;

  const arrow = binding.getHiddenValue(err, kArrowMessagePrivateSymbolIndex);

  if (arrow) {
    err.stack = arrow + err.stack;
    binding.setHiddenValue(err, kDecoratedPrivateSymbolIndex, true);
  }
};

exports.isError = function isError(e) {
  return exports.objectToString(e) === '[object Error]' || e instanceof Error;
};

exports.objectToString = function objectToString(o) {
  return Object.prototype.toString.call(o);
};

const noCrypto = !process.versions.openssl;
exports.assertCrypto = function() {
  if (noCrypto)
    throw new Error('Node.js is not compiled with openssl crypto support');
};

exports.kIsEncodingSymbol = Symbol('node.isEncoding');

// The loop should only run at most twice, retrying with lowercased enc
// if there is no match in the first pass.
// We use a loop instead of branching to retry with a helper
// function in order to avoid the performance hit.
// Return undefined if there is no match.
exports.normalizeEncoding = function normalizeEncoding(enc) {
  if (!enc) return 'utf8';
  var retried;
  while (true) {
    switch (enc) {
      case 'utf8':
      case 'utf-8':
        return 'utf8';
      case 'ucs2':
      case 'ucs-2':
      case 'utf16le':
      case 'utf-16le':
        return 'utf16le';
      case 'latin1':
      case 'binary':
        return 'latin1';
      case 'base64':
      case 'ascii':
      case 'hex':
        return enc;
      default:
        if (retried) return; // undefined
        enc = ('' + enc).toLowerCase();
        retried = true;
    }
  }
};

// Filters duplicate strings. Used to support functions in crypto and tls
// modules. Implemented specifically to maintain existing behaviors in each.
exports.filterDuplicateStrings = function filterDuplicateStrings(items, low) {
  const map = new Map();
  for (var i = 0; i < items.length; i++) {
    const item = items[i];
    const key = item.toLowerCase();
    if (low) {
      map.set(key, key);
    } else {
      map.set(key, item);
    }
  }
  return Array.from(map.values()).sort();
};

exports.cachedResult = function cachedResult(fn) {
  var result;
  return () => {
    if (result === undefined)
      result = fn();
    return result.slice();
  };
};

/*
 * Implementation of ToInteger as per ECMAScript Specification
 * Refer: http://www.ecma-international.org/ecma-262/6.0/#sec-tointeger
 */
const toInteger = exports.toInteger = function toInteger(argument) {
  const number = +argument;
  return Number.isNaN(number) ? 0 : Math.trunc(number);
};

/*
 * Implementation of ToLength as per ECMAScript Specification
 * Refer: http://www.ecma-international.org/ecma-262/6.0/#sec-tolength
 */
exports.toLength = function toLength(argument) {
  const len = toInteger(argument);
  return len <= 0 ? 0 : Math.min(len, Number.MAX_SAFE_INTEGER);
};

// Useful for Wrapping an ES6 Class with a constructor Function that
// does not require the new keyword. For instance:
//   class A { constructor(x) {this.x = x;}}
//   const B = createClassWrapper(A);
//   B() instanceof A // true
//   B() instanceof B // true
exports.createClassWrapper = function createClassWrapper(type) {
  const fn = function(...args) {
    return Reflect.construct(type, args, new.target || type);
  };
  // Mask the wrapper function name and length values
  Object.defineProperties(fn, {
    name: {value: type.name},
    length: {value: type.length}
  });
  Object.setPrototypeOf(fn, type);
  fn.prototype = type.prototype;
  return fn;
};