util.js

/* eslint guard-for-in:0 */

var cryptoLib = require('crypto');
var Buffer = require('buffer').Buffer;
var AWS;

/**
 * A set of utility methods for use with the AWS SDK.
 *
 * @!attribute abort
 *   Return this value from an iterator function {each} or {arrayEach}
 *   to break out of the iteration.
 *   @example Breaking out of an iterator function
 *     AWS.util.each({a: 1, b: 2, c: 3}, function(key, value) {
 *       if (key == 'b') return AWS.util.abort;
 *     });
 *   @see each
 *   @see arrayEach
 * @api private
 */
var util = {
  engine: function engine() {
    if (util.isBrowser() && typeof navigator !== 'undefined') {
      return navigator.userAgent;
    } else {
      return process.platform + '/' + process.version;
    }
  },

  userAgent: function userAgent() {
    var name = util.isBrowser() ? 'js' : 'nodejs';
    var agent = 'aws-sdk-' + name + '/' + require('./core').VERSION;
    if (name === 'nodejs') agent += ' ' + util.engine();
    return agent;
  },

  isBrowser: function isBrowser() { return process && process.browser; },
  isNode: function isNode() { return !util.isBrowser(); },
  nodeRequire: function nodeRequire(module) {
    if (util.isNode()) return require(module);
  },
  multiRequire: function multiRequire(module1, module2) {
    return require(util.isNode() ? module1 : module2);
  },

  uriEscape: function uriEscape(string) {
    var output = encodeURIComponent(string);
    output = output.replace(/[^A-Za-z0-9_.~\-%]+/g, escape);

    // AWS percent-encodes some extra non-standard characters in a URI
    output = output.replace(/[*]/g, function(ch) {
      return '%' + ch.charCodeAt(0).toString(16).toUpperCase();
    });

    return output;
  },

  uriEscapePath: function uriEscapePath(string) {
    var parts = [];
    util.arrayEach(string.split('/'), function (part) {
      parts.push(util.uriEscape(part));
    });
    return parts.join('/');
  },

  urlParse: function urlParse(url) {
    return require('url').parse(url);
  },

  urlFormat: function urlFormat(url) {
    return require('url').format(url);
  },

  queryStringParse: function queryStringParse(qs) {
    return require('querystring').parse(qs);
  },

  queryParamsToString: function queryParamsToString(params) {
    var items = [];
    var escape = util.uriEscape;
    var sortedKeys = Object.keys(params).sort();

    util.arrayEach(sortedKeys, function(name) {
      var value = params[name];
      var ename = escape(name);
      var result = ename + '=';
      if (Array.isArray(value)) {
        var vals = [];
        util.arrayEach(value, function(item) { vals.push(escape(item)); });
        result = ename + '=' + vals.sort().join('&' + ename + '=');
      } else if (value !== undefined && value !== null) {
        result = ename + '=' + escape(value);
      }
      items.push(result);
    });

    return items.join('&');
  },

  readFileSync: function readFileSync(path) {
    if (typeof window !== 'undefined') return null;
    return util.nodeRequire('fs').readFileSync(path, 'utf-8');
  },

  base64: {

    encode: function encode64(string) {
      return new Buffer(string).toString('base64');
    },

    decode: function decode64(string) {
      return new Buffer(string, 'base64');
    }

  },

  Buffer: Buffer,

  buffer: {
    toStream: function toStream(buffer) {
      if (!util.Buffer.isBuffer(buffer)) buffer = new util.Buffer(buffer);

      var readable = new (util.nodeRequire('stream').Readable)();
      var pos = 0;
      readable._read = function(size) {
        if (pos >= buffer.length) return readable.push(null);

        var end = pos + size;
        if (end > buffer.length) end = buffer.length;
        readable.push(buffer.slice(pos, end));
        pos = end;
      };

      return readable;
    },

    /**
     * Concatenates a list of Buffer objects.
     */
    concat: function(buffers) {
      var length = 0,
          offset = 0,
          buffer = null, i;

      for (i = 0; i < buffers.length; i++) {
        length += buffers[i].length;
      }

      buffer = new Buffer(length);

      for (i = 0; i < buffers.length; i++) {
        buffers[i].copy(buffer, offset);
        offset += buffers[i].length;
      }

      return buffer;
    }
  },

  string: {
    byteLength: function byteLength(string) {
      if (string === null || string === undefined) return 0;
      if (typeof string === 'string') string = new Buffer(string);

      if (typeof string.byteLength === 'number') {
        return string.byteLength;
      } else if (typeof string.length === 'number') {
        return string.length;
      } else if (typeof string.size === 'number') {
        return string.size;
      } else if (typeof string.path === 'string') {
        return util.nodeRequire('fs').lstatSync(string.path).size;
      } else {
        throw util.error(new Error('Cannot determine length of ' + string),
          { object: string });
      }
    },

    upperFirst: function upperFirst(string) {
      return string[0].toUpperCase() + string.substr(1);
    },

    lowerFirst: function lowerFirst(string) {
      return string[0].toLowerCase() + string.substr(1);
    }
  },

  ini: {
    parse: function string(ini) {
      var currentSection, map = {};
      util.arrayEach(ini.split(/\r?\n/), function(line) {
        line = line.split(/(^|\s);/)[0]; // remove comments
        var section = line.match(/^\s*\[([^\[\]]+)\]\s*$/);
        if (section) {
          currentSection = section[1];
        } else if (currentSection) {
          var item = line.match(/^\s*(.+?)\s*=\s*(.+?)\s*$/);
          if (item) {
            map[currentSection] = map[currentSection] || {};
            map[currentSection][item[1]] = item[2];
          }
        }
      });

      return map;
    }
  },

  fn: {
    noop: function() {},

    /**
     * Turn a synchronous function into as "async" function by making it call
     * a callback. The underlying function is called with all but the last argument,
     * which is treated as the callback. The callback is passed passed a first argument
     * of null on success to mimick standard node callbacks.
     */
    makeAsync: function makeAsync(fn, expectedArgs) {
      if (expectedArgs && expectedArgs <= fn.length) {
        return fn;
      }

      return function() {
        var args = Array.prototype.slice.call(arguments, 0);
        var callback = args.pop();
        var result = fn.apply(null, args);
        callback(result);
      };
    }
  },

  jamespath: {
    query: function query(expression, data) {
      if (!data) return [];

      var results = [];
      var expressions = expression.split(/\s+\|\|\s+/);
      util.arrayEach.call(this, expressions, function (expr) {
        var objects = [data];
        var tokens = expr.split('.');
        util.arrayEach.call(this, tokens, function (token) {
          var match = token.match('^(.+?)(?:\\[(-?\\d+|\\*|)\\])?$');
          var newObjects = [];
          util.arrayEach.call(this, objects, function (obj) {
            if (match[1] === '*') {
              util.arrayEach.call(this, obj, function (value) {
                newObjects.push(value);
              });
            } else if (obj.hasOwnProperty(match[1])) {
              newObjects.push(obj[match[1]]);
            }
          });
          objects = newObjects;

          // handle indexing (token[0], token[-1])
          if (match[2] !== undefined) {
            newObjects = [];
            util.arrayEach.call(this, objects, function (obj) {
              if (Array.isArray(obj)) {
                if (match[2] === '*' || match[2] === '') {
                  newObjects = newObjects.concat(obj);
                } else {
                  var idx = parseInt(match[2], 10);
                  if (idx < 0) idx = obj.length + idx; // negative indexing
                  newObjects.push(obj[idx]);
                }
              }
            });
            objects = newObjects;
          }

          if (objects.length === 0) return util.abort;
        });

        if (objects.length > 0) {
          results = objects;
          return util.abort;
        }
      });

      return results;
    },

    find: function find(expression, data) {
      return util.jamespath.query(expression, data)[0];
    }
  },

  /**
   * Date and time utility functions.
   */
  date: {

    /**
     * @return [Date] the current JavaScript date object. Since all
     *   AWS services rely on this date object, you can override
     *   this function to provide a special time value to AWS service
     *   requests.
     */
    getDate: function getDate() {
      if (!AWS) AWS = require('./core');
      if (AWS.config.systemClockOffset) { // use offset when non-zero
        return new Date(new Date().getTime() + AWS.config.systemClockOffset);
      } else {
        return new Date();
      }
    },

    /**
     * @return [String] the date in ISO-8601 format
     */
    iso8601: function iso8601(date) {
      if (date === undefined) { date = util.date.getDate(); }
      return date.toISOString().replace(/\.\d{3}Z$/, 'Z');
    },

    /**
     * @return [String] the date in RFC 822 format
     */
    rfc822: function rfc822(date) {
      if (date === undefined) { date = util.date.getDate(); }
      return date.toUTCString();
    },

    /**
     * @return [Integer] the UNIX timestamp value for the current time
     */
    unixTimestamp: function unixTimestamp(date) {
      if (date === undefined) { date = util.date.getDate(); }
      return date.getTime() / 1000;
    },

    /**
     * @param [String,number,Date] date
     * @return [Date]
     */
    from: function format(date) {
      if (typeof date === 'number') {
        return new Date(date * 1000); // unix timestamp
      } else {
        return new Date(date);
      }
    },

    /**
     * Given a Date or date-like value, this function formats the
     * date into a string of the requested value.
     * @param [String,number,Date] date
     * @param [String] formatter Valid formats are:
     #   * 'iso8601'
     #   * 'rfc822'
     #   * 'unixTimestamp'
     * @return [String]
     */
    format: function format(date, formatter) {
      if (!formatter) formatter = 'iso8601';
      return util.date[formatter](util.date.from(date));
    },

    parseTimestamp: function parseTimestamp(value) {
      if (typeof value === 'number') { // unix timestamp (number)
        return new Date(value * 1000);
      } else if (value.match(/^\d+$/)) { // unix timestamp
        return new Date(value * 1000);
      } else if (value.match(/^\d{4}/)) { // iso8601
        return new Date(value);
      } else if (value.match(/^\w{3},/)) { // rfc822
        return new Date(value);
      } else {
        throw util.error(
          new Error('unhandled timestamp format: ' + value),
          {code: 'TimestampParserError'});
      }
    }

  },

  crypto: {
    crc32Table: [
     0x00000000, 0x77073096, 0xEE0E612C, 0x990951BA, 0x076DC419,
     0x706AF48F, 0xE963A535, 0x9E6495A3, 0x0EDB8832, 0x79DCB8A4,
     0xE0D5E91E, 0x97D2D988, 0x09B64C2B, 0x7EB17CBD, 0xE7B82D07,
     0x90BF1D91, 0x1DB71064, 0x6AB020F2, 0xF3B97148, 0x84BE41DE,
     0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7, 0x136C9856,
     0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
     0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4,
     0xA2677172, 0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B,
     0x35B5A8FA, 0x42B2986C, 0xDBBBC9D6, 0xACBCF940, 0x32D86CE3,
     0x45DF5C75, 0xDCD60DCF, 0xABD13D59, 0x26D930AC, 0x51DE003A,
     0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423, 0xCFBA9599,
     0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
     0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190,
     0x01DB7106, 0x98D220BC, 0xEFD5102A, 0x71B18589, 0x06B6B51F,
     0x9FBFE4A5, 0xE8B8D433, 0x7807C9A2, 0x0F00F934, 0x9609A88E,
     0xE10E9818, 0x7F6A0DBB, 0x086D3D2D, 0x91646C97, 0xE6635C01,
     0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E, 0x6C0695ED,
     0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
     0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3,
     0xFBD44C65, 0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2,
     0x4ADFA541, 0x3DD895D7, 0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A,
     0x346ED9FC, 0xAD678846, 0xDA60B8D0, 0x44042D73, 0x33031DE5,
     0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA, 0xBE0B1010,
     0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
     0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17,
     0x2EB40D81, 0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6,
     0x03B6E20C, 0x74B1D29A, 0xEAD54739, 0x9DD277AF, 0x04DB2615,
     0x73DC1683, 0xE3630B12, 0x94643B84, 0x0D6D6A3E, 0x7A6A5AA8,
     0xE40ECF0B, 0x9309FF9D, 0x0A00AE27, 0x7D079EB1, 0xF00F9344,
     0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
     0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A,
     0x67DD4ACC, 0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5,
     0xD6D6A3E8, 0xA1D1937E, 0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1,
     0xA6BC5767, 0x3FB506DD, 0x48B2364B, 0xD80D2BDA, 0xAF0A1B4C,
     0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55, 0x316E8EEF,
     0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
     0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE,
     0xB2BD0B28, 0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31,
     0x2CD99E8B, 0x5BDEAE1D, 0x9B64C2B0, 0xEC63F226, 0x756AA39C,
     0x026D930A, 0x9C0906A9, 0xEB0E363F, 0x72076785, 0x05005713,
     0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0x0CB61B38, 0x92D28E9B,
     0xE5D5BE0D, 0x7CDCEFB7, 0x0BDBDF21, 0x86D3D2D4, 0xF1D4E242,
     0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1,
     0x18B74777, 0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C,
     0x8F659EFF, 0xF862AE69, 0x616BFFD3, 0x166CCF45, 0xA00AE278,
     0xD70DD2EE, 0x4E048354, 0x3903B3C2, 0xA7672661, 0xD06016F7,
     0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC, 0x40DF0B66,
     0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
     0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605,
     0xCDD70693, 0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8,
     0x5D681B02, 0x2A6F2B94, 0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B,
     0x2D02EF8D],

    crc32: function crc32(data) {
      var tbl = util.crypto.crc32Table;
      var crc = 0 ^ -1;

      if (typeof data === 'string') {
        data = new Buffer(data);
      }

      for (var i = 0; i < data.length; i++) {
        var code = data.readUInt8(i);
        crc = (crc >>> 8) ^ tbl[(crc ^ code) & 0xFF];
      }
      return (crc ^ -1) >>> 0;
    },

    hmac: function hmac(key, string, digest, fn) {
      if (!digest) digest = 'binary';
      if (digest === 'buffer') { digest = undefined; }
      if (!fn) fn = 'sha256';
      if (typeof string === 'string') string = new Buffer(string);
      return cryptoLib.createHmac(fn, key).update(string).digest(digest);
    },

    md5: function md5(data, digest, callback) {
      return util.crypto.hash('md5', data, digest, callback);
    },

    sha256: function sha256(data, digest, callback) {
      return util.crypto.hash('sha256', data, digest, callback);
    },

    hash: function(algorithm, data, digest, callback) {
      var hash = util.crypto.createHash(algorithm);
      if (!digest) { digest = 'binary'; }
      if (digest === 'buffer') { digest = undefined; }
      if (typeof data === 'string') data = new Buffer(data);
      var sliceFn = util.arraySliceFn(data);
      var isBuffer = Buffer.isBuffer(data);

      if (callback && typeof data === 'object' &&
          typeof data.on === 'function' && !isBuffer) {
        data.on('data', function(chunk) { hash.update(chunk); });
        data.on('error', function(err) { callback(err); });
        data.on('end', function() { callback(null, hash.digest(digest)); });
      } else if (callback && sliceFn && !isBuffer &&
                 typeof FileReader !== 'undefined') {
        // this might be a File/Blob
        var index = 0, size = 1024 * 512;
        var reader = new FileReader();
        reader.onerror = function() {
          callback(new Error('Failed to read data.'));
        };
        reader.onload = function() {
          var buf = new Buffer(new Uint8Array(reader.result));
          hash.update(buf);
          index += buf.length;
          reader._continueReading();
        };
        reader._continueReading = function() {
          if (index >= data.size) {
            callback(null, hash.digest(digest));
            return;
          }

          var back = index + size;
          if (back > data.size) back = data.size;
          reader.readAsArrayBuffer(sliceFn.call(data, index, back));
        };

        reader._continueReading();
      } else {
        if (util.isBrowser() && typeof data === 'object' && !isBuffer) {
          data = new Buffer(new Uint8Array(data));
        }
        var out = hash.update(data).digest(digest);
        if (callback) callback(null, out);
        return out;
      }
    },

    toHex: function toHex(data) {
      var out = [];
      for (var i = 0; i < data.length; i++) {
        out.push(('0' + data.charCodeAt(i).toString(16)).substr(-2, 2));
      }
      return out.join('');
    },

    createHash: function createHash(algorithm) {
      return cryptoLib.createHash(algorithm);
    }

  },

  /** @!ignore */

  /* Abort constant */
  abort: {},

  each: function each(object, iterFunction) {
    for (var key in object) {
      if (object.hasOwnProperty(key)) {
        var ret = iterFunction.call(this, key, object[key]);
        if (ret === util.abort) break;
      }
    }
  },

  arrayEach: function arrayEach(array, iterFunction) {
    for (var idx in array) {
      if (array.hasOwnProperty(idx)) {
        var ret = iterFunction.call(this, array[idx], parseInt(idx, 10));
        if (ret === util.abort) break;
      }
    }
  },

  update: function update(obj1, obj2) {
    util.each(obj2, function iterator(key, item) {
      obj1[key] = item;
    });
    return obj1;
  },

  merge: function merge(obj1, obj2) {
    return util.update(util.copy(obj1), obj2);
  },

  copy: function copy(object) {
    if (object === null || object === undefined) return object;
    var dupe = {};
    // jshint forin:false
    for (var key in object) {
      dupe[key] = object[key];
    }
    return dupe;
  },

  isEmpty: function isEmpty(obj) {
    for (var prop in obj) {
      if (obj.hasOwnProperty(prop)) {
        return false;
      }
    }
    return true;
  },

  arraySliceFn: function arraySliceFn(obj) {
    var fn = obj.slice || obj.webkitSlice || obj.mozSlice;
    return typeof fn === 'function' ? fn : null;
  },

  isType: function isType(obj, type) {
    // handle cross-"frame" objects
    if (typeof type === 'function') type = util.typeName(type);
    return Object.prototype.toString.call(obj) === '[object ' + type + ']';
  },

  typeName: function typeName(type) {
    if (type.hasOwnProperty('name')) return type.name;
    var str = type.toString();
    var match = str.match(/^\s*function (.+)\(/);
    return match ? match[1] : str;
  },

  error: function error(err, options) {
    var originalError = null;
    if (typeof err.message === 'string' && err.message !== '') {
      if (typeof options === 'string' || (options && options.message)) {
        originalError = util.copy(err);
        originalError.message = err.message;
      }
    }
    err.message = err.message || null;

    if (typeof options === 'string') {
      err.message = options;
    } else {
      util.update(err, options);
    }

    if (typeof Object.defineProperty === 'function') {
      Object.defineProperty(err, 'name', {writable: true, enumerable: false});
      Object.defineProperty(err, 'message', {enumerable: true});
    }

    err.name = err.name || err.code || 'Error';
    err.time = new Date();

    if (originalError) err.originalError = originalError;

    return err;
  },

  /**
   * @api private
   */
  inherit: function inherit(klass, features) {
    var newObject = null;
    if (features === undefined) {
      features = klass;
      klass = Object;
      newObject = {};
    } else {
      var ctor = function ConstructorWrapper() {};
      ctor.prototype = klass.prototype;
      newObject = new ctor();
    }

    // constructor not supplied, create pass-through ctor
    if (features.constructor === Object) {
      features.constructor = function() {
        if (klass !== Object) {
          return klass.apply(this, arguments);
        }
      };
    }

    features.constructor.prototype = newObject;
    util.update(features.constructor.prototype, features);
    features.constructor.__super__ = klass;
    return features.constructor;
  },

  /**
   * @api private
   */
  mixin: function mixin() {
    var klass = arguments[0];
    for (var i = 1; i < arguments.length; i++) {
      // jshint forin:false
      for (var prop in arguments[i].prototype) {
        var fn = arguments[i].prototype[prop];
        if (prop !== 'constructor') {
          klass.prototype[prop] = fn;
        }
      }
    }
    return klass;
  },

  /**
   * @api private
   */
  hideProperties: function hideProperties(obj, props) {
    if (typeof Object.defineProperty !== 'function') return;

    util.arrayEach(props, function (key) {
      Object.defineProperty(obj, key, {
        enumerable: false, writable: true, configurable: true });
    });
  },

  /**
   * @api private
   */
  property: function property(obj, name, value, enumerable, isValue) {
    var opts = {
      configurable: true,
      enumerable: enumerable !== undefined ? enumerable : true
    };
    if (typeof value === 'function' && !isValue) {
      opts.get = value;
    }
    else {
      opts.value = value; opts.writable = true;
    }

    Object.defineProperty(obj, name, opts);
  },

  /**
   * @api private
   */
  memoizedProperty: function memoizedProperty(obj, name, get, enumerable) {
    var cachedValue = null;

    // build enumerable attribute for each value with lazy accessor.
    util.property(obj, name, function() {
      if (cachedValue === null) {
        cachedValue = get();
      }
      return cachedValue;
    }, enumerable);
  },

  /**
   * TODO Remove in major version revision
   * This backfill populates response data without the
   * top-level payload name.
   *
   * @api private
   */
  hoistPayloadMember: function hoistPayloadMember(resp) {
    var req = resp.request;
    var operation = req.operation;
    var output = req.service.api.operations[operation].output;
    if (output.payload) {
      var payloadMember = output.members[output.payload];
      var responsePayload = resp.data[output.payload];
      if (payloadMember.type === 'structure') {
        AWS.util.each(responsePayload, function(key, value) {
          AWS.util.property(resp.data, key, value, false);
        });
      }
    }
  },

  /**
   * Compute SHA-256 checksums of streams
   *
   * @api private
   */
  computeSha256: function computeSha256(body, done) {
    if (AWS.util.isNode()) {
      var Stream = AWS.util.nodeRequire('stream').Stream;
      var fs = AWS.util.nodeRequire('fs');
      if (body instanceof Stream) {
        if (typeof body.path === 'string') { // assume file object
          body = fs.createReadStream(body.path);
        } else { // TODO support other stream types
          return done(new Error('Non-file stream objects are ' +
                                'not supported with SigV4'));
        }
      }
    }

    AWS.util.crypto.sha256(body, 'hex', function(err, sha) {
      if (err) done(err);
      else done(null, sha);
    });
  }

};

module.exports = util;