text: ﻿/**
  * Copyright 2011 Microsoft Corporation
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *   http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
  
  // Module dependencies.
  var crypto = require('crypto');
  
  var azureutil = require('../../util/util');
  var Base64 = require('../../util/base64');
  var HeaderConstants = require('../../util/constants').HeaderConstants;
  
  // Expose 'HmacSHA256Sign'.
  exports = module.exports = HmacSha256Sign;
  
  /**
  * Creates a new HmacSHA256Sign object.
  *
  * @constructor
  */
  function HmacSha256Sign(accessKey) {
    this._accessKey = accessKey;
    this._decodedAccessKey = Base64.decode64(this._accessKey);
  }
  
  /**
  * Computes a signature for the specified string using the HMAC-SHA256 algorithm.
  * 
  * @param {string} stringToSign The UTF-8-encoded string to sign.
  * @return A String that contains the HMAC-SHA256-encoded signature.
  */
  HmacSha256Sign.prototype.sign = function (stringToSign) {
    // Encoding the Signature
    // Signature=Base64(HMAC-SHA256(UTF8(StringToSign)))
  
    return crypto.createHmac('sha256', this._decodedAccessKey).update(stringToSign).digest('base64');
  };