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node_modules/vary/index.js 2.52 KB
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f7563de62   Palak Handa   first commit 
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  /*!
   * vary
   * Copyright(c) 2014-2017 Douglas Christopher Wilson
   * MIT Licensed
   */
  
  'use strict'
  
  /**
   * Module exports.
   */
  
  module.exports = vary
  module.exports.append = append
  
  /**
   * Regular expression to split on commas, trimming spaces
   * @private
   */
  
  var ARRAY_SPLIT_REGEXP = / *, */
  
  /**
   * RegExp to match field-name in RFC 7230 sec 3.2
   *
   * field-name    = token
   * token         = 1*tchar
   * tchar         = "!" / "#" / "$" / "%" / "&" / "'" / "*"
   *               / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
   *               / DIGIT / ALPHA
   *               ; any VCHAR, except delimiters
   */
  
  var FIELD_NAME_REGEXP = /^[!#$%&'*+\-.^_`|~0-9A-Za-z]+$/
  
  /**
   * Append a field to a vary header.
   *
   * @param {String} header
   * @param {String|Array} field
   * @return {String}
   * @public
   */
  
  function append (header, field) {
    if (typeof header !== 'string') {
      throw new TypeError('header argument is required')
    }
  
    if (!field) {
      throw new TypeError('field argument is required')
    }
  
    // get fields array
    var fields = !Array.isArray(field)
      ? parse(String(field))
      : field
  
    // assert on invalid field names
    for (var j = 0; j < fields.length; j++) {
      if (!FIELD_NAME_REGEXP.test(fields[j])) {
        throw new TypeError('field argument contains an invalid header name')
      }
    }
  
    // existing, unspecified vary
    if (header === '*') {
      return header
    }
  
    // enumerate current values
    var val = header
    var vals = parse(header.toLowerCase())
  
    // unspecified vary
    if (fields.indexOf('*') !== -1 || vals.indexOf('*') !== -1) {
      return '*'
    }
  
    for (var i = 0; i < fields.length; i++) {
      var fld = fields[i].toLowerCase()
  
      // append value (case-preserving)
      if (vals.indexOf(fld) === -1) {
        vals.push(fld)
        val = val
          ? val + ', ' + fields[i]
          : fields[i]
      }
    }
  
    return val
  }
  
  /**
   * Parse a vary header into an array.
   *
   * @param {String} header
   * @return {Array}
   * @private
   */
  
  function parse (header) {
    return header.trim().split(ARRAY_SPLIT_REGEXP)
  }
  
  /**
   * Mark that a request is varied on a header field.
   *
   * @param {Object} res
   * @param {String|Array} field
   * @public
   */
  
  function vary (res, field) {
    if (!res || !res.getHeader || !res.setHeader) {
      // quack quack
      throw new TypeError('res argument is required')
    }
  
    // get existing header
    var val = res.getHeader('Vary') || ''
    var header = Array.isArray(val)
      ? val.join(', ')
      : String(val)
  
    // set new header
    if ((val = append(header, field))) {
      res.setHeader('Vary', val)
    }
  }