dynatrace-cordova-outsystems-plugin/node_modules/asn1/lib/ber/reader.js

This plugin gives you the ability to use the Dynatrace instrumentation in your hybrid application (Cordova, Ionic, ..). It uses the Mobile Agent, the JavaScript Agent and the Javascript Bridge. The Mobile Agent will give you all device specific values con

// Copyright 2011 Mark Cavage <mcavage@gmail.com> All rights reserved.

var assert = require('assert');
var Buffer = require('safer-buffer').Buffer;

var ASN1 = require('./types');
var errors = require('./errors');


// --- Globals

var newInvalidAsn1Error = errors.newInvalidAsn1Error;



// --- API

function Reader(data) {
  if (!data || !Buffer.isBuffer(data))
    throw new TypeError('data must be a node Buffer');

  this._buf = data;
  this._size = data.length;

  // These hold the "current" state
  this._len = 0;
  this._offset = 0;
}

Object.defineProperty(Reader.prototype, 'length', {
  enumerable: true,
  get: function () { return (this._len); }
});

Object.defineProperty(Reader.prototype, 'offset', {
  enumerable: true,
  get: function () { return (this._offset); }
});

Object.defineProperty(Reader.prototype, 'remain', {
  get: function () { return (this._size - this._offset); }
});

Object.defineProperty(Reader.prototype, 'buffer', {
  get: function () { return (this._buf.slice(this._offset)); }
});


/**
 * Reads a single byte and advances offset; you can pass in `true` to make this
 * a "peek" operation (i.e., get the byte, but don't advance the offset).
 *
 * @param {Boolean} peek true means don't move offset.
 * @return {Number} the next byte, null if not enough data.
 */
Reader.prototype.readByte = function (peek) {
  if (this._size - this._offset < 1)
    return null;

  var b = this._buf[this._offset] & 0xff;

  if (!peek)
    this._offset += 1;

  return b;
};


Reader.prototype.peek = function () {
  return this.readByte(true);
};


/**
 * Reads a (potentially) variable length off the BER buffer.  This call is
 * not really meant to be called directly, as callers have to manipulate
 * the internal buffer afterwards.
 *
 * As a result of this call, you can call `Reader.length`, until the
 * next thing called that does a readLength.
 *
 * @return {Number} the amount of offset to advance the buffer.
 * @throws {InvalidAsn1Error} on bad ASN.1
 */
Reader.prototype.readLength = function (offset) {
  if (offset === undefined)
    offset = this._offset;

  if (offset >= this._size)
    return null;

  var lenB = this._buf[offset++] & 0xff;
  if (lenB === null)
    return null;

  if ((lenB & 0x80) === 0x80) {
    lenB &= 0x7f;

    if (lenB === 0)
      throw newInvalidAsn1Error('Indefinite length not supported');

    if (lenB > 4)
      throw newInvalidAsn1Error('encoding too long');

    if (this._size - offset < lenB)
      return null;

    this._len = 0;
    for (var i = 0; i < lenB; i++)
      this._len = (this._len << 8) + (this._buf[offset++] & 0xff);

  } else {
    // Wasn't a variable length
    this._len = lenB;
  }

  return offset;
};


/**
 * Parses the next sequence in this BER buffer.
 *
 * To get the length of the sequence, call `Reader.length`.
 *
 * @return {Number} the sequence's tag.
 */
Reader.prototype.readSequence = function (tag) {
  var seq = this.peek();
  if (seq === null)
    return null;
  if (tag !== undefined && tag !== seq)
    throw newInvalidAsn1Error('Expected 0x' + tag.toString(16) +
                              ': got 0x' + seq.toString(16));

  var o = this.readLength(this._offset + 1); // stored in `length`
  if (o === null)
    return null;

  this._offset = o;
  return seq;
};


Reader.prototype.readInt = function () {
  return this._readTag(ASN1.Integer);
};


Reader.prototype.readBoolean = function () {
  return (this._readTag(ASN1.Boolean) === 0 ? false : true);
};


Reader.prototype.readEnumeration = function () {
  return this._readTag(ASN1.Enumeration);
};


Reader.prototype.readString = function (tag, retbuf) {
  if (!tag)
    tag = ASN1.OctetString;

  var b = this.peek();
  if (b === null)
    return null;

  if (b !== tag)
    throw newInvalidAsn1Error('Expected 0x' + tag.toString(16) +
                              ': got 0x' + b.toString(16));

  var o = this.readLength(this._offset + 1); // stored in `length`

  if (o === null)
    return null;

  if (this.length > this._size - o)
    return null;

  this._offset = o;

  if (this.length === 0)
    return retbuf ? Buffer.alloc(0) : '';

  var str = this._buf.slice(this._offset, this._offset + this.length);
  this._offset += this.length;

  return retbuf ? str : str.toString('utf8');
};

Reader.prototype.readOID = function (tag) {
  if (!tag)
    tag = ASN1.OID;

  var b = this.readString(tag, true);
  if (b === null)
    return null;

  var values = [];
  var value = 0;

  for (var i = 0; i < b.length; i++) {
    var byte = b[i] & 0xff;

    value <<= 7;
    value += byte & 0x7f;
    if ((byte & 0x80) === 0) {
      values.push(value);
      value = 0;
    }
  }

  value = values.shift();
  values.unshift(value % 40);
  values.unshift((value / 40) >> 0);

  return values.join('.');
};


Reader.prototype._readTag = function (tag) {
  assert.ok(tag !== undefined);

  var b = this.peek();

  if (b === null)
    return null;

  if (b !== tag)
    throw newInvalidAsn1Error('Expected 0x' + tag.toString(16) +
                              ': got 0x' + b.toString(16));

  var o = this.readLength(this._offset + 1); // stored in `length`
  if (o === null)
    return null;

  if (this.length > 4)
    throw newInvalidAsn1Error('Integer too long: ' + this.length);

  if (this.length > this._size - o)
    return null;
  this._offset = o;

  var fb = this._buf[this._offset];
  var value = 0;

  for (var i = 0; i < this.length; i++) {
    value <<= 8;
    value |= (this._buf[this._offset++] & 0xff);
  }

  if ((fb & 0x80) === 0x80 && i !== 4)
    value -= (1 << (i * 8));

  return value >> 0;
};



// --- Exported API

module.exports = Reader;