1/*!
  2 * base64id v0.1.0
  3 */
  4
  5/**
  6 * Module dependencies
  7 */
  8
  9var crypto = require('crypto');
 10
 11/**
 12 * Constructor
 13 */
 14
 15var Base64Id = function() { };
 16
 17/**
 18 * Get random bytes
 19 *
 20 * Uses a buffer if available, falls back to crypto.randomBytes
 21 */
 22
 23Base64Id.prototype.getRandomBytes = function(bytes) {
 24
 25  var BUFFER_SIZE = 4096
 26  var self = this;  
 27  
 28  bytes = bytes || 12;
 29
 30  if (bytes > BUFFER_SIZE) {
 31    return crypto.randomBytes(bytes);
 32  }
 33  
 34  var bytesInBuffer = parseInt(BUFFER_SIZE/bytes);
 35  var threshold = parseInt(bytesInBuffer*0.85);
 36
 37  if (!threshold) {
 38    return crypto.randomBytes(bytes);
 39  }
 40
 41  if (this.bytesBufferIndex == null) {
 42     this.bytesBufferIndex = -1;
 43  }
 44
 45  if (this.bytesBufferIndex == bytesInBuffer) {
 46    this.bytesBuffer = null;
 47    this.bytesBufferIndex = -1;
 48  }
 49
 50  // No buffered bytes available or index above threshold
 51  if (this.bytesBufferIndex == -1 || this.bytesBufferIndex > threshold) {
 52     
 53    if (!this.isGeneratingBytes) {
 54      this.isGeneratingBytes = true;
 55      crypto.randomBytes(BUFFER_SIZE, function(err, bytes) {
 56        self.bytesBuffer = bytes;
 57        self.bytesBufferIndex = 0;
 58        self.isGeneratingBytes = false;
 59      }); 
 60    }
 61    
 62    // Fall back to sync call when no buffered bytes are available
 63    if (this.bytesBufferIndex == -1) {
 64      return crypto.randomBytes(bytes);
 65    }
 66  }
 67  
 68  var result = this.bytesBuffer.slice(bytes*this.bytesBufferIndex, bytes*(this.bytesBufferIndex+1)); 
 69  this.bytesBufferIndex++; 
 70  
 71  return result;
 72}
 73
 74/**
 75 * Generates a base64 id
 76 *
 77 * (Original version from socket.io <http://socket.io>)
 78 */
 79
 80Base64Id.prototype.generateId = function () {
 81  var rand = new Buffer(15); // multiple of 3 for base64
 82  if (!rand.writeInt32BE) {
 83    return Math.abs(Math.random() * Math.random() * Date.now() | 0).toString()
 84      + Math.abs(Math.random() * Math.random() * Date.now() | 0).toString();
 85  }
 86  this.sequenceNumber = (this.sequenceNumber + 1) | 0;
 87  rand.writeInt32BE(this.sequenceNumber, 11);
 88  if (crypto.randomBytes) {
 89    this.getRandomBytes(12).copy(rand);
 90  } else {
 91    // not secure for node 0.4
 92    [0, 4, 8].forEach(function(i) {
 93      rand.writeInt32BE(Math.random() * Math.pow(2, 32) | 0, i);
 94    });
 95  }
 96  return rand.toString('base64').replace(/\//g, '_').replace(/\+/g, '-');
 97};
 98
 99/**
100 * Export
101 */
102
103exports = module.exports = new Base64Id();