1/**
 2 * Returns a Buffer from a "ff 00 ff"-type hex string.
 3 */
 4
 5getBufferFromHexString = function(byteStr) {
 6  var bytes = byteStr.split(' ');
 7  var buf = new Buffer(bytes.length);
 8  for (var i = 0; i < bytes.length; ++i) {
 9    buf[i] = parseInt(bytes[i], 16);
10  }
11  return buf;
12}
13
14/**
15 * Returns a hex string from a Buffer.
16 */
17
18getHexStringFromBuffer = function(data) {
19  var s = '';
20  for (var i = 0; i < data.length; ++i) {
21    s += padl(data[i].toString(16), 2, '0') + ' ';
22  }
23  return s.trim();
24}
25
26/**
27 * Splits a buffer in two parts.
28 */
29
30splitBuffer = function(buffer) {
31  var b1 = new Buffer(Math.ceil(buffer.length / 2));
32  buffer.copy(b1, 0, 0, b1.length);
33  var b2 = new Buffer(Math.floor(buffer.length / 2));
34  buffer.copy(b2, 0, b1.length, b1.length + b2.length);
35  return [b1, b2];
36}
37
38/**
39 * Performs hybi07+ type masking on a hex string or buffer.
40 */
41
42mask = function(buf, maskString) {
43  if (typeof buf == 'string') buf = new Buffer(buf);
44  var mask = getBufferFromHexString(maskString || '34 83 a8 68');
45  for (var i = 0; i < buf.length; ++i) {
46    buf[i] ^= mask[i % 4];    
47  }
48  return buf;
49}
50
51/**
52 * Returns a hex string representing the length of a message
53 */
54 
55getHybiLengthAsHexString = function(len, masked) {  
56  if (len < 126) {
57    var buf = new Buffer(1);
58    buf[0] = (masked ? 0x80 : 0) | len;
59  }
60  else if (len < 65536) {
61    var buf = new Buffer(3);
62    buf[0] = (masked ? 0x80 : 0) | 126;
63    getBufferFromHexString(pack(4, len)).copy(buf, 1);
64  }
65  else {
66    var buf = new Buffer(9);
67    buf[0] = (masked ? 0x80 : 0) | 127;
68    getBufferFromHexString(pack(16, len)).copy(buf, 1);
69  }
70  return getHexStringFromBuffer(buf);
71}
72
73/**
74 * Unpacks a Buffer into a number.
75 */
76
77unpack = function(buffer) {
78  var n = 0;
79  for (var i = 0; i < buffer.length; ++i) {
80    n = (i == 0) ? buffer[i] : (n * 256) + buffer[i];
81  }
82  return n;
83}
84
85/**
86 * Returns a hex string, representing a specific byte count 'length', from a number.
87 */
88
89pack = function(length, number) {
90  return padl(number.toString(16), length, '0').replace(/([0-9a-f][0-9a-f])/gi, '$1 ').trim();
91}
92
93/**
94 * Left pads the string 's' to a total length of 'n' with char 'c'.
95 */
96
97padl = function(s, n, c) { 
98  return new Array(1 + n - s.length).join(c) + s;
99}