/**
* Returns a Buffer from a "ff 00 ff"-type hex string.
*/
getBufferFromHexString = function(byteStr) {
var bytes = byteStr.split(' ');
var buf = new Buffer(bytes.length);
for (var i = 0; i < bytes.length; ++i) {
buf[i] = parseInt(bytes[i], 16);
}
return buf;
}
/**
* Returns a hex string from a Buffer.
*/
getHexStringFromBuffer = function(data) {
var s = '';
for (var i = 0; i < data.length; ++i) {
s += padl(data[i].toString(16), 2, '0') + ' ';
}
return s.trim();
}
/**
* Splits a buffer in two parts.
*/
splitBuffer = function(buffer) {
var b1 = new Buffer(Math.ceil(buffer.length / 2));
buffer.copy(b1, 0, 0, b1.length);
var b2 = new Buffer(Math.floor(buffer.length / 2));
buffer.copy(b2, 0, b1.length, b1.length + b2.length);
return [b1, b2];
}
/**
* Performs hybi07+ type masking on a hex string or buffer.
*/
mask = function(buf, maskString) {
if (typeof buf == 'string') buf = new Buffer(buf);
var mask = getBufferFromHexString(maskString || '34 83 a8 68');
for (var i = 0; i < buf.length; ++i) {
buf[i] ^= mask[i % 4];
}
return buf;
}
/**
* Returns a hex string representing the length of a message
*/
getHybiLengthAsHexString = function(len, masked) {
if (len < 126) {
var buf = new Buffer(1);
buf[0] = (masked ? 0x80 : 0) | len;
}
else if (len < 65536) {
var buf = new Buffer(3);
buf[0] = (masked ? 0x80 : 0) | 126;
getBufferFromHexString(pack(4, len)).copy(buf, 1);
}
else {
var buf = new Buffer(9);
buf[0] = (masked ? 0x80 : 0) | 127;
getBufferFromHexString(pack(16, len)).copy(buf, 1);
}
return getHexStringFromBuffer(buf);
}
/**
* Unpacks a Buffer into a number.
*/
unpack = function(buffer) {
var n = 0;
for (var i = 0; i < buffer.length; ++i) {
n = (i == 0) ? buffer[i] : (n * 256) + buffer[i];
}
return n;
}
/**
* Returns a hex string, representing a specific byte count 'length', from a number.
*/
pack = function(length, number) {
return padl(number.toString(16), length, '0').replace(/([0-9a-f][0-9a-f])/gi, '$1 ').trim();
}
/**
* Left pads the string 's' to a total length of 'n' with char 'c'.
*/
padl = function(s, n, c) {
return new Array(1 + n - s.length).join(c) + s;
}
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