overleaf/services/real-time/socket.io.patch.js

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var io = require("socket.io");
if (io.version === "0.9.16") {
console.log("patching socket.io hybi-16 transport frame prototype");
var transports = require("socket.io/lib/transports/websocket/hybi-16.js");
transports.prototype.frame = patchedFrameHandler;
// file hybi-07-12 has the same problem but no browsers are using that protocol now
}
function patchedFrameHandler(opcode, str) {
var dataBuffer = new Buffer(str),
dataLength = dataBuffer.length,
startOffset = 2,
secondByte = dataLength;
if (dataLength === 65536) {
console.log("fixing invalid frame length in socket.io");
}
if (dataLength > 65535) {
// original code had > 65536
startOffset = 10;
secondByte = 127;
} else if (dataLength > 125) {
startOffset = 4;
secondByte = 126;
}
var outputBuffer = new Buffer(dataLength + startOffset);
outputBuffer[0] = opcode;
outputBuffer[1] = secondByte;
dataBuffer.copy(outputBuffer, startOffset);
switch (secondByte) {
case 126:
outputBuffer[2] = dataLength >>> 8;
outputBuffer[3] = dataLength % 256;
break;
case 127:
var l = dataLength;
for (var i = 1; i <= 8; ++i) {
outputBuffer[startOffset - i] = l & 0xff;
l >>>= 8;
}
}
return outputBuffer;
}