DouKaku?

var lk1 = new java.util.concurrent.locks.ReentrantLock();
var lk2 = new java.util.concurrent.locks.ReentrantLock();
var queue1 = [];
var queue2 = [];
var eof = false;
var eop = false;
var infile = arguments[0];
var outfile = arguments[1];

spawn(function() {
    var input = new java.io.BufferedReader(new java.io.FileReader(new java.io.File(infile)));
    var line;
    try {
        while (line = input.readLine()) {
            lk1.lock();
            try {
                queue1.push(line);
            }
            finally {
                lk1.unlock();
            }
        }
    }
    finally {
        eof = true;
        input.close();
    }
});

spawn(function() {
    try {
out:
        while (true) {
            lk1.lock();
            try {
                while (queue1.length == 0) {
                    if (eof) break out;
                    lk1.unlock();
                    lk1.lock();
                }
                var line = queue1.shift();
            }
            finally {
                lk1.unlock();
            }
            var m = line.match(/^(\d+\.\d+\.\d+\.\d+)(.*)$/);
            if (m) {
                line = java.net.InetAddress.getByName(m[1]).getHostName() + m[2];
            }
            lk2.lock();
            try {
                queue2.push(line);
            }
            finally {
                lk2.unlock();
            }
        }
    }
    finally {
        eop = true;
    }
});

spawn(function() {
    var output = new java.io.PrintWriter(new java.io.File(outfile));
    try {
out:
        while (true) {
            lk2.lock();
            try {
                while (queue2.length == 0) {
                    if (eop) break out;
                    lk2.unlock();
                    lk2.lock();
                }
                var line = queue2.shift();
            }
            finally {
                lk2.unlock();
            }
            output.println(line);
        }
    }
    finally {
        output.close();
    }
});