stream_reader.js

// I need a better name for the thing below called StreamReader. It essentially
// lets you split a stream into a sequence of smaller streams of fixed size,
// simplifying parsing TCP input for certain protocols.
//
// What it does:
//
// * It's a writable stream that buffers everything written to it
//
// * It has a fork() method, that takes a number n and returns a stream that
//   will yield up to n bytes before emitting 'end', with no guarantees about
//   where the chunk buffer boundaries occur
//
// * When a stream is created with fork(n), if there are no streams ahead of it
//   in the queue, StreamReader routes up to n of its buffered bytes to this
//   new stream
//
// * As new bytes are written, they are routed to the first stream in the queue
//   until that stream has reached its byte limit
//
// * Once a stream reaches its limit it is shifted off the queue and input is
//   routed to the next forked stream

var sr = new StreamReader();

var a = sr.fork(3), b = sr.fork(4), c = sr.fork(5);

a.on('data', function(buf) { console.log('A', buf) });
b.on('data', function(buf) { console.log('B', buf) });
c.on('data', function(buf) { console.log('C', buf) });

var hello = new Buffer('Hello, world');
console.log(hello);

sr.write(hello);

/*  -> <Buffer 48 65 6c 6c 6f 2c 20 77 6f 72 6c 64>
       A <Buffer 48 65 6c>
       B <Buffer 6c 6f 2c 20>
       C <Buffer 77 6f 72 6c 64>
*/