var multipart = require("multipart");

// parsing
var parser = multipart.parser();

// in all event handlers, "this" is the parser, and "this.part" is the
// part that's currently being dealt with.
parser.onpartbegin = function (part) { doSomething(part) };
parser.ondata = function (chunk) { doSomethingElse(chunk) };
parser.onend = function () { closeItUp() };

// now start feeding the message through it.
// you can do this all in one go, if you like, or one byte at a time,
// or anything in between.
parser.boundary = "foo";
var chunk;
while ( chunk = upstreamThing.getNextChunk() ) {
  parser.write(chunk);
}
parser.close();


// writing
var writer = multipart.writer();

// attach event handlers for the things we care about.
writer.ondata = function (chunk) { doSomething(chunk) };
writer.onend = function () { closeItUp() };

// now trigger the events to fire by feeding files through it.
writer.boundary = "foo";
writer.partBegin({ "content-type" : "text/plain", filename : "foo.txt" });
var chunk;
while ( chunk = getChunkOfFile() ) {
  writer.write(chunk);
}
writer.partEnd();
writer.close();