// file <input type="file"> element
        // policy - from the previous post
        // process - function() // callback
        // complete - function() // when its done
        function upload(file, policy, progress, complete) {

            var xhr = new XMLHttpRequest()

            var formdata = new FormData()

            formdata.append('key', policy.path)

            formdata.append('AWSAccessKeyId', policy.accesskey)

            formdata.append('acl', policy.acl)

            formdata.append('policy', policy.policy)

            formdata.append('signature', policy.signature)

            formdata.append('file', file)

            xhr.upload.addEventListener('progress', function(e) {

                if(progress) {

                    progress({

                        total : file.size,

                        sent : e.loaded,

                        percent : Math.round((e.loaded * 100) / e.total),

                        value : (e.loaded / e.total)

                    })

                }

            }, false)

            xhr.onreadystatechange = function() {

                if (xhr.readyState == 4) {

                    if(complete) {

                        complete()

                    }

                    return;
                }
            }
            xhr.open("POST", "https://s3.amazonaws.com/" + policy.bucket + "/", true)

            xhr.send(formdata)
        }