//Convert attachment to base 64 string

var gsa = GlideSysAttachmentInputStream('e1d8bd45dbb103006cc25990cf96197b');
var baos = new Packages.java.io.ByteArrayOutputStream();
gsa.writeTo(baos);
var base64Data = GlideStringUtil.base64Encode(baos.toByteArray());

//Convert the string to array chunks with 3736 chars length
function splitString (string, size) {
    var re = new RegExp('.{1,' + size + '}', 'g');
return base64Data.match(re);
}
var myarr = splitString(base64Data,3736);

//Send the array as Json via Rest
var request = new sn_ws.RESTMessageV2();
request.setEndpoint('https://dev24007.service-now.com/api/164669/valerianche');
request.setHttpMethod('POST');

//Eg. UserName="admin", Password="admin" for this code sample.
var user = 'admin';
var password = 'Prohor@73';
request.setBasicAuth(user,password);

//request.setRequestHeader("Accept","application/json");

var obj = {};
obj.payload = myarr;
var attachment = {
      table_name: 'incident',
     table_sys_id: '46ee851edb3103001c917befbf96195c',
     file_size: '3636',
    table: 'incident',
      file_name: 'KOP'
    };
obj.attachment = attachment;


request.setRequestBody(JSON.stringify(obj));
 //gs.log(request.getRequestBody());
request.execute();
var response = request.execute();
gs.log(response.getBody());