method writeInt64

This method writes a signed 64 bit number to the stream and advance the stream's position. If the write fails, then the stream's position is unaffected.

var fileStreamObj = shell.serviceManager.basics.fileStream;
var streamWriterObj = shell.serviceManager.basics.rawStreamWriter;

fileStreamObj.openForWrite("c:\\temp\\test.txt", false, true);
streamWriterObj.stream = fileStreamObj;
streamWriterObj.writeInt64(1024*1024*1024);
streamWriterObj.writeInt64(-1* 1024*1024*512);

fileStreamObj.close();