Want to use prepared buffer with `Array#pack`
Array#pack always returns new allocated
String, but sometimes users want to use prepared buffer, especially the packed size is too large.
I often uses
Fiddle to call OS APIs, and encounter this problem as every time.
I recommend to add keyword arguments for the purpose.
buf = '\0'*(32 * 1024 * 1024) # ... ary.pack(LONG_FORMAT, buffer: buf, offset: 4 * 1024) # returns `buf`