Function NUM2ULONG 

pub unsafe fn NUM2ULONG(obj: VALUE) -> c_ulong

Convert Ruby Integer to unsigned long (akin to NUM2ULONG).

Converts any Ruby Integer (Fixnum or Bignum) to a C unsigned long. May raise a RangeError exception if the value is out of range or negative.

Safety

• obj must be a valid Integer VALUE
• May call into Ruby runtime and potentially raise exceptions
• May trigger garbage collection