Question

We have a file that has a 64 bit integer as a string in it. How do we scanf() or otherwise parse this numeric string into an unsigned 64 bit integer type in C++ ?

We are aware of things like %lld etc., but a lot of ways to do this parse seem to break compiles under different compilers and stdlibs. The code should compile under gcc and the Microsoft C++ compiler (of course full compliance with standards would be a plus)

Answer 1

GCC has long long, as will compilers for C++0x. MSVC++ doesn’t (yet), but does have its __int64 you can use.

#if (__cplusplus > 199711L) || defined(__GNUG__)     typedef unsigned long long uint_64_t; #elif defined(_MSC_VER) || defined(__BORLANDC__)      typedef unsigned __int64 uint_64_t; #else #error 'Please define uint_64_t' #endif  uint_64_t foo;  std::fstream fstm( 'file.txt' ); fstm >> foo;