What is the best way to programmatically generate a GUID or UUID in C++ without relying on a platform-specific tool? I am trying to make unique identifiers for objects in a simulation, but can't rely on Microsoft's implementation as the project is cross-platform.
Notes:
A GUID generator usually relies on hardware characteristics of the machine, usually stuff like MAC addresses or IPs. The only thing you can do which is absolutely platform independent is use some kind of PRNG seeded manually or seeded from some time source. This usually does not generate a true globally unique identifier in the sense that you are guaranteed that no one in the world generates the same number.
Simply using whatever guid/uuid is present on the target platform is best. Doing it right is hard (let's go shopping ;)).
The probability of a collision between any two identifiers from different but well executed implementations should be well beyond any reasonable chance of happening in this universe's lifetime.
Recently Boost held the mini-review for the UUID library. It had been accepted, but there are few minor quirks to fix.
If you don't mind some reading the review itself can give quite a good overview of the UUID related problems and possible solutions.
Well one offbeat(?) solution would be to use a web service to get the GUID but I doubt this will be a good solution for a C++ program especially if it's not network enabled.
Here is a URL which might come in handy if you choose to pursue this option: http://www.hoskinson.net/GuidGenerator/default.asp
on linux: man uuid
on win: check out for UUID structure and UuidCreate function in msdn
[edit] the function would appear like this
extern "C"
{
#ifdef WIN32
#include <Rpc.h>
#else
#include <uuid/uuid.h>
#endif
}
std::string newUUID()
{
#ifdef WIN32
UUID uuid;
UuidCreate ( &uuid );
unsigned char * str;
UuidToStringA ( &uuid, &str );
std::string s( ( char* ) str );
RpcStringFreeA ( &str );
#else
uuid_t uuid;
uuid_generate_random ( uuid );
char s[37];
uuid_unparse ( uuid, s );
#endif
return s;
}