ClickHouse/src/Common/randomSeed.cpp
2020-04-03 18:14:31 +03:00

34 lines
729 B
C++

#include <time.h>
#include <unistd.h>
#include <sys/types.h>
#include <Common/Exception.h>
#include <Common/randomSeed.h>
#include <Common/SipHash.h>
#include <Core/Types.h>
namespace DB
{
namespace ErrorCodes
{
extern const int CANNOT_CLOCK_GETTIME;
}
}
DB::UInt64 randomSeed()
{
struct timespec times;
if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &times))
DB::throwFromErrno("Cannot clock_gettime.", DB::ErrorCodes::CANNOT_CLOCK_GETTIME);
/// Not cryptographically secure as time, pid and stack address can be predictable.
SipHash hash;
hash.update(times.tv_nsec);
hash.update(times.tv_sec);
hash.update(getpid());
hash.update(&times);
return hash.get64();
}