mirror of
https://github.com/kidfromjupiter/nearby.git
synced 2026-09-14 22:56:12 -04:00
Alexey Polyudov
204f76077d
Signed-off-by: Alexey Polyudov <apolyudov@google.com> Change-Id: I2cf5bf225b76f4c1541954651f3a7544a14e0cec
46 lines
1.2 KiB
C++
46 lines
1.2 KiB
C++
#include "platform/prng.h"
|
|
|
|
#include <limits>
|
|
|
|
#include "absl/time/clock.h"
|
|
|
|
namespace location {
|
|
namespace nearby {
|
|
|
|
#define UNSIGNED_INT_BITMASK (std::numeric_limits<unsigned int>::max())
|
|
|
|
Prng::Prng() {
|
|
// absl::GetCurrentTimeNanos() returns 64 bits, but srand() wants an unsigned
|
|
// int, so we may have to lose some of those 64 bits.
|
|
//
|
|
// The lower bits of the current-time-in-nanos are likely to have more entropy
|
|
// than the upper bits, so choose the former.
|
|
srand(static_cast<unsigned int>(absl::GetCurrentTimeNanos() &
|
|
UNSIGNED_INT_BITMASK));
|
|
}
|
|
|
|
Prng::~Prng() {
|
|
// Nothing to do.
|
|
}
|
|
|
|
#define RANDOM_BYTE (rand() & 0x0FF) // NOLINT
|
|
|
|
std::int32_t Prng::nextInt32() {
|
|
return (static_cast<std::int32_t>(RANDOM_BYTE) << 24) |
|
|
(static_cast<std::int32_t>(RANDOM_BYTE) << 16) |
|
|
(static_cast<std::int32_t>(RANDOM_BYTE) << 8) |
|
|
(static_cast<std::int32_t>(RANDOM_BYTE));
|
|
}
|
|
|
|
std::uint32_t Prng::nextUInt32() {
|
|
return static_cast<std::uint32_t>(nextInt32());
|
|
}
|
|
|
|
std::int64_t Prng::nextInt64() {
|
|
return (static_cast<std::int64_t>(nextInt32()) << 32) |
|
|
(static_cast<std::int64_t>(nextInt32()));
|
|
}
|
|
|
|
} // namespace nearby
|
|
} // namespace location
|