mirror of
https://github.com/kidfromjupiter/nearby.git
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Alexey Polyudov
6b27a508ed
Signed-off-by: Alexey Polyudov <apolyudov@google.com> Change-Id: I4bf367877a986910bb03e1c54aa972b4bcd59942
46 lines
1.2 KiB
C++
46 lines
1.2 KiB
C++
#include "platform_v2/base/prng.h"
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#include <limits>
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#include "absl/time/clock.h"
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namespace location {
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namespace nearby {
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#define UNSIGNED_INT_BITMASK (std::numeric_limits<unsigned int>::max())
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Prng::Prng() {
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// absl::GetCurrentTimeNanos() returns 64 bits, but srand() wants an unsigned
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// int, so we may have to lose some of those 64 bits.
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//
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// The lower bits of the current-time-in-nanos are likely to have more entropy
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// than the upper bits, so choose the former.
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srand(static_cast<unsigned int>(absl::GetCurrentTimeNanos() &
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UNSIGNED_INT_BITMASK));
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}
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Prng::~Prng() {
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// Nothing to do.
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}
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#define RANDOM_BYTE (rand() & 0x0FF) // NOLINT
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std::int32_t Prng::NextInt32() {
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return (static_cast<std::int32_t>(RANDOM_BYTE) << 24) |
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(static_cast<std::int32_t>(RANDOM_BYTE) << 16) |
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(static_cast<std::int32_t>(RANDOM_BYTE) << 8) |
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(static_cast<std::int32_t>(RANDOM_BYTE));
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}
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std::uint32_t Prng::NextUint32() {
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return static_cast<std::uint32_t>(NextInt32());
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}
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std::int64_t Prng::NextInt64() {
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return (static_cast<std::int64_t>(NextInt32()) << 32) |
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(static_cast<std::int64_t>(NextUint32()));
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}
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} // namespace nearby
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} // namespace location
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