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// Copyright 2023 The Abseil Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "absl/synchronization/internal/kernel_timeout.h"
#include <algorithm>
#include <cstdint>
#include <ctime>
#include <limits>
#include "absl/base/config.h"
#include "absl/time/time.h"
namespace absl {
ABSL_NAMESPACE_BEGIN
namespace synchronization_internal {
#ifdef ABSL_INTERNAL_NEED_REDUNDANT_CONSTEXPR_DECL
constexpr uint64_t KernelTimeout::kNoTimeout;
constexpr int64_t KernelTimeout::kMaxNanos;
#endif
KernelTimeout::KernelTimeout(absl::Time t) {
// `absl::InfiniteFuture()` is a common "no timeout" value and cheaper to
// compare than convert.
if (t == absl::InfiniteFuture()) {
rep_ = kNoTimeout;
return;
}
int64_t unix_nanos = absl::ToUnixNanos(t);
// A timeout that lands before the unix epoch is converted to 0.
// In theory implementations should expire these timeouts immediately.
if (unix_nanos < 0) {
unix_nanos = 0;
}
// Values greater than or equal to kMaxNanos are converted to infinite.
if (unix_nanos >= kMaxNanos) {
rep_ = kNoTimeout;
return;
}
rep_ = static_cast<uint64_t>(unix_nanos) << 1;
}
KernelTimeout::KernelTimeout(absl::Duration d) {
// `absl::InfiniteDuration()` is a common "no timeout" value and cheaper to
// compare than convert.
if (d == absl::InfiniteDuration()) {
rep_ = kNoTimeout;
return;
}
int64_t nanos = absl::ToInt64Nanoseconds(d);
// Negative durations are normalized to 0.
// In theory implementations should expire these timeouts immediately.
if (nanos < 0) {
nanos = 0;
}
// Values greater than or equal to kMaxNanos are converted to infinite.
if (nanos >= kMaxNanos) {
rep_ = kNoTimeout;
return;
}
rep_ = (static_cast<uint64_t>(nanos) << 1) | uint64_t{1};
}
int64_t KernelTimeout::MakeAbsNanos() const {
if (!has_timeout()) {
return kMaxNanos;
}
int64_t nanos = RawNanos();
if (is_relative_timeout()) {
int64_t now = ToUnixNanos(absl::Now());
if (nanos > kMaxNanos - now) {
// Overflow.
nanos = kMaxNanos;
} else {
nanos += now;
}
} else if (nanos == 0) {
// Some callers have assumed that 0 means no timeout, so instead we return a
// time of 1 nanosecond after the epoch.
nanos = 1;
}
return nanos;
}
struct timespec KernelTimeout::MakeAbsTimespec() const {
return absl::ToTimespec(absl::Nanoseconds(MakeAbsNanos()));
}
struct timespec KernelTimeout::MakeRelativeTimespec() const {
if (!has_timeout()) {
return absl::ToTimespec(absl::Nanoseconds(kMaxNanos));
}
if (is_relative_timeout()) {
return absl::ToTimespec(absl::Nanoseconds(RawNanos()));
}
int64_t nanos = RawNanos();
int64_t now = ToUnixNanos(absl::Now());
if (now > nanos) {
// Convert past values to 0 to be safe.
nanos = 0;
} else {
nanos -= now;
}
return absl::ToTimespec(absl::Nanoseconds(nanos));
}
KernelTimeout::DWord KernelTimeout::InMillisecondsFromNow() const {
constexpr DWord kInfinite = std::numeric_limits<DWord>::max();
if (!has_timeout()) {
return kInfinite;
}
const int64_t nanos = RawNanos();
constexpr uint64_t kNanosInMillis = uint64_t{1000000};
if (is_relative_timeout()) {
uint64_t ms = static_cast<uint64_t>(nanos) / kNanosInMillis;
if (ms > static_cast<uint64_t>(kInfinite)) {
ms = static_cast<uint64_t>(kInfinite);
}
return static_cast<DWord>(ms);
}
int64_t now = ToUnixNanos(absl::Now());
if (nanos >= now) {
// Round up so that now + ms_from_now >= nanos.
constexpr uint64_t kMaxValueNanos =
std::numeric_limits<int64_t>::max() - kNanosInMillis + 1;
uint64_t ms_from_now =
(std::min(kMaxValueNanos, static_cast<uint64_t>(nanos - now)) +
kNanosInMillis - 1) /
kNanosInMillis;
if (ms_from_now > kInfinite) {
return kInfinite;
}
return static_cast<DWord>(ms_from_now);
}
return DWord{0};
}
} // namespace synchronization_internal
ABSL_NAMESPACE_END
} // namespace absl
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