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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "CrossProcessSemaphore.h"
#include "nsDebug.h"
#include "nsISupportsImpl.h"
#include <mach/mach_time.h>
static const uint64_t kNsPerUs = 1000;
static const uint64_t kNsPerSec = 1000000000;
namespace mozilla {
/* static */
CrossProcessSemaphore* CrossProcessSemaphore::Create(const char*,
uint32_t aInitialValue) {
semaphore_t sem = SEMAPHORE_NULL;
if (semaphore_create(mach_task_self(), &sem, SYNC_POLICY_FIFO,
aInitialValue) == KERN_SUCCESS &&
sem != SEMAPHORE_NULL) {
return new CrossProcessSemaphore(CrossProcessSemaphoreHandle(sem));
}
return nullptr;
}
/* static */
CrossProcessSemaphore* CrossProcessSemaphore::Create(
CrossProcessSemaphoreHandle aHandle) {
if (!aHandle) {
return nullptr;
}
return new CrossProcessSemaphore(std::move(aHandle));
}
CrossProcessSemaphore::CrossProcessSemaphore(
CrossProcessSemaphoreHandle aSemaphore)
: mSemaphore(std::move(aSemaphore)) {
MOZ_COUNT_CTOR(CrossProcessSemaphore);
}
CrossProcessSemaphore::~CrossProcessSemaphore() {
MOZ_ASSERT(mSemaphore, "Improper construction of semaphore or double free.");
MOZ_COUNT_DTOR(CrossProcessSemaphore);
}
bool CrossProcessSemaphore::Wait(const Maybe<TimeDuration>& aWaitTime) {
MOZ_ASSERT(mSemaphore, "Improper construction of semaphore.");
int kr = KERN_OPERATION_TIMED_OUT;
// semaphore_(timed)wait may be interrupted by KERN_ABORTED. Carefully restart
// the wait until it either succeeds or times out.
if (aWaitTime.isNothing()) {
do {
kr = semaphore_wait(mSemaphore.get());
} while (kr == KERN_ABORTED);
} else {
mach_timebase_info_data_t tb;
if (mach_timebase_info(&tb) != KERN_SUCCESS) {
return false;
}
uint64_t now = (mach_absolute_time() * tb.numer) / tb.denom;
uint64_t deadline = now + uint64_t(kNsPerUs * aWaitTime->ToMicroseconds());
while (now <= deadline) {
uint64_t ns = deadline - now;
mach_timespec_t ts;
ts.tv_sec = ns / kNsPerSec;
ts.tv_nsec = ns % kNsPerSec;
kr = semaphore_timedwait(mSemaphore.get(), ts);
if (kr != KERN_ABORTED) {
break;
}
now = (mach_absolute_time() * tb.numer) / tb.denom;
}
}
return kr == KERN_SUCCESS;
}
void CrossProcessSemaphore::Signal() {
MOZ_ASSERT(mSemaphore, "Improper construction of semaphore.");
semaphore_signal(mSemaphore.get());
}
CrossProcessSemaphoreHandle CrossProcessSemaphore::CloneHandle() {
// Transfer the mach port backing the semaphore.
return mozilla::RetainMachSendRight(mSemaphore.get());
}
void CrossProcessSemaphore::CloseHandle() {}
} // namespace mozilla
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