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// Copyright 2020 The Pigweed 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 "pw_sync/binary_semaphore.h"
#include <algorithm>
#include "FreeRTOS.h"
#include "pw_assert/check.h"
#include "pw_chrono/system_clock.h"
#include "pw_chrono_freertos/system_clock_constants.h"
#include "pw_interrupt/context.h"
#include "semphr.h"
using pw::chrono::SystemClock;
namespace pw::sync {
namespace {
static_assert(configSUPPORT_STATIC_ALLOCATION != 0,
"FreeRTOS static allocations are required for this backend.");
} // namespace
bool BinarySemaphore::try_acquire_for(SystemClock::duration timeout) {
// Enforce the pw::sync::BinarySemaphore IRQ contract.
PW_DCHECK(!interrupt::InInterruptContext());
// Use non-blocking try_acquire for negative and zero length durations.
if (timeout <= SystemClock::duration::zero()) {
return try_acquire();
}
// In case the timeout is too long for us to express through the native
// FreeRTOS API, we repeatedly wait with shorter durations. Note that on a
// tick based kernel we cannot tell how far along we are on the current tick,
// ergo we add one whole tick to the final duration. However, this also means
// that the loop must ensure that timeout + 1 is less than the max timeout.
constexpr SystemClock::duration kMaxTimeoutMinusOne =
pw::chrono::freertos::kMaxTimeout - SystemClock::duration(1);
while (timeout > kMaxTimeoutMinusOne) {
if (xSemaphoreTake(reinterpret_cast<SemaphoreHandle_t>(&native_type_),
static_cast<TickType_t>(kMaxTimeoutMinusOne.count())) ==
pdTRUE) {
return true;
}
timeout -= kMaxTimeoutMinusOne;
}
// On a tick based kernel we cannot tell how far along we are on the current
// tick, ergo we add one whole tick to the final duration.
return xSemaphoreTake(reinterpret_cast<SemaphoreHandle_t>(&native_type_),
static_cast<TickType_t>(timeout.count() + 1)) == pdTRUE;
}
} // namespace pw::sync
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