| // 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. |
| #pragma once |
| |
| #include <stddef.h> |
| |
| #include "pw_chrono/system_clock.h" |
| #include "pw_preprocessor/util.h" |
| |
| #ifdef __cplusplus |
| |
| #include "pw_sync_backend/binary_semaphore_native.h" |
| |
| namespace pw::sync { |
| |
| // BinarySemaphore is a specialization of CountingSemaphore with arbitrary |
| // token limit of 1. Note that that max() is >= 1, meaning it may be |
| // released up to max() times but only acquired once for those N releases. |
| // Implementations of BinarySemaphore are typically more efficient than the |
| // default implementation of CountingSemaphore. The entire API is thread safe |
| // but only a subset is IRQ safe. |
| // |
| // WARNING: In order to support global statically constructed BinarySemaphores, |
| // the backend MUST ensure that any initialization required in your environment |
| // prior to the creation and/or initialization of the native semaphore |
| // (e.g. kernel initialization), is done before or during the invocation of the |
| // global static C++ constructors. |
| class BinarySemaphore { |
| public: |
| using native_handle_type = backend::NativeBinarySemaphoreHandle; |
| |
| BinarySemaphore(); |
| ~BinarySemaphore(); |
| BinarySemaphore(const BinarySemaphore&) = delete; |
| BinarySemaphore(BinarySemaphore&&) = delete; |
| BinarySemaphore& operator=(const BinarySemaphore&) = delete; |
| BinarySemaphore& operator=(BinarySemaphore&&) = delete; |
| |
| // Atomically increments the internal counter by 1 up to max_count. |
| // Any thread(s) waiting for the counter to be greater than 0, |
| // such as due to being blocked in acquire, will subsequently be unblocked. |
| // This is IRQ safe. |
| // |
| // PRECONDITIONS: |
| // 1 <= max() - counter |
| void release(); |
| |
| // Decrements the internal counter to 0 or blocks indefinitely until it can. |
| // This is thread safe. |
| |
| // update <= max() - counter |
| void acquire(); |
| |
| // Attempts to decrement by the internal counter to 0 without blocking. |
| // Returns true if the internal counter was reset successfully. |
| // This is IRQ safe. |
| bool try_acquire() noexcept; |
| |
| // Attempts to decrement the internal counter to 0 where, if needed, blocking |
| // for at least the specified duration. |
| // Returns true if the internal counter was decremented successfully. |
| // This is thread safe. |
| bool try_acquire_for(chrono::SystemClock::duration for_at_least); |
| |
| // Attempts to decrement the internal counter to 0 where, if needed, blocking |
| // until at least the specified time point. |
| // Returns true if the internal counter was decremented successfully. |
| // This is thread safe. |
| bool try_acquire_until(chrono::SystemClock::time_point until_at_least); |
| |
| static constexpr ptrdiff_t max() noexcept { |
| return backend::kBinarySemaphoreMaxValue; |
| } |
| |
| native_handle_type native_handle(); |
| |
| private: |
| // This may be a wrapper around a native type with additional members. |
| backend::NativeBinarySemaphore native_type_; |
| }; |
| |
| } // namespace pw::sync |
| |
| #include "pw_sync_backend/binary_semaphore_inline.h" |
| |
| using pw_sync_BinarySemaphore = pw::sync::BinarySemaphore; |
| |
| #else // !defined(__cplusplus) |
| |
| typedef struct pw_sync_BinarySemaphore pw_sync_BinarySemaphore; |
| |
| #endif // __cplusplus |
| |
| PW_EXTERN_C_START |
| |
| void pw_sync_BinarySemaphore_Release(pw_sync_BinarySemaphore* semaphore); |
| void pw_sync_BinarySemaphore_Acquire(pw_sync_BinarySemaphore* semaphore); |
| bool pw_sync_BinarySemaphore_TryAcquire(pw_sync_BinarySemaphore* semaphore); |
| bool pw_sync_BinarySemaphore_TryAcquireFor( |
| pw_sync_BinarySemaphore* semaphore, |
| pw_chrono_SystemClock_TickCount for_at_least); |
| bool pw_sync_BinarySemaphore_TryAcquireUntil( |
| pw_sync_BinarySemaphore* semaphore, |
| pw_chrono_SystemClock_TimePoint until_at_least); |
| ptrdiff_t pw_sync_BinarySemaphore_Max(void); |
| |
| PW_EXTERN_C_END |