slab_mutex.h

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#pragma once
// allow-include-after-namespace
 
// IWYU pragma: private

 
#include "fl/stl/noexcept.h"
 
#if defined(ESP32) || defined(ESP_PLATFORM)
 
FL_EXTERN_C_BEGIN
// IWYU pragma: begin_keep
#include "freertos/FreeRTOS.h"
#include "freertos/semphr.h"
#include "freertos/task.h"
// IWYU pragma: end_keep
FL_EXTERN_C_END
 
namespace fl {
namespace detail {
 
class slab_mutex {
  public:
    slab_mutex() FL_NO_EXCEPT : mHandle(xSemaphoreCreateMutex()) {}
    ~slab_mutex() FL_NO_EXCEPT {
        if (mHandle) {
            vSemaphoreDelete(mHandle);
        }
    }
    slab_mutex(const slab_mutex &) FL_NO_EXCEPT = delete;
    slab_mutex &operator=(const slab_mutex &) FL_NO_EXCEPT = delete;
 
    void lock() FL_NO_EXCEPT {
        // Scheduler not running yet (static init) → single-threaded,
        // skip. Never called from ISRs by contract.
        if (mHandle && xTaskGetSchedulerState() == taskSCHEDULER_RUNNING) {
            (void)xSemaphoreTake(mHandle, portMAX_DELAY);
        }
    }
    void unlock() FL_NO_EXCEPT {
        if (mHandle && xTaskGetSchedulerState() == taskSCHEDULER_RUNNING) {
            (void)xSemaphoreGive(mHandle);
        }
    }
 
  private:
    SemaphoreHandle_t mHandle;
};
 
} // namespace detail
} // namespace fl
 
#elif defined(FASTLED_TESTING) || defined(FL_IS_STUB) || defined(_WIN32) || \
    defined(__linux__) || defined(__APPLE__)
 
#include "fl/stl/atomic.h"
 
namespace fl {
namespace detail {

class slab_mutex {
  public:
    slab_mutex() FL_NO_EXCEPT : mFlag(0) {}
    slab_mutex(const slab_mutex &) FL_NO_EXCEPT = delete;
    slab_mutex &operator=(const slab_mutex &) FL_NO_EXCEPT = delete;
 
    void lock() FL_NO_EXCEPT {
        int expected = 0;
        while (!mFlag.compare_exchange_weak(expected, 1)) {
            expected = 0;
        }
    }
    void unlock() FL_NO_EXCEPT { mFlag.store(0); }
 
  private:
    fl::atomic<int> mFlag;
};
 
} // namespace detail
} // namespace fl
 
#else
 
namespace fl {
namespace detail {

class slab_mutex {
  public:
    slab_mutex() FL_NO_EXCEPT = default;
    void lock() FL_NO_EXCEPT {}
    void unlock() FL_NO_EXCEPT {}
};
 
} // namespace detail
} // namespace fl
 
#endif
 
namespace fl {
namespace detail {

class slab_lock_guard {
  public:
    explicit slab_lock_guard(slab_mutex &m) FL_NO_EXCEPT : mMutex(m) {
        mMutex.lock();
    }
    ~slab_lock_guard() FL_NO_EXCEPT { mMutex.unlock(); }
    slab_lock_guard(const slab_lock_guard &) FL_NO_EXCEPT = delete;
    slab_lock_guard &operator=(const slab_lock_guard &) FL_NO_EXCEPT = delete;
 
  private:
    slab_mutex &mMutex;
};
 
} // namespace detail
} // namespace fl