Semaphore.h

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/* ========================================
 
  Copyright (C) 2024-2025, Amlal El Mahrouss, licensed under the Apache 2.0 license.
 
======================================== */
 
#pragma once

 
#include <CompilerKit/CompilerKit.h>
#include <KernelKit/Timer.h>
#include <NeKit/Config.h>
 
#define kSemaphoreOwnerIndex (0U)
#define kSemaphoreCountIndex (1U)
 
#define kSemaphoreCount (2U)
 
#define kSemaphoreIncrementOwner(sem) (sem[kSemaphoreOwnerIndex]++)
#define kSemaphoreDecrementOwner(sem) (sem[kSemaphoreOwnerIndex]--)
 
namespace Kernel {
typedef UInt64 SemaphoreArr[kSemaphoreCount];

inline BOOL rtl_sem_is_valid(const SemaphoreArr& sem, UInt64 owner = 0) {
  return sem[kSemaphoreOwnerIndex] == owner && sem[kSemaphoreCountIndex] > 0;
}

inline BOOL rtl_sem_release(SemaphoreArr& sem) {
  sem[kSemaphoreOwnerIndex] = 0;
  sem[kSemaphoreCountIndex] = 0;
 
  return TRUE;
}

inline BOOL rtl_sem_acquire(SemaphoreArr& sem, UInt64 owner) {
  if (!owner) {
    err_global_get() = kErrorInvalidData;
    return FALSE;  // Invalid owner
  }
 
  sem[kSemaphoreOwnerIndex] = owner;
  sem[kSemaphoreCountIndex] = 0;
 
  return TRUE;
}

inline BOOL rtl_sem_wait(SemaphoreArr& sem, UInt64 owner, UInt64 timeout,
                         BOOL* condition = nullptr) {
  if (!rtl_sem_is_valid(sem, owner)) {
    return FALSE;
  }
 
  if (timeout <= 0) {
    err_global_get() = kErrorTimeout;
 
    return FALSE;
  }
 
  if (!condition || *condition) {
    if (sem[kSemaphoreCountIndex] == 0) {
      err_global_get() = kErrorUnavailable;
      return FALSE;
    }
 
    err_global_get() = kErrorSuccess;
    sem[kSemaphoreCountIndex]--;
 
    return TRUE;
  }
 
  HardwareTimer timer(timeout);
  BOOL          ret = timer.Wait();
 
  if (ret) {
    if (!condition || *condition) {
      if (sem[kSemaphoreCountIndex] == 0) {
        err_global_get() = kErrorUnavailable;
        return FALSE;
      }
 
      err_global_get() = kErrorSuccess;
      sem[kSemaphoreCountIndex]--;
 
      return TRUE;
    }
  }
 
  err_global_get() = kErrorTimeout;
 
  return FALSE;  // Failed to acquire semaphore
}
}  // namespace Kernel