IrqEventCounter.h

/*
 * Copyright (c) 2026, Pedigree Developers
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted.
 */
 
#ifndef PEDIGREE_KERNEL_MACHINE_IRQEVENTCOUNTER_H
#define PEDIGREE_KERNEL_MACHINE_IRQEVENTCOUNTER_H
#include "pedigree/kernel/Atomic.h"
#include "pedigree/kernel/processor/types.h"
 
#include <config.h>
 
class IrqEventCounter {
 public:
  IrqEventCounter() : m_Count(0) {}
 
  bool recordFromInterrupt(size_t occurrences = 1) {
    if (!occurrences) {
      return true;
    }
 
    constexpr size_t Maximum = ~static_cast<size_t>(0);
    const size_t count = m_Count.value();
    if (occurrences > (Maximum - count)) {
      return false;
    }
 
    // There is one hard producer. A concurrent consumer can only reset
    // the counter to zero, which creates capacity rather than invalidating
    // this preflight check.
    m_Count += occurrences;
    return true;
  }
 
  size_t takeAll() {
    size_t count = m_Count.value();
    while (count && !m_Count.compareAndSwap(count, 0)) {
      count = m_Count.value();
    }
    return count;
  }
 
  bool pending() const {
    return m_Count.value() != 0;
  }
 
  void reset() {
    m_Count = 0;
  }
 
 private:
  Atomic<size_t> m_Count;
 
  IrqEventCounter(const IrqEventCounter&) = delete;
  IrqEventCounter& operator=(const IrqEventCounter&) = delete;
};
 
#endif