RingBuffer.h

/*
 * Copyright (c) 2008-2014, Pedigree Developers
 *
 * Please see the CONTRIB file in the root of the source tree for a full
 * list of contributors.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
 
#ifndef RINGBUFFER_H
#define RINGBUFFER_H
#include "pedigree/kernel/Atomic.h"
#include "pedigree/kernel/process/Event.h"
#include "pedigree/kernel/process/Semaphore.h"
#include "pedigree/kernel/process/Thread.h"
#include "pedigree/kernel/utilities/BufferMonitors.h"
#include "pedigree/kernel/utilities/Mailbox.h"
 
namespace RingBufferWait = MailboxWait;
 
struct RingBufferNotifications {
  void changed(bool becameReadable, bool becameWritable) {
    if (becameReadable) {
      readableGeneration += 1;
    }
    if (becameWritable) {
      writableGeneration += 1;
    }
    monitors.notify();
  }
 
  void closed() {
    monitors.notify();
  }
 
  Atomic<uint64_t> readableGeneration{0};
  Atomic<uint64_t> writableGeneration{0};
  BufferMonitors monitors;
};
 
template <class T, size_t preallocatedSize = 0>
class EXPORTED_PUBLIC RingBuffer : public Mailbox<T, preallocatedSize, RingBufferNotifications> {
  using Base = Mailbox<T, preallocatedSize, RingBufferNotifications>;
 
 public:
  explicit RingBuffer(size_t ringSize) : Base(ringSize) {}
 
  uint64_t readableGeneration() const {
    return this->m_Notifications.readableGeneration.value();
  }
 
  uint64_t writableGeneration() const {
    return this->m_Notifications.writableGeneration.value();
  }
 
  bool monitor(Thread* pThread, Event* pEvent) {
    typename Base::ActiveOperation operation(*this);
    if (!operation) {
      Event::SendLease registration;
      if (pEvent->tryAcquireRegistration(registration)) {
        EMIT_IF(THREADS) {
          pThread->sendEvent(pEvent);
        }
      }
      return false;
    }
 
    if (this->readsClosed()) {
      Event::SendLease registration;
      if (pEvent->tryAcquireRegistration(registration)) {
        EMIT_IF(THREADS) {
          pThread->sendEvent(pEvent);
        }
      }
      return false;
    }
 
    return this->m_Notifications.monitors.add(pThread, pEvent);
  }
 
  bool monitor(Semaphore* pSemaphore) {
    typename Base::ActiveOperation operation(*this);
    if (!operation) {
      EMIT_IF(THREADS) {
        pSemaphore->release();
      }
      return false;
    }
 
    if (this->readsClosed()) {
      EMIT_IF(THREADS) {
        pSemaphore->release();
      }
      return false;
    }
 
    this->m_Notifications.monitors.add(pSemaphore);
    return true;
  }
 
  void cullMonitorTargets(Thread* pThread) {
    typename Base::ActiveOperation operation(*this);
    if (!operation) {
      return;
    }
 
    this->m_Notifications.monitors.cull(pThread);
  }
 
  void cullMonitorTargets(Semaphore* pSemaphore) {
    typename Base::ActiveOperation operation(*this);
    if (!operation) {
      return;
    }
 
    this->m_Notifications.monitors.cull(pSemaphore);
  }
 
  void cullMonitorTargets(Event* pEvent) {
    typename Base::ActiveOperation operation(*this);
    if (!operation) {
      return;
    }
 
    this->m_Notifications.monitors.cull(pEvent);
  }
};
 
extern template class RingBuffer<char>;   // IWYU pragma: keep
extern template class RingBuffer<void*>;  // IWYU pragma: keep
 
#endif