This is xnu-8019. See this file in:
/*
 * Copyright (c) 2019-2019 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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#ifndef _IOKIT_UIODATAQUEUEDISPATCHSOURCE_H
#define _IOKIT_UIODATAQUEUEDISPATCHSOURCE_H

#include <DriverKit/IODispatchQueue.iig>
#include <DriverKit/IOMemoryDescriptor.iig>

typedef void (^IODataQueueClientEnqueueEntryBlock)(void *data, size_t dataSize);
typedef void (^IODataQueueClientDequeueEntryBlock)(const void *data, size_t dataSize);

class NATIVE KERNEL IODataQueueDispatchSource : public IODispatchSource
{
public:

    /*!
     * @brief       Create an IODataQueueDispatchSource for a shared memory data queue.
     * @param       queueByteCount The size of the queue in bytes.
     * @param       queue IODispatchQueue the source is attached to. Note that the DataAvailable
     *              and DataServiced handlers are invoked on the queue set for the target method
     *              of the OSAction, not this queue.
     * @param       source Created source with +1 retain count to be released by the caller.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
	static kern_return_t
	Create(
		uint64_t queueByteCount,
	    IODispatchQueue * queue,
	    IODataQueueDispatchSource ** source);

	virtual bool
	init() override;

	virtual void
	free() override;

    /*!
     * @brief       As a consumer, set the handler block to run when the queue becomes non-empty.
     * @param       action OSAction instance specifying the callback method. The OSAction object will be retained
     *              until SetHandler is called again or the event source is cancelled.
     *              The DataAvailable handler is invoked on the queue set for the target method of the OSAction.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
	virtual kern_return_t
	SetDataAvailableHandler(
	OSAction * action TYPE(DataAvailable));

    /*!
     * @brief       As a producer, set the handler block to run when the queue becomes non-full, after an attempt
     *              to enqueue data failed.
     * @param       action OSAction instance specifying the callback method. The OSAction object will be retained
     *              until SetHandler is called again or the event source is cancelled.
     *              The DataServiced handler is invoked on the queue set for the target method of the OSAction.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
	virtual kern_return_t
	SetDataServicedHandler(
	OSAction * action TYPE(DataServiced));

    /*!
     * @brief       Control the enable state of the interrupt source.
     * @param       enable Pass true to enable the source or false to disable.
     * @param       handler Optional block to be executed after the interrupt has been disabled and any pending
     *              interrupt handlers completed.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
	virtual kern_return_t
	SetEnableWithCompletion(
		bool enable,
		IODispatchSourceCancelHandler handler) override LOCAL;

    /*!
     * @brief       Cancel all callbacks from the event source.
     * @discussion  After cancellation, the source can only be freed. It cannot be reactivated.
     * @param       handler Handler block to be invoked after any callbacks have completed.
     * @return      kIOReturnSuccess on success. See IOReturn.h for error codes.
     */
	virtual kern_return_t
	Cancel(IODispatchSourceCancelHandler handler) override LOCAL;


    /*!
     * @brief       As a consumer, check if the data queue is non-empty.
     * @return      True if the queue is non-empty.
     */
	bool
	IsDataAvailable(void) LOCALONLY;

    /*!
     * @brief       As a consumer, get access to the next queue entry without dequeuing it.
     * @param       callback to invoked if the queue is non-empty with the next entry to be dequeued.
     * @return      kIOReturnSuccess if the callback was invoked.
     *              kIOReturnUnderrun if the queue was empty.
     *              kIOReturnError if the queue was corrupt.
     */
	kern_return_t
	Peek(IODataQueueClientDequeueEntryBlock callback) LOCALONLY;

    /*!
     * @brief       As a consumer, dequeue the next queue entry.
     * @param       callback invoked if the queue was non-empty with the entry that was dequeued.
     * @return      kIOReturnSuccess if the callback was invoked.
     *              kIOReturnUnderrun if the queue was empty.
     *              kIOReturnError if the queue was corrupt.
     */
	kern_return_t
	Dequeue(IODataQueueClientDequeueEntryBlock callback) LOCALONLY;

    /*!
     * @brief       As a producer, enqueue a queue entry.
     * @param       dataSize size of the data to enqueue.
     * @param       callback invoked if the queue has enough space to enqueue the data.
     * @return      kIOReturnSuccess if the callback was invoked.
     *              kIOReturnOverrun if the queue was full.
     *              kIOReturnError if the queue was corrupt.
     */
	kern_return_t
	Enqueue(uint32_t dataSize, IODataQueueClientEnqueueEntryBlock callback) LOCALONLY;

    /*!
     * @brief       As a consumer, dequeue the next queue entry, but don't send any DataServiced notification.
     * @param       sendDataServiced Flag that indicates a DataServiced notification would have sent.
     *              It should be initialized to false before a series of calls to this method,
     *              and if true after those calls, the notification sent with SendDataServiced().
     * @param       callback invoked if the queue was non-empty with the entry that was dequeued.
     * @return      kIOReturnSuccess if the callback was invoked.
     *              kIOReturnUnderrun if the queue was empty.
     *              kIOReturnError if the queue was corrupt.
     */
	kern_return_t
	DequeueWithCoalesce(bool * sendDataServiced, IODataQueueClientDequeueEntryBlock callback) LOCALONLY;

    /*!
     * @brief       As a producer, enqueue a queue entry, but don't send any DataAvailable notification.
     * @param       dataSize size of the data to enqueue
     * @param       sendDataAvailable Flag that indicates a DataAvailable notification would have been sent.
     *              It should be initialized to false before a series of calls to this method,
     *              and if true after those calls, the notification sent with SendDataAvailable().
     * @param       callback invoked if the queue has enough space to enqueue the data.
     * @return      kIOReturnSuccess if the callback was invoked.
     *              kIOReturnOverrun if the queue was full.
     *              kIOReturnError if the queue was corrupt.
     */
	kern_return_t
	EnqueueWithCoalesce(uint32_t dataSize,  bool * sendDataAvailable, IODataQueueClientEnqueueEntryBlock callback) LOCALONLY;

    /*!
     * @brief       As a consumer, send the DataServiced notification indicated by DequeueWithCoalesce.
	 */
	void
	SendDataServiced(void) LOCALONLY;

    /*!
     * @brief       As a producer, send the DataAvailable notification indicated by EnqueueWithCoalesce.
	 */
	void
	SendDataAvailable(void) LOCALONLY;

private:
	virtual kern_return_t
	CopyMemory(
	IOMemoryDescriptor ** memory);

	virtual kern_return_t
	CopyDataAvailableHandler(
	OSAction ** action);

	virtual kern_return_t
	CopyDataServicedHandler(
	OSAction ** action);

	virtual kern_return_t
	CheckForWork(bool synchronous) override LOCAL;

	virtual void
	DataAvailable(
		OSAction * action TARGET) LOCAL = 0;

	virtual void
	DataServiced(
		OSAction * action TARGET) LOCAL = 0;
};

#endif /* ! _IOKIT_UIODATAQUEUEDISPATCHSOURCE_H */