如何在IMFByteStream接口中实现`BeginRead`

using System;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using Windows.Foundation;
using Windows.Media.Core;
using Windows.Media.MediaProperties;
using Windows.Storage.Streams;

public class CustomByteStream : IMFByteStream, IMFAsyncCallback
{
    private IBuffer buffer;
    private uint offset;
    private uint length;
    private bool isReading;

    public CustomByteStream()
    {
        // 初始化缓冲区和其他变量
        buffer = null;
        offset = 0;
        length = 0;
        isReading = false;
    }

    public void BeginRead(byte[] data, int offset, int count, AsyncCallback callback, object state)
    {
        // 将读取请求传递给底层字节流
        // 这里假设底层字节流为stream
        IBuffer readBuffer = new Windows.Storage.Streams.Buffer((uint)count);
        IAsyncOperationWithProgress<IBuffer, uint> readOperation = stream.ReadAsync(readBuffer, (uint)count, InputStreamOptions.None);

        // 设置回调函数
        readOperation.Completed = new AsyncOperationWithProgressCompletedHandler<IBuffer, uint>(ReadCompleted);

        // 存储读取请求的信息
        buffer = readBuffer;
        this.offset = (uint)offset;
        length = (uint)count;
        isReading = true;

        // 调用回调函数处理结果
        callback(this);
    }

    private void ReadCompleted(IAsyncOperationWithProgress<IBuffer, uint> asyncInfo, AsyncStatus asyncStatus)
    {
        if (asyncStatus == AsyncStatus.Completed)
        {
            // 读取成功，将数据存储到缓冲区中
            buffer = asyncInfo.GetResults();

            // 更新偏移量和长度
            offset += buffer.Length;
            length -= buffer.Length;

            // 继续读取剩余的数据
            if (length > 0)
            {
                // 这里假设底层字节流为stream
                IBuffer readBuffer = new Windows.Storage.Streams.Buffer(length);
                IAsyncOperationWithProgress<IBuffer, uint> readOperation = stream.ReadAsync(readBuffer, length, InputStreamOptions.None);
                readOperation.Completed = new AsyncOperationWithProgressCompletedHandler<IBuffer, uint>(ReadCompleted);

                buffer = readBuffer;
                isReading = true;
            }
            else
            {
                // 读取完成，重置状态
                isReading = false;
            }
        }
        else
        {
            // 读取失败，处理错误情况
            // 这里可以根据具体需求进行错误处理
            isReading = false;
        }
    }

    // 其他IMFByteStream接口方法的实现...

    // IMFAsyncCallback接口方法的实现...
}