如何在C＃中实现IRandomAccessStream？

我想在C＃中实现一个IRandomAccessStream实例（它将返回实时生成的数据）。 该流实际上不需要是可写的或可搜索的，但我想在ReadAsync方法（实际上是IInputStream一部分）中返回我自己的数据。

 public IAsyncOperationWithProgress ReadAsync(IBuffer buffer, uint count, InputStreamOptions options) { throw new NotImplementedException("To be done"); } 

我的两个主要问题是：

1. 如何返回实现IAsyncOperationWithProgress ？ 框架中是否有任何内容可以帮助解决这个问题？
2. 如何将数据写入缓冲区？ IBuffer只有Length和Capacity属性（具体的Buffer类也不再提供）。

Answer 1

如何将字节数组转换为IRandomAccessStream

我发现这篇博客文章，希望这个IRandomAccessStream实现可以成为你的起点。

 class MemoryRandomAccessStream : IRandomAccessStream { private Stream m_InternalStream; public MemoryRandomAccessStream(Stream stream) { this.m_InternalStream = stream; } public MemoryRandomAccessStream(byte[] bytes) { this.m_InternalStream = new MemoryStream(bytes); } public IInputStream GetInputStreamAt(ulong position) { this.m_InternalStream.Seek((long)position, SeekOrigin.Begin); return this.m_InternalStream.AsInputStream(); } public IOutputStream GetOutputStreamAt(ulong position) { this.m_InternalStream.Seek((long)position, SeekOrigin.Begin); return this.m_InternalStream.AsOutputStream(); } public ulong Size { get { return (ulong)this.m_InternalStream.Length; } set { this.m_InternalStream.SetLength((long)value); } } public bool CanRead { get { return true; } } public bool CanWrite { get { return true; } } public IRandomAccessStream CloneStream() { throw new NotSupportedException(); } public ulong Position { get { return (ulong)this.m_InternalStream.Position; } } public void Seek(ulong position) { this.m_InternalStream.Seek((long)position, 0); } public void Dispose() { this.m_InternalStream.Dispose(); } public Windows.Foundation.IAsyncOperationWithProgress ReadAsync(IBuffer buffer, uint count, InputStreamOptions options) { var inputStream = this.GetInputStreamAt(0); return inputStream.ReadAsync(buffer, count, options); } public Windows.Foundation.IAsyncOperation FlushAsync() { var outputStream = this.GetOutputStreamAt(0); return outputStream.FlushAsync(); } public Windows.Foundation.IAsyncOperationWithProgress WriteAsync(IBuffer buffer) { var outputStream = this.GetOutputStreamAt(0); return outputStream.WriteAsync(buffer); } } 

Answer 2

1. 使用AsyncInfo.Run(Func, Task>)方法从委托创建IAsyncOperationWithProgress实例。

    public IAsyncOperationWithProgress ReadAsync(IBuffer buffer, uint count, InputStreamOptions options) { if (buffer == null) throw new ArgumentNullException("buffer"); Func, Task> taskProvider = (token, progress) => ReadBytesAsync(buffer, count, token, progress, options); return AsyncInfo.Run(taskProvider); } private async Task ReadBytesAsync(IBuffer buffer, uint count, CancellationToken token, IProgress progress, InputStreamOptions options) { ... Fill the buffer here. Report the progress. return buffer; } 

2. 通常您不需要直接访问缓冲区数据。 但是如果您需要在c＃中执行此操作，则可以使用System.Runtime.InteropServices.WindowsRuntime.WindowsRuntimeBufferExtensions类将数据复制到缓冲区或从缓冲区复制数据。