WrappingAsyncStream.cs

// Copyright (C) 2025, The Duplicati Team
// https://duplicati.com, hello@duplicati.com
// 
// Permission is hereby granted, free of charge, to any person obtaining a 
// copy of this software and associated documentation files (the "Software"), 
// to deal in the Software without restriction, including without limitation 
// the rights to use, copy, modify, merge, publish, distribute, sublicense, 
// and/or sell copies of the Software, and to permit persons to whom the 
// Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in 
// all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS 
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
// DEALINGS IN THE SOFTWARE.

namespace Duplicati.StreamUtil;

/// <summary>
/// Wraps a <see cref="Stream"/> and delegates all calls to it,
/// mapping the usual read/write calls to the async variants.
/// </summary>
public abstract class WrappingAsyncStream : WrappingStream
{
    /// <summary>
    /// Initializes a new instance of the <see cref="WrappingAsyncStream"/> class.
    /// </summary>
    /// <param name="stream">The stream to wrap.</param>
    public WrappingAsyncStream(Stream stream)
        : this(stream, true) { }

    /// <summary>
    /// Initializes a new instance of the <see cref="WrappingAsyncStream"/> class.
    /// </summary>
    /// <param name="stream">The stream to wrap.</param>
    /// <param name="disposeBaseStream">Whether to dispose the base stream when this stream is disposed.</param>
    public WrappingAsyncStream(Stream stream, bool disposeBaseStream)
        : base(stream, disposeBaseStream) { }

    /// <inheritdoc/>
    public override int Read(byte[] buffer, int offset, int count)
        => ReadImplAsync(buffer, offset, count, default).ConfigureAwait(false).GetAwaiter().GetResult();

    /// <inheritdoc/>
    public override void Write(byte[] buffer, int offset, int count)
        => WriteImplAsync(buffer, offset, count, default).ConfigureAwait(false).GetAwaiter().GetResult();

    /// <inheritdoc/>
    public override Task<int> ReadAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
        => ReadImplAsync(buffer, offset, count, cancellationToken);

    /// <inheritdoc/>
    public override Task WriteAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken)
        => WriteImplAsync(buffer, offset, count, cancellationToken);

    /// <summary>
    /// Reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read.
    /// </summary>
    /// <param name="buffer">An array of bytes. When this method returns, the buffer contains the specified byte array with the values between offset and (offset + count - 1) replaced by the bytes read from the current source.</param>
    /// <param name="offset">The zero-based byte offset in buffer at which to begin storing the data read from the current stream.</param>
    /// <param name="count">The maximum number of bytes to be read from the current stream.</param>
    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
    /// <returns>A task that represents the asynchronous read operation. The value of its <see cref="Task{TResult}.Result"/> property contains the total number of bytes read into the buffer. The result value can be less than the number of bytes requested if the number of bytes currently available is less than the requested number, or it can be 0 (zero) if the end of the stream has been reached.</returns>
    protected abstract Task<int> ReadImplAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken);

    /// <summary>
    /// Writes a sequence of bytes to the current stream and advances the current position within this stream by the number of bytes written.
    /// </summary>
    /// <param name="buffer">An array of bytes. This method copies count bytes from buffer to the current stream.</param>
    /// <param name="offset">The zero-based byte offset in buffer at which to begin copying bytes to the current stream.</param>
    /// <param name="count">The number of bytes to be written to the current stream.</param>
    /// <param name="cancellationToken">The token to monitor for cancellation requests.</param>
    /// <returns>A task that represents the asynchronous write operation.</returns>
    protected abstract Task WriteImplAsync(byte[] buffer, int offset, int count, CancellationToken cancellationToken);
}