LambdaInterceptStream.cs

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namespace Duplicati.StreamUtil;

/// <summary>
/// Class that wraps a stream and allows for intercepting read and write operations.
/// Intended for use in testing.
/// </summary>
public class LambdaInterceptStream : WrappingStream
{
    /// <summary>
    /// Initializes a new instance of the <see cref="LambdaInterceptStream"/> class.
    /// </summary>
    /// <param name="baseStream">The stream to wrap.</param>
    public LambdaInterceptStream(Stream baseStream) : base(baseStream) { }

    /// <summary>
    /// The action to perform before a read operation.
    /// </summary>
    public Action<byte[], int, int>? PreReadTask { get; set; }
    /// <summary>
    /// The action to perform after a read operation.
    /// </summary>
    public Action<byte[], int, int, int>? PostReadTask { get; set; }
    /// <summary>
    /// The action to perform before a write operation.
    /// </summary>
    public Action<byte[], int, int>? PreWriteTask { get; set; }
    /// <summary>
    /// The action to perform after a write operation.
    /// </summary>
    public Action<byte[], int, int, int>? PostWriteTask { get; set; }

    /// <inheritdoc/>
    public override int Read(byte[] buffer, int offset, int count)
    {
        PreReadTask?.Invoke(buffer, offset, count);
        var read = BaseStream.Read(buffer, offset, count);
        PostReadTask?.Invoke(buffer, offset, count, read);
        return read;
    }

    /// <inheritdoc/>
    public override void Write(byte[] buffer, int offset, int count)
    {
        PreWriteTask?.Invoke(buffer, offset, count);
        BaseStream.Write(buffer, offset, count);
        PostWriteTask?.Invoke(buffer, offset, count, count);
    }
}