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Tweak internal IProgress usage for APM and sync UploadFile/DownloadFile #1805

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Rob-Hague wants to merge 1 commit into from
+62 −23
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Tweak internal IProgress usage for APM and sync UploadFile/DownloadFile #1805

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85 changes: 62 additions & 23 deletions src/Renci.SshNet/SftpClient.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -905,7 +905,7 @@ public void DownloadFile(string path, Stream output, Action<ulong>? downloadCall

if (downloadCallback != null)
{
downloadProgress = new Progress<DownloadFileProgressReport>(r => downloadCallback(r.TotalBytesDownloaded));
downloadProgress = new SynchronousProgress<DownloadFileProgressReport>(r => downloadCallback(r.TotalBytesDownloaded));
}

InternalDownloadFile(
Expand Down Expand Up @@ -934,7 +934,7 @@ public Task DownloadFileAsync(string path, Stream output, IProgress<DownloadFile
path,
output,
asyncResult: null,
downloadProgress: downloadProgress,
downloadProgress,
isAsync: true,
cancellationToken);
}
Expand Down Expand Up @@ -1011,7 +1011,11 @@ public IAsyncResult BeginDownloadFile(string path, Stream output, AsyncCallback?

if (downloadCallback != null)
{
downloadProgress = new Progress<DownloadFileProgressReport>(r => downloadCallback(r.TotalBytesDownloaded));
// The System.Progress<T> ctor captures the current synchronization context
// and posts the progress reports to it. For back-compat with previous
// versions which always posted the callback to the threadpool regardless of
// sync context, we use a custom IProgress<T> impl.
downloadProgress = new ThreadPoolProgress<DownloadFileProgressReport>(r => downloadCallback(r.TotalBytesDownloaded));
}

var asyncResult = new SftpDownloadAsyncResult(asyncCallback, state);
Expand Down Expand Up @@ -1089,7 +1093,7 @@ public void UploadFile(Stream input, string path, bool canOverride, Action<ulong

if (uploadCallback != null)
{
uploadProgress = new Progress<UploadFileProgressReport>(r => uploadCallback(r.TotalBytesUploaded));
uploadProgress = new SynchronousProgress<UploadFileProgressReport>(r => uploadCallback(r.TotalBytesUploaded));
}
Comment on lines 1094 to 1097

@Rob-Hague Rob-Hague Jun 20, 2026

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fair point


InternalUploadFile(
Expand Down Expand Up @@ -1273,7 +1277,11 @@ public IAsyncResult BeginUploadFile(Stream input, string path, bool canOverride,

if (uploadCallback != null)
{
uploadProgress = new Progress<UploadFileProgressReport>(r => uploadCallback(r.TotalBytesUploaded));
// The System.Progress<T> ctor captures the current synchronization context
// and posts the progress reports to it. For back-compat with previous
// versions which always posted the callback to the threadpool regardless of
// sync context, we use a custom IProgress<T> impl.
uploadProgress = new ThreadPoolProgress<UploadFileProgressReport>(r => uploadCallback(r.TotalBytesUploaded));
}

var asyncResult = new SftpUploadAsyncResult(asyncCallback, state);
Expand Down Expand Up @@ -2417,16 +2425,10 @@ private async Task InternalDownloadFile(

asyncResult?.Update(totalBytesRead);

if (downloadProgress is not null)
downloadProgress?.Report(new DownloadFileProgressReport()
{
// Copy offset to ensure it's not modified between now and execution of callback
var report = new DownloadFileProgressReport()
{
TotalBytesDownloaded = totalBytesRead,
};

downloadProgress.Report(report);
}
TotalBytesDownloaded = totalBytesRead
});
}
}
finally
Expand Down Expand Up @@ -2536,16 +2538,10 @@ private async Task InternalUploadFile(

asyncResult?.Update(writtenBytes);

// Call callback to report number of bytes written
if (uploadProgress is not null)
uploadProgress?.Report(new UploadFileProgressReport()
{
UploadFileProgressReport report = new()
{
TotalBytesUploaded = writtenBytes,
};

uploadProgress.Report(report);
}
TotalBytesUploaded = writtenBytes
});
}
finally
{
Expand Down Expand Up @@ -2652,5 +2648,48 @@ private ISftpSession CreateAndConnectToSftpSession()
throw;
}
}

/// <summary>
/// An <see cref="IProgress{T}"/> implementation that posts callbacks to the threadpool.
/// </summary>
private sealed class ThreadPoolProgress<T> : IProgress<T>
{
private readonly Action<T> _handler;

public ThreadPoolProgress(Action<T> handler)
{
Debug.Assert(handler != null);
_handler = handler!;
}

void IProgress<T>.Report(T value)
{
_ = ThreadPool.QueueUserWorkItem(static state =>
{
var (handler, value) = ((Action<T>, T))state!;
handler(value);
},
(_handler, value));
}
}

/// <summary>
/// An <see cref="IProgress{T}"/> implementation that invokes callbacks synchronously.
/// </summary>
private sealed class SynchronousProgress<T> : IProgress<T>
{
private readonly Action<T> _handler;

public SynchronousProgress(Action<T> handler)
{
Debug.Assert(handler != null);
_handler = handler!;
}

void IProgress<T>.Report(T value)
{
_handler.Invoke(value);
}
Comment on lines +2652 to +2692
}
}
}