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fix: parallel access to IFileStream #799

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Merged
merged 4 commits into from
Jul 13, 2025
Merged

fix: parallel access to IFileStream #799

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c27e6f4
fix: parallel access to `IFileStream`
vbreuss Jul 13, 2025
8956801
Fix review issues
vbreuss Jul 13, 2025
d759543
Fix failing tests
vbreuss Jul 13, 2025
9267997
Cleanup code
vbreuss Jul 13, 2025
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27 changes: 26 additions & 1 deletion Source/Testably.Abstractions.Testing/FileSystem/FileStreamMock.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -177,6 +177,8 @@ public override int WriteTimeout
private bool _isContentChanged;
private bool _isDisposed;
private readonly IStorageLocation _location;
private long _maxWrite;
private long _minWrite = long.MaxValue;
private readonly FileMode _mode;
private readonly FileOptions _options;
private readonly MemoryStream _stream;
Expand Down Expand Up @@ -248,7 +250,8 @@ private FileStreamMock(MemoryStream stream,

throw ExceptionFactory.FileAlreadyExists(
_fileSystem.Execute.Path.GetFullPath(base.Name), 17);
} else if (_mode.Equals(FileMode.CreateNew))
}
else if (_mode.Equals(FileMode.CreateNew))
{
throw ExceptionFactory.FileAlreadyExists(
_fileSystem.Execute.Path.GetFullPath(Name),
Expand Down Expand Up @@ -321,6 +324,8 @@ public override IAsyncResult BeginWrite(byte[] buffer,
throw ExceptionFactory.StreamDoesNotSupportWriting();
}

_minWrite = Position;
_maxWrite = Position + count;
return base.BeginWrite(buffer, offset, count, callback, state);
}

Expand Down Expand Up @@ -575,6 +580,8 @@ public override void Write(byte[] buffer, int offset, int count)
}

_isContentChanged = true;
_minWrite = Position;
_maxWrite = Position + count;
base.Write(buffer, offset, count);
}

Expand All @@ -592,6 +599,8 @@ public override void Write(ReadOnlySpan<byte> buffer)
}

_isContentChanged = true;
_minWrite = Position;
_maxWrite = Position + buffer.Length;
base.Write(buffer);
}
#endif
Expand All @@ -610,6 +619,8 @@ public override async Task WriteAsync(byte[] buffer, int offset, int count,
}

_isContentChanged = true;
_minWrite = Position;
_maxWrite = Position + count;
await base.WriteAsync(buffer, offset, count, cancellationToken);
}

Expand All @@ -628,6 +639,8 @@ public override async ValueTask WriteAsync(ReadOnlyMemory<byte> buffer,
}

_isContentChanged = true;
_minWrite = Position;
_maxWrite = Position + buffer.Length;
await base.WriteAsync(buffer, cancellationToken);
}
#endif
Expand All @@ -645,6 +658,8 @@ public override void WriteByte(byte value)
}

_isContentChanged = true;
_minWrite = Position;
_maxWrite = Position + 1L;
base.WriteByte(value);
}

Expand Down Expand Up @@ -679,6 +694,8 @@ private void InitializeStream()
else
{
_isContentChanged = true;
_minWrite = Position;
_maxWrite = Position;
}
}

Expand All @@ -696,12 +713,20 @@ private void InternalFlush()
_ = _stream.Read(data, 0, (int)Length);
_stream.Seek(position, SeekOrigin.Begin);
_container.WriteBytes(data);
_minWrite = long.MaxValue;
_maxWrite = 0;
}

private void OnBytesChanged(object? sender, EventArgs e)
{
byte[] existingContents = _container.GetBytes();
long position = _stream.Position;
if (_minWrite < _maxWrite)
{
_stream.Position = _minWrite;
_ = _stream.Read(existingContents, (int)_minWrite, (int)(_maxWrite - _minWrite));
}

_stream.Position = 0;
_stream.Write(existingContents, 0, existingContents.Length);
_stream.Position = position;
Expand Down
126 changes: 126 additions & 0 deletions Tests/Testably.Abstractions.Tests/FileSystem/FileStream/ParallelTests.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,126 @@
using System.IO;
using System.Text;

namespace Testably.Abstractions.Tests.FileSystem.FileStream;

[FileSystemTests]
public partial class ParallelTests
{
[Theory]
[AutoData]
public async Task MultipleFlush_DifferentLength_ShouldKeepAdditionalBytes(string path)
{
using (FileSystemStream stream1 = FileSystem.File.Open(path, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.ReadWrite))
{
using FileSystemStream stream2 = FileSystem.File.Open(path, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.ReadWrite);

stream2.Write(Encoding.UTF8.GetBytes("foo"), 0, 3);
stream1.Write(Encoding.UTF8.GetBytes("barfoo"), 0, 6);

await That(stream1).HasLength().EqualTo(6);
await That(stream2).HasLength().EqualTo(3);

stream1.Flush();

await That(stream1).HasLength().EqualTo(6);
await That(stream2).HasLength().EqualTo(6);

stream2.Flush();

await That(stream1).HasLength().EqualTo(6);
await That(stream2).HasLength().EqualTo(6);
}

await That(FileSystem.File.ReadAllText(path)).IsEqualTo("foofoo");
}

[Theory]
[AutoData]
public async Task MultipleFlush_DifferentPosition_ShouldKeepAdditionalBytes(string path)
{
FileSystem.File.WriteAllText(path, "AAAAAAAAAAAA");
using (FileSystemStream stream1 = FileSystem.File.Open(path, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.ReadWrite))
{
using FileSystemStream stream2 = FileSystem.File.Open(path, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.ReadWrite);
stream2.Position = 3;
stream1.Position = 2;

stream2.Write(Encoding.UTF8.GetBytes("CCC"), 0, 3);
stream1.Write(Encoding.UTF8.GetBytes("bbbbbb"), 0, 6);

stream1.Flush();
stream2.Flush();
}

await That(FileSystem.File.ReadAllText(path)).IsEqualTo("AAbCCCbbAAAA");
}

[Theory]
[AutoData]
public async Task MultipleFlush_DifferentPositionWithGaps_ShouldKeepAdditionalBytes(string path)
{
FileSystem.File.WriteAllText(path, "AAAAAAAAAAAA");
using (FileSystemStream stream1 = FileSystem.File.Open(path, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.ReadWrite))
{
using FileSystemStream stream2 = FileSystem.File.Open(path, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.ReadWrite);
stream1.Position = 2;

stream2.Position = 3;
stream2.Write(Encoding.UTF8.GetBytes("C"), 0, 1);
stream2.Position = 5;
stream2.Write(Encoding.UTF8.GetBytes("C"), 0, 1);
stream1.Write(Encoding.UTF8.GetBytes("bbbbbb"), 0, 6);

stream1.Flush();
stream2.Flush();
}

await That(FileSystem.File.ReadAllText(path)).IsEqualTo("AAbbbCbbAAAA");
}

[Theory]
[AutoData]
public async Task MultipleFlush_ShouldKeepLatestChanges(string path)
{
using (FileSystemStream stream1 = FileSystem.File.Open(path, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.ReadWrite))
{
using FileSystemStream stream2 = FileSystem.File.Open(path, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.ReadWrite);

stream2.Write(Encoding.UTF8.GetBytes("foo"), 0, 3);
stream1.Write(Encoding.UTF8.GetBytes("bar"), 0, 3);

stream1.Flush();
stream2.Flush();
}

await That(FileSystem.File.ReadAllText(path)).IsEqualTo("foo");
}

[Theory]
[AutoData]
public async Task WriteEmpty_ShouldNotOverwrite(string path)
{
using (FileSystemStream stream1 = FileSystem.File.Open(path, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.ReadWrite))
{
using FileSystemStream stream2 = FileSystem.File.Open(path, FileMode.OpenOrCreate,
FileAccess.Write, FileShare.ReadWrite);

stream2.Write(Encoding.UTF8.GetBytes(""), 0, 0);
stream1.Write(Encoding.UTF8.GetBytes("barfoo"), 0, 6);

stream1.Flush();
stream2.Flush();
}

await That(FileSystem.File.ReadAllText(path)).IsEqualTo("barfoo");
}
}
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