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[Tar] Fill in the file size even if the file is empty. #106409

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Merged
merged 4 commits into from
Aug 23, 2024
Merged

[Tar] Fill in the file size even if the file is empty. #106409

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6713bab
[Tar] Fill in the file size even if the file is empty.
sobczyk Aug 14, 2024
9f8b4c1
fix tests, set size only when datastream is not null
sobczyk Aug 15, 2024
94f3251
Add unit tests for size header of an empty file
sobczyk Aug 21, 2024
d3f301b
Scope disposables
sobczyk Aug 21, 2024
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2 changes: 1 addition & 1 deletion src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHeader.Write.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -629,7 +629,7 @@ private int WriteCommonFields(Span<byte> buffer, TarEntryType actualEntryType)
checksum += FormatNumeric(_gid, buffer.Slice(FieldLocations.Gid, FieldLengths.Gid));
}

if (_size > 0)
if (_dataStream != null && _size >= 0)
{
checksum += FormatNumeric(_size, buffer.Slice(FieldLocations.Size, FieldLengths.Size));
}
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16 changes: 16 additions & 0 deletions src/libraries/System.Formats.Tar/tests/TarWriter/TarWriter.Tests.cs
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Expand Up @@ -2,6 +2,7 @@
// The .NET Foundation licenses this file to you under the MIT license.

using System.IO;
using System.Linq;
using Xunit;

namespace System.Formats.Tar.Tests
Expand Down Expand Up @@ -350,5 +351,20 @@ private int GetChecksumForFormatSpecificFields(TarEntry entry, TarEntryFormat fo
// Gnu BlockDevice: 623 + 1004 + 686 + 1142 = 3455
return checksum;
}

[Fact]
void Verify_Size_RegularFile_Empty()
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@adamsitnik adamsitnik Aug 26, 2024

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nit: the test methods should be public

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@am11 am11 Sep 10, 2024

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Yup, for consistency and repo conventions. However, it is known to work with xunit: xunit/xunit#2438 (reply in thread) :)

{
MemoryStream emptyData = new(0);
MemoryStream output = new();
TarWriter archive = new(output, TarEntryFormat.Pax);
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@carlossanlop carlossanlop Aug 21, 2024

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Did you only see the problem in Pax, or is this the only format that you tested?

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@sobczyk sobczyk Aug 21, 2024

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The one I tested, but the problem would apply equally to all, since small sizes are encoded the same way.

PaxTarEntry te = new(TarEntryType.RegularFile, "zero_size")
{ DataStream = emptyData };
archive.WriteEntry(te);
var sizeBuffer = output.GetBuffer()[1148..(1148 + 12)];
// we expect ocal zeros
byte[] expected = [0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0];
Assert.True(sizeBuffer.SequenceEqual(expected));
}
}
}