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Add the ArchiveComment property for ZipArchive class #1547
Description
Edit by carlossanlop: API Proposal here
When we make a zip package, the comment is very important function that we use it very often. The corefx has already implemented it, see the definition _archiveComment field at ZipArchive.cs#L32, the reader at ZipArchive.cs#L561 and the writter at ZipArchive.cs#L693.
We can inbreak the ZipArchive instance by reflect and modify the _archiveComment field, then saved zip file is fine.
Proposed API
Just make private field _archiveComment as public property ArchiveComment, or other advises.
Activity
ianhays commentedon Jan 30, 2017
related to https://github.com/dotnet/corefx/issues/14853 and (to a lesser extent) https://github.com/dotnet/corefx/issues/12066 and https://github.com/dotnet/corefx/issues/10223
There are many fields in the ZipArchive header that I would like to see exposed in some manner eventually. I'm a bit hesitant to start exposing them one-by-one as we may end up with a messy API that we wish we could change but can't because of compat. I'd rather we look at the entire Zip header and decide what to expose - and how - all at once. https://github.com/dotnet/corefx/issues/14853 is one possible way of doing this.
carlossanlop commentedon Sep 13, 2019
Python exposes the zip archive comment in their public APIs, for both the ZipFile (the actual archive) and the ZipInfo (an individual archive member).
Java offers only a get method for the ZipFile comment, but has a get and set methods for the ZipEntry.
WinZip and WinRAR have the ability to show it too. The
unziptool in Unix automatically prints the zip archive comment right before starting to extract files.7-zip, Windows Explorer and corefx do not show the zip archive comment, although Windows Explorer allows hovering on a zip file and show a snippet of that comment, but not all.
carlossanlop commentedon Sep 21, 2021
We are already collecting the archive comment:
runtime/src/libraries/System.IO.Compression/src/System/IO/Compression/ZipArchive.cs
Line 30 in 57bfe47
And the file comment:
runtime/src/libraries/System.IO.Compression/src/System/IO/Compression/ZipArchiveEntry.cs
Line 43 in 57bfe47
So making these fields public is just a matter of ensuring the setters are properly delimited according to the spec.
The API proposal may look like this:
namespace System.IO.Compression { public partial class ZipArchive : IDisposable { public ZipArchive(Stream stream); public ZipArchive(Stream stream, ZipArchiveMode mode); public ZipArchive(Stream stream, ZipArchiveMode mode, bool leaveOpen); public ZipArchive(Stream stream, ZipArchiveMode mode, bool leaveOpen, Encoding? entryNameEncoding); + public string? Comment { get; set; } public ReadOnlyCollection<ZipArchiveEntry> Entries { get; } public ZipArchiveMode Mode { get; } public ZipArchiveEntry CreateEntry(string entryName); public ZipArchiveEntry CreateEntry(string entryName, CompressionLevel compressionLevel); public void Dispose(); protected virtual void Dispose(bool disposing); public ZipArchiveEntry? GetEntry(string entryName); } public partial class ZipArchiveEntry { internal ZipArchiveEntry() { } public ZipArchive Archive { get ; } + public string? Comment { get; set; } public long CompressedLength { get ; } public uint Crc32 { get; } public int ExternalAttributes { get; set; } public string FullName { get; } public DateTimeOffset LastWriteTime { get; set; } public long Length { get; } public string Name { get; } public void Delete(); public Stream Open(); public override string ToString(); } }Questions
ZipArchive, should we also add a constructor that takes a comment? The question does not apply forZipArchiveEntrybecause it only has an internal default constructor.Commentdefault value be astring?or astring?Additional details
The ZIP file format spec indicates that:
Archive comment restrictions
Archive comment spec definition
Comment encoding
And also:
Max size of comment
File comment restrictions
File comment spec definition
Non-encryption of archive comment
Max size of comment
Note
There's mention of a
Info-ZIP Unicode Comment Extra Fieldin theThird party mappingssection of the spec. This is not related to the standard comments mentioned above.bartonjs commentedon Sep 21, 2021
Video
Since the spec says that there's always a comment (but it can be zero length) we don't think the properties should be nullable (null-returning). The setters can certainly accept null to normalize to whatever the default we have historically done. (string.Empty / "Built with .NET", whatever it is we do...)
If you don't want to do null-normalization, then remove the
[AllowNull]s, but it's probably nice to do.namespace System.IO.Compression { public partial class ZipArchive : IDisposable { public ZipArchive(Stream stream); public ZipArchive(Stream stream, ZipArchiveMode mode); public ZipArchive(Stream stream, ZipArchiveMode mode, bool leaveOpen); public ZipArchive(Stream stream, ZipArchiveMode mode, bool leaveOpen, Encoding? entryNameEncoding); + [AllowNull] + public string Comment { get; set; } public ReadOnlyCollection<ZipArchiveEntry> Entries { get; } public ZipArchiveMode Mode { get; } public ZipArchiveEntry CreateEntry(string entryName); public ZipArchiveEntry CreateEntry(string entryName, CompressionLevel compressionLevel); public void Dispose(); protected virtual void Dispose(bool disposing); public ZipArchiveEntry? GetEntry(string entryName); } public partial class ZipArchiveEntry { internal ZipArchiveEntry() { } public ZipArchive Archive { get ; } + [AllowNull] + public string Comment { get; set; } public long CompressedLength { get ; } public uint Crc32 { get; } public int ExternalAttributes { get; set; } public string FullName { get; } public DateTimeOffset LastWriteTime { get; set; } public long Length { get; } public string Name { get; } public void Delete(); public Stream Open(); public override string ToString(); } }