Cygwin 3.7 wishlist: read/write NTFS alternate data streams via openat(O_XATTR)

[Thomas Wolff]

Am 24.03.2025 um 17:08 schrieb Jeffrey Altman:
> On 3/24/2025 10:25 AM, Martin Wege via Cygwin wrote:
>> Hello,
>>
>> another wishlist entry (old one):
>> read/write NTFS alternate data streams via openat(O_XATTR)
>
> From my perspective as a filesystem developer, Extended Attributes and
> Alternate Data Streams are different concepts which I believe are
> inappropriate to mix.
>
> Filesystems can implement one, the other, both or neither.
>
> An Extended Attribute is a name:value pair that can be attached to an
> inode. The size of individual values and the sum of the value sizes
> are often quite constrained because they are stored in the inode
> metadata. Copying an inode is guaranteed to copy the Extended Attributes.
>
> Alternate Data Streams are typically represented as independent
> inodes. The Alternate Data Stream namespace can be represented by a
> directory inode referenced from the file inode. Each ADS inode might
> have their own Extended Attributes to go along with the data stream.
> ACLs on ADS inodes can also be independent of the ACL on the primary
> inode depending upon the implementation.
>
> Therefore, I am reluctant to see openat(O_XATTR) be used to access
> alternate data streams.
>
> Jeffrey Altman
Why not use the Windows syntax?
cat file.txt:ads.txt
etc. (Was this discussed before?)
Thomas