feat(metadata): implement Windows xattrs via NTFS Alternate Data Streams (#1867)#3536
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…ams (#1867) Add a Windows backend for the cross-platform xattr layer that maps each named extended attribute onto an NTFS Alternate Data Stream using the `path:streamname:$DATA` syntax. The four POSIX primitives are now backed by `FindFirstStreamW`/`FindNextStreamW` for listing, `CreateFileW` + `ReadFile`/`WriteFile` for read and write, and `DeleteFileW` for removal. Stream-name parsing strips the `:` prefix and `:$DATA` suffix returned by NTFS so the wire-format names match the Unix xattr names exposed by the existing `xattr` crate backend. Refactor the per-attribute primitives in `crates/metadata/src/xattr.rs` to take raw `&[u8]` names and dispatch to a platform backend module (`xattr_unix` or `xattr_windows`). The Unix backend continues to wrap the `xattr` crate; the new Windows backend lives in a separate file under the same `feature = "xattr"` gate so the cross-platform layer remains backend-agnostic. The public API (`read_xattrs_for_wire`, `sync_xattrs`, `apply_xattrs_from_list`) is unchanged and the upstream rsync namespace-filtering policy still applies on Linux. Unsafe FFI is contained in `xattr_windows.rs` with `#![allow(unsafe_code)]` matching the existing convention for platform wrappers in the metadata crate (alongside `acl_windows`, `ownership`, `id_lookup`). Resource management uses RAII wrappers around `FindClose` and `CloseHandle` so handles are released on every error path. Tests cover the stream-name parser, input validation in `stream_path_wide`, and a write/read/list/remove round-trip that gracefully skips when the test volume does not support ADS (e.g. FAT32 runners). Refs #1867
The Windows ADS xattr backend used `windows::Win32::Storage::FileSystem::{
ReadFile, WriteFile}`, which are gated behind the `Win32_System_IO`
feature in `windows = "0.62"`. Cross-compiling to
`x86_64-pc-windows-gnu` therefore failed with `no `ReadFile` /
`WriteFile` in `Win32::Storage::FileSystem``. `FindFirstStreamW`'s
`dwflags` argument also takes `Option<u32>`, but the call site passed a
bare `0`.
Replace the raw `ReadFile`/`WriteFile` calls with `std::fs::File`
constructed from the Win32 `HANDLE` via `FromRawHandle`, so the read
and write paths use stdlib I/O instead of FFI bindings that depend on
an additional `windows` crate feature. The `File` takes ownership of
the handle and closes it on drop, replacing the now-unused
`OwnedHandle` wrapper. Wrap the reserved-must-be-zero `dwflags`
argument in `Some(0)` to match the binding signature.
No new Cargo features and no changes outside `crates/metadata/`.
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…ams (#1867) (#3536) * feat(metadata): implement Windows xattrs via NTFS Alternate Data Streams (#1867) Add a Windows backend for the cross-platform xattr layer that maps each named extended attribute onto an NTFS Alternate Data Stream using the `path:streamname:$DATA` syntax. The four POSIX primitives are now backed by `FindFirstStreamW`/`FindNextStreamW` for listing, `CreateFileW` + `ReadFile`/`WriteFile` for read and write, and `DeleteFileW` for removal. Stream-name parsing strips the `:` prefix and `:$DATA` suffix returned by NTFS so the wire-format names match the Unix xattr names exposed by the existing `xattr` crate backend. Refactor the per-attribute primitives in `crates/metadata/src/xattr.rs` to take raw `&[u8]` names and dispatch to a platform backend module (`xattr_unix` or `xattr_windows`). The Unix backend continues to wrap the `xattr` crate; the new Windows backend lives in a separate file under the same `feature = "xattr"` gate so the cross-platform layer remains backend-agnostic. The public API (`read_xattrs_for_wire`, `sync_xattrs`, `apply_xattrs_from_list`) is unchanged and the upstream rsync namespace-filtering policy still applies on Linux. Unsafe FFI is contained in `xattr_windows.rs` with `#![allow(unsafe_code)]` matching the existing convention for platform wrappers in the metadata crate (alongside `acl_windows`, `ownership`, `id_lookup`). Resource management uses RAII wrappers around `FindClose` and `CloseHandle` so handles are released on every error path. Tests cover the stream-name parser, input validation in `stream_path_wide`, and a write/read/list/remove round-trip that gracefully skips when the test volume does not support ADS (e.g. FAT32 runners). Refs #1867 * style(metadata): cargo fmt * fix(metadata): make ADS xattr impl cross-compile for windows-gnu The Windows ADS xattr backend used `windows::Win32::Storage::FileSystem::{ ReadFile, WriteFile}`, which are gated behind the `Win32_System_IO` feature in `windows = "0.62"`. Cross-compiling to `x86_64-pc-windows-gnu` therefore failed with `no `ReadFile` / `WriteFile` in `Win32::Storage::FileSystem``. `FindFirstStreamW`'s `dwflags` argument also takes `Option<u32>`, but the call site passed a bare `0`. Replace the raw `ReadFile`/`WriteFile` calls with `std::fs::File` constructed from the Win32 `HANDLE` via `FromRawHandle`, so the read and write paths use stdlib I/O instead of FFI bindings that depend on an additional `windows` crate feature. The `File` takes ownership of the handle and closes it on drop, replacing the now-unused `OwnedHandle` wrapper. Wrap the reserved-must-be-zero `dwflags` argument in `Some(0)` to match the binding signature. No new Cargo features and no changes outside `crates/metadata/`. * style(metadata): cargo fmt xattr_windows imports
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Summary
path:streamname:$DATAsyntax.FindFirstStreamW/FindNextStreamWfor listing,CreateFileW+ReadFile/WriteFilefor read/write, andDeleteFileWfor removal. Stream-name parsing strips the:prefix and:$DATAsuffix so wire-format names match the existing Unix xattr names.crates/metadata/src/xattr.rsto dispatch through a platform backend module (xattr_unixorxattr_windows) while keeping the public API (read_xattrs_for_wire,sync_xattrs,apply_xattrs_from_list) and Linux namespace policy unchanged.xattr_windows.rs(#![allow(unsafe_code)]) and uses RAII wrappers aroundFindCloseandCloseHandlefor handle cleanup. Matches the convention used byacl_windows,ownership, andid_lookupin the same crate.Refs #1867
Test plan
xattr_windows::tests, gracefully skips on FAT32)::$DATAskip, non-data-stream rejection)stream_path_wideinput validation (empty, embedded:, non-UTF-8)xattr.rscross-platform tests on Linux (existing tests still green viaxattr_unixbackend)