[1/3] Proper path resolution: add openat functionality #2254
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This commit adds the `openat` functionality to `sys.FS`. On UNIX-like platforms, this is done with the `openat(2)` syscall. On Windows, this is done with [`NtCreateFile`][1]. This is the first in a series of commit that overhauls how paths are resolved. The wasi-filesystem spec now [describes][2] a path resolution implementation that uses `openat`. [1]: https://learn.microsoft.com/en-us/windows/win32/api/winternl/nf-winternl-ntcreatefile [2]: https://github.com/WebAssembly/wasi-filesystem/blob/main/path-resolution.md Signed-off-by: Yage Hu <me@huyage.dev>
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FYI I can't stack PRs on top of this one because I can't push branches to this repo. |
| @@ -71,7 +72,7 @@ func (r *ReadFS) Utimens(path string, atim, mtim int64) experimentalsys.Errno { | |||
| } | |||
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| // compile-time check to ensure readFile implements api.File. | |||
| var _ experimentalsys.File = (*readFile)(nil) | |||
| var _ fsapi.File = (*readFile)(nil) | |||
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this was intentionally implementing only the experimental public VFS API. In fact I think this experimental VFS should not expose OpenAt
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Thanks for the context! I had thought it was an oversight.
| OpenAt( | ||
| fs experimentalsys.FS, | ||
| path string, | ||
| flag experimentalsys.Oflag, | ||
| mode fs.FileMode, | ||
| ) (experimentalsys.File, experimentalsys.Errno) |
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do we really need to expose this at this level?
the reason I am asking is that this obviously only applies to hierarchical FSs, but it won't work (as you can see later) on other types of file descriptors such as sockets or stdin/err/out. Could it be possible to keep this internal and limited to tree-like file systems?
Essentially, the final goal of this (series of) PR is to introduce an API that will reproduce the correct behavior when resolving paths, so it would great if we can scope it only to files for which "paths" make sense.
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It definitely doesn't need to be exposed at this level. I misunderstood your last comment and thought you wanted the method moved from the public interface to a private one.
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well, that was a fair assumption, but I was wondering if we could keep it as an implementation detail of Open for those FSs that need hierarchical file access 🤔
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Quick update: I'm on a cross-country move at the moment. Will get around to this again after mid-August. Thanks for the speedy reviews @evacchi |
This PR is the first in a series that will implement the path resolution algorithm described by wasi-filesystem. Since this new path resolution implementation requires the use of
openat, this PR first introducesopenat(2)and its Windows equivalentNtCreateFileto Wazero.openat(2)openat(2)NtCreateFileinternal/sysfs/dirfs_test.goThe next PR will stack on this one and use the
openatfunctionality to implement path resolution.