Previously, fs.path handled a few of the Windows path types, but not all of them, and only a few of them correctly/consistently. This commit aims to make `std.fs.path` correct and consistent in handling all possible Win32 path types.
This commit also slightly nudges the codebase towards a separation of Win32 paths and NT paths, as NT paths are not actually distinguishable from Win32 paths from looking at their contents alone (i.e. `\Device\Foo` could be an NT path or a Win32 rooted path, no way to tell without external context). This commit formalizes `std.fs.path` being fully concerned with Win32 paths, and having no special detection/handling of NT paths.
Resources on Windows path types, and Win32 vs NT paths:
- https://googleprojectzero.blogspot.com/2016/02/the-definitive-guide-on-win32-to-nt.html
- https://chrisdenton.github.io/omnipath/Overview.html
- https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file
API additions/changes/deprecations
- `std.os.windows.getWin32PathType` was added (it is analogous to `RtlDetermineDosPathNameType_U`), while `std.os.windows.getNamespacePrefix` and `std.os.windows.getUnprefixedPathType` were deleted. `getWin32PathType` forms the basis on which the updated `std.fs.path` functions operate.
- `std.fs.path.parsePath`, `std.fs.path.parsePathPosix`, and `std.fs.path.parsePathWindows` were added, while `std.fs.path.windowsParsePath` was deprecated. The new `parsePath` functions provide the "root" and the "kind" of a path, which is platform-specific. The now-deprecated `windowsParsePath` did not handle all possible path types, while the new `parsePathWindows` does.
- `std.fs.path.diskDesignator` has been deprecated in favor of `std.fs.path.parsePath`, and same deal with `diskDesignatorWindows` -> `parsePathWindows`
- `relativeWindows` is now a compile error when *not* targeting Windows, while `relativePosix` is now a compile error when targeting Windows. This is because those functions read/use the CWD path which will behave improperly when used from a system with different path semantics (e.g. calling `relativePosix` from a Windows system with a CWD like `C:\foo\bar` will give you a bogus result since that'd be treated as a single relative component when using POSIX semantics). This also allows `relativeWindows` to use Windows-specific APIs for getting the CWD and environment variables to cut down on allocations.
- `componentIterator`/`ComponentIterator.init` have been made infallible. These functions used to be able to error on UNC paths with an empty server component, and on paths that were assumed to be NT paths, but now:
+ We follow the lead of `RtlDetermineDosPathNameType_U`/`RtlGetFullPathName_U` in how it treats a UNC path with an empty server name (e.g. `\\\share`) and allow it, even if it'll be invalid at the time of usage
+ Now that `std.fs.path` assumes paths are Win32 paths and not NT paths, we don't have to worry about NT paths
Behavior changes
- `std.fs.path` generally: any combinations of mixed path separators for UNC paths are universally supported, e.g. `\/server/share`, `/\server\share`, `/\server/\\//share` are all seen as equivalent UNC paths
- `resolveWindows` handles all path types more appropriately/consistently.
+ `//` and `//foo` used to be treated as a relative path, but are now seen as UNC paths
+ If a rooted/drive-relative path cannot be resolved against anything more definite, the result will remain a rooted/drive-relative path.
+ I've created [a script to generate the results of a huge number of permutations of different path types](https://gist.github.com/squeek502/9eba7f19cad0d0d970ccafbc30f463bf) (the result of running the script is also included for anyone that'd like to vet the behavior).
- `dirnameWindows` now treats the drive-relative root as the dirname of a drive-relative path with a component, e.g. `dirname("C:foo")` is now `C:`, whereas before it would return null. `dirnameWindows` also handles local device paths appropriately now.
- `basenameWindows` now handles all path types more appropriately. The most notable change here is `//a` being treated as a partial UNC path now and therefore `basename` will return `""` for it, whereas before it would return `"a"`
- `relativeWindows` will now do its best to resolve against the most appropriate CWD for each path, e.g. relative for `D:foo` will look at the CWD to check if the drive letter matches, and if not, look at the special environment variable `=D:` to get the shell-defined CWD for that drive, and if that doesn't exist, then it'll resolve against `D:\`.
Implementation details
- `resolveWindows` previously looped through the paths twice to build up the relevant info before doing the actual resolution. Now, `resolveWindows` iterates backwards once and keeps track of which paths are actually relevant using a bit set, which also allows it to break from the loop when it's no longer possible for earlier paths to matter.
- A standalone test was added to test parts of `relativeWindows` since the CWD resolution logic depends on CWD information from the PEB and environment variables
Edge cases worth noting
- A strange piece of trivia that I found out while working on this is that it's technically possible to have a drive letter that it outside the intended A-Z range, or even outside the ASCII range entirely. Since we deal with both WTF-8 and WTF-16 paths, `path[0]`/`path[1]`/`path[2]` will not always refer to the same bits of information, so to get consistent behavior, some decision about how to deal with this edge case had to be made. I've made the choice to conform with how `RtlDetermineDosPathNameType_U` works, i.e. treat the first WTF-16 code unit as the drive letter. This means that when working with WTF-8, checking for drive-relative/drive-absolute paths is a bit more complicated. For more details, see the lengthy comment in `std.os.windows.getWin32PathType`
- `relativeWindows` will now almost always be able to return either a fully-qualified absolute path or a relative path, but there's one scenario where it may return a rooted path: when the CWD gotten from the PEB is not a drive-absolute or UNC path (if that's actually feasible/possible?). An alternative approach to this scenario might be to resolve against the `HOMEDRIVE` env var if available, and/or default to `C:\` as a last resort in order to guarantee the result of `relative` is never a rooted path.
- Partial UNC paths (e.g. `\\server` instead of `\\server\share`) are a bit awkward to handle, generally. Not entirely sure how best to handle them, so there may need to be another pass in the future to iron out any issues that arise. As of now the behavior is:
+ For `relative`, any part of a UNC disk designator is treated as the "root" and therefore isn't applicable for relative paths, e.g. calling `relative` with `\\server` and `\\server\share` will result in `\\server\share` rather than just `share` and if `relative` is called with `\\server\foo` and `\\server\bar` the result will be `\\server\bar` rather than `..\bar`
+ For `resolve`, any part of a UNC disk designator is also treated as the "root", but relative and rooted paths are still elligable for filling in missing portions of the disk designator, e.g. `resolve` with `\\server` and `foo` or `\foo` will result in `\\server\foo`
Fixes#25703Closes#25702
Deprecated aliases that are now compile errors:
- `std.fs.MAX_PATH_BYTES` (renamed to `std.fs.max_path_bytes`)
- `std.mem.tokenize` (split into `tokenizeAny`, `tokenizeSequence`, `tokenizeScalar`)
- `std.mem.split` (split into `splitSequence`, `splitAny`, `splitScalar`)
- `std.mem.splitBackwards` (split into `splitBackwardsSequence`, `splitBackwardsAny`, `splitBackwardsScalar`)
- `std.unicode`
+ `utf16leToUtf8Alloc`, `utf16leToUtf8AllocZ`, `utf16leToUtf8`, `fmtUtf16le` (all renamed to have capitalized `Le`)
+ `utf8ToUtf16LeWithNull` (renamed to `utf8ToUtf16LeAllocZ`)
- `std.zig.CrossTarget` (moved to `std.Target.Query`)
Deprecated `lib/std/std.zig` decls were deleted instead of made a `@compileError` because the `refAllDecls` in the test block would trigger the `@compileError`. The deleted top-level `std` namespaces are:
- `std.rand` (renamed to `std.Random`)
- `std.TailQueue` (renamed to `std.DoublyLinkedList`)
- `std.ChildProcess` (renamed/moved to `std.process.Child`)
This is not exhaustive. Deprecated aliases that I didn't touch:
+ `std.io.*`
+ `std.Build.*`
+ `std.builtin.Mode`
+ `std.zig.c_translation.CIntLiteralRadix`
+ anything in `src/`
This implementation is now a direct replacement for the `kernel32` one.
New bitflags for named pipes and other generic ones were added based on
browsing the ReactOS sources.
`UNICODE_STRING.Buffer` has also been changed to be nullable, as
this is what makes the implementation work.
This required some changes to places accesssing the buffer after a
`SUCCESS`ful return, most notably `QueryObjectName` which even referred
to it being nullable.
Previously, a relative path like `..` would:
- Attempt to be normalized (i.e. remove . and .. without any path resolution), but would error with TooManyParentDirs
- This would make wToPrefixedFileW run it through `RtlGetFullPathName_U` to do the necessary path resolution, but `RtlGetFullPathName_U` always resolves relative paths relative to the CWD
Instead, when TooManyParentDirs occurs, we now look up the path of the passed in `dir` (if it's non-null) and append the relative path to it before giving it to `RtlGetFullPathName_U`. If `dir` is null, then we just give it RtlGetFullPathName_U directly and let it resolve it relative to the CWD.
Closes#16779
There are many different types of Windows paths, and there are a few different possible namespaces on top of that. Before this commit, NT namespaced paths were somewhat supported, and for Win32 paths (those without a namespace prefix), only relative and drive absolute paths were supported. After this commit, all of the following are supported:
- Device namespaced paths (`\\.\`)
- Verbatim paths (`\\?\`)
- NT-namespaced paths (`\??\`)
- Relative paths (`foo`)
- Drive-absolute paths (`C:\foo`)
- Drive-relative paths (`C:foo`)
- Rooted paths (`\foo`)
- UNC absolute paths (`\\server\share\foo`)
- Root local device paths (`\\.` or `\\?` exactly)
Plus:
- Any of the path types and namespace types can be mixed and matched together as appropriate.
- All of the `std.os.windows.*ToPrefixedFileW` functions will accept any path type, prefixed or not, and do the appropriate thing to convert them to an NT-prefixed path if necessary.
This is achieved by making the `std.os.windows.*ToPrefixedFileW` functions behave like `ntdll.RtlDosPathNameToNtPathName_U`, but with a few differences:
- Does not allocate on the heap (this is why we can't use `ntdll.RtlDosPathNameToNtPathName_U` directly, it does internal heap allocation).
- Relative paths are kept as relative unless they contain too many .. components, in which case they are treated as 'drive relative' and resolved against the CWD (this is how it behaved before this commit as well).
- Special case device names like COM1, NUL, etc are not handled specially (TODO)
- `.` and space are not stripped from the end of relative paths (potential TODO)
Most of the non-trivial conversion of non-relative paths is done via `ntdll.RtlGetFullPathName_U`, which AFAIK is used internally by `ntdll.RtlDosPathNameToNtPathName_U`.
Some relevant reading on Windows paths:
- https://googleprojectzero.blogspot.com/2016/02/the-definitive-guide-on-win32-to-nt.html
- https://chrisdenton.github.io/omnipath/Overview.htmlCloses#8205
Might close (untested) #12729
Note:
- This removes checking for illegal characters in `std.os.windows.sliceToPrefixedFileW`, since the previous solution (iterate the whole string and error if any illegal characters were found) was naive and won't work for all path types. This is further complicated by things like file streams (where `:` is used as a delimiter, e.g. `file.ext:stream_name:$DATA`) and things in the device namespace (where a path like `\\.\GLOBALROOT\??\UNC\localhost\C$\foo` is valid despite the `?`s in the path and is effectively equivalent to `C:\foo`). Truly validating paths is complicated and would need to be tailored to each path type. The illegal character checking being removed may open up users to more instances of hitting `OBJECT_NAME_INVALID => unreachable` when using `fs` APIs.
+ This is related to https://github.com/ziglang/zig/issues/15607
We already have a LICENSE file that covers the Zig Standard Library. We
no longer need to remind everyone that the license is MIT in every single
file.
Previously this was introduced to clarify the situation for a fork of
Zig that made Zig's LICENSE file harder to find, and replaced it with
their own license that required annual payments to their company.
However that fork now appears to be dead. So there is no need to
reinforce the copyright notice in every single file.
