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File.stat: Support detection of Kind.sym_link on Windows

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Requires an extra NtQueryInformationFile call when FILE_ATTRIBUTE_REPARSE_POINT is set to determine if it's actually a symlink or some other kind of reparse point (https://learn.microsoft.com/en-us/windows/win32/fileio/reparse-point-tags). This is something that `File.Metadata.kind` was already doing, so the same technique is used in `stat`.

Also, replace the std.os.windows.DeviceIoControl call in `metadata` with NtQueryInformationFile (NtQueryInformationFile is what gets called during kernel32.GetFileInformationByHandleEx with FileAttributeTagInfo, verified using NtTrace).
This commit is contained in:
Ryan Liptak 2023-12-19 23:01:57 -08:00
parent f36ac227b1
commit 11a398af3e
3 changed files with 66 additions and 6 deletions
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38
lib/std/fs/File.zig
View File

@ -389,7 +389,26 @@ pub fn stat(self: File) StatError!Stat {
.inode = info.InternalInformation.IndexNumber,
.size = @as(u64, @bitCast(info.StandardInformation.EndOfFile)),
.mode = 0,
.kind = if (info.StandardInformation.Directory == 0) .file else .directory,
.kind = if (info.BasicInformation.FileAttributes & windows.FILE_ATTRIBUTE_REPARSE_POINT != 0) reparse_point: {
var tag_info: windows.FILE_ATTRIBUTE_TAG_INFO = undefined;
const tag_rc = windows.ntdll.NtQueryInformationFile(self.handle, &io_status_block, &tag_info, @sizeOf(windows.FILE_ATTRIBUTE_TAG_INFO), .FileAttributeTagInformation);
switch (tag_rc) {
.SUCCESS => {},
// INFO_LENGTH_MISMATCH and ACCESS_DENIED are the only documented possible errors
// https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-fscc/d295752f-ce89-4b98-8553-266d37c84f0e
.INFO_LENGTH_MISMATCH => unreachable,
.ACCESS_DENIED => return error.AccessDenied,
else => return windows.unexpectedStatus(rc),
}
if (tag_info.ReparseTag & windows.reparse_tag_name_surrogate_bit != 0) {
break :reparse_point .sym_link;
}
// Unknown reparse point
break :reparse_point .unknown;
} else if (info.BasicInformation.FileAttributes & windows.FILE_ATTRIBUTE_DIRECTORY != 0)
.directory
else
.file,
.atime = windows.fromSysTime(info.BasicInformation.LastAccessTime),
.mtime = windows.fromSysTime(info.BasicInformation.LastWriteTime),
.ctime = windows.fromSysTime(info.BasicInformation.CreationTime),
@ -791,7 +810,7 @@ pub const MetadataWindows = struct {
/// Can only return: `.file`, `.directory`, `.sym_link` or `.unknown`
pub fn kind(self: Self) Kind {
if (self.attributes & windows.FILE_ATTRIBUTE_REPARSE_POINT != 0) {
if (self.reparse_tag & 0x20000000 != 0) {
if (self.reparse_tag & windows.reparse_tag_name_surrogate_bit != 0) {
return .sym_link;
}
} else if (self.attributes & windows.FILE_ATTRIBUTE_DIRECTORY != 0) {
@ -842,10 +861,17 @@ pub fn metadata(self: File) MetadataError!Metadata {
const reparse_tag: windows.DWORD = reparse_blk: {
if (info.BasicInformation.FileAttributes & windows.FILE_ATTRIBUTE_REPARSE_POINT != 0) {
var reparse_buf: [windows.MAXIMUM_REPARSE_DATA_BUFFER_SIZE]u8 = undefined;
try windows.DeviceIoControl(self.handle, windows.FSCTL_GET_REPARSE_POINT, null, reparse_buf[0..]);
const reparse_struct: *const windows.REPARSE_DATA_BUFFER = @ptrCast(@alignCast(&reparse_buf[0]));
break :reparse_blk reparse_struct.ReparseTag;
var tag_info: windows.FILE_ATTRIBUTE_TAG_INFO = undefined;
const tag_rc = windows.ntdll.NtQueryInformationFile(self.handle, &io_status_block, &tag_info, @sizeOf(windows.FILE_ATTRIBUTE_TAG_INFO), .FileAttributeTagInformation);
switch (tag_rc) {
.SUCCESS => {},
// INFO_LENGTH_MISMATCH and ACCESS_DENIED are the only documented possible errors
// https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-fscc/d295752f-ce89-4b98-8553-266d37c84f0e
.INFO_LENGTH_MISMATCH => unreachable,
.ACCESS_DENIED => return error.AccessDenied,
else => return windows.unexpectedStatus(rc),
}
break :reparse_blk tag_info.ReparseTag;
}
break :reparse_blk 0;
};

25
lib/std/fs/test.zig
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@ -156,6 +156,31 @@ fn testReadLink(dir: Dir, target_path: []const u8, symlink_path: []const u8) !vo
try testing.expectEqualStrings(target_path, given);
}
test "stat on a symlink returns Kind.sym_link" {
try testWithAllSupportedPathTypes(struct {
fn impl(ctx: *TestContext) !void {
const dir_target_path = try ctx.transformPath("subdir");
try ctx.dir.makeDir(dir_target_path);
// TODO: Also test a symlink to a file.
// There's currently no way to avoid following symlinks when opening files.
// https://github.com/ziglang/zig/issues/18327
ctx.dir.symLink(dir_target_path, "symlink", .{ .is_directory = true }) catch |err| switch (err) {
// Symlink requires admin privileges on windows, so this test can legitimately fail.
error.AccessDenied => return error.SkipZigTest,
else => return err,
};
var symlink = try ctx.dir.openDir("symlink", .{ .no_follow = true });
defer symlink.close();
const stat = try symlink.stat();
try testing.expectEqual(File.Kind.sym_link, stat.kind);
}
}.impl);
}
test "relative symlink to parent directory" {
var tmp = tmpDir(.{});
defer tmp.cleanup();

9
lib/std/os/windows.zig
View File

@ -2972,6 +2972,15 @@ pub const FILE_INFORMATION_CLASS = enum(c_int) {
FileMaximumInformation,
};
pub const FILE_ATTRIBUTE_TAG_INFO = extern struct {
FileAttributes: DWORD,
ReparseTag: DWORD,
};
/// "If this bit is set, the file or directory represents another named entity in the system."
/// https://learn.microsoft.com/en-us/windows/win32/fileio/reparse-point-tags
pub const reparse_tag_name_surrogate_bit = 0x20000000;
pub const FILE_DISPOSITION_INFORMATION = extern struct {
DeleteFile: BOOLEAN,
};