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os: add Root
Add os.Root, a type which represents a directory and permits performing file operations within that directory. For #67002 Change-Id: I863f4f1bc320a89b1125ae4237761f3e9320a901 Reviewed-on: https://go-review.googlesource.com/c/go/+/612136 Reviewed-by: Ian Lance Taylor <[email protected]> Reviewed-by: Quim Muntal <[email protected]> LUCI-TryBot-Result: Go LUCI <[email protected]>
1 parent 558f537 commit 43d90c6

17 files changed

Lines changed: 2243 additions & 70 deletions

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‎api/next/67002.txt‎

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pkg os, func OpenRoot(string) (*Root, error) #67002
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pkg os, method (*Root) Close() error #67002
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pkg os, method (*Root) Create(string) (*File, error) #67002
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pkg os, method (*Root) Mkdir(string, fs.FileMode) error #67002
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pkg os, method (*Root) Name() string #67002
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pkg os, method (*Root) Open(string) (*File, error) #67002
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pkg os, method (*Root) OpenFile(string, int, fs.FileMode) (*File, error) #67002
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pkg os, method (*Root) OpenRoot(string) (*Root, error) #67002
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pkg os, type Root struct #67002

‎doc/next/6-stdlib/1-os-root.md‎

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### Directory-limited filesystem access
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<!-- go.dev/issue/67002 -->
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The new [os.Root] type provides the ability to perform filesystem
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operations within a specific directory.
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The [os.OpenRoot] function opens a directory and returns an [os.Root].
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Methods on [os.Root] operate within the directory and do not permit
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paths that refer to locations outside the directory, including
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ones that follow symbolic links out of the directory.
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- [os.Root.Open] opens a file for reading.
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- [os.Root.Create] creates a file.
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- [os.Root.OpenFile] is the generalized open call.
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- [os.Root.Mkdir] creates a directory.
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‎doc/next/6-stdlib/99-minor/os/67002.md‎

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<!-- os.Root -->

‎src/internal/syscall/windows/at_windows.go‎

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@@ -42,7 +42,7 @@ func Openat(dirfd syscall.Handle, name string, flag int, perm uint32) (_ syscall
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}
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if flag&syscall.O_APPEND != 0 {
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access |= FILE_APPEND_DATA
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// Remove GENERIC_WRITE access unless O_TRUNC is set,
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// Remove FILE_WRITE_DATA access unless O_TRUNC is set,
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// in which case we need it to truncate the file.
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if flag&syscall.O_TRUNC == 0 {
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access &^= FILE_WRITE_DATA
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fileAttrs,
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FILE_SHARE_READ|FILE_SHARE_WRITE|FILE_SHARE_DELETE,
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disposition,
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FILE_SYNCHRONOUS_IO_NONALERT|options,
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FILE_SYNCHRONOUS_IO_NONALERT|FILE_OPEN_FOR_BACKUP_INTENT|options,
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0,
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0,
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)

‎src/os/file.go‎

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@@ -398,6 +398,8 @@ func OpenFile(name string, flag int, perm FileMode) (*File, error) {
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return f, nil
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}
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var errPathEscapes = errors.New("path escapes from parent")
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// openDir opens a file which is assumed to be a directory. As such, it skips
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// the syscalls that make the file descriptor non-blocking as these take time
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// and will fail on file descriptors for directories.

‎src/os/file_windows.go‎

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@@ -415,10 +415,13 @@ func readReparseLink(path string) (string, error) {
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return "", err
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}
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defer syscall.CloseHandle(h)
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return readReparseLinkHandle(h)
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}
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func readReparseLinkHandle(h syscall.Handle) (string, error) {
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rdbbuf := make([]byte, syscall.MAXIMUM_REPARSE_DATA_BUFFER_SIZE)
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var bytesReturned uint32
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err = syscall.DeviceIoControl(h, syscall.FSCTL_GET_REPARSE_POINT, nil, 0, &rdbbuf[0], uint32(len(rdbbuf)), &bytesReturned, nil)
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err := syscall.DeviceIoControl(h, syscall.FSCTL_GET_REPARSE_POINT, nil, 0, &rdbbuf[0], uint32(len(rdbbuf)), &bytesReturned, nil)
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if err != nil {
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return "", err
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}

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