293 lines
11 KiB
Go
293 lines
11 KiB
Go
package sys
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import (
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"io/fs"
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"github.com/tetratelabs/wazero/sys"
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)
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// FS is a writeable fs.FS bridge backed by syscall functions needed for ABI
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// including WASI.
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//
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// Implementations should embed UnimplementedFS for forward compatibility. Any
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// unsupported method or parameter should return ENO
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//
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// # Errors
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//
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// All methods that can return an error return a Errno, which is zero
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// on success.
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//
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// Restricting to Errno matches current WebAssembly host functions,
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// which are constrained to well-known error codes. For example, WASI maps syscall
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// errors to u32 numeric values.
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//
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// # Notes
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//
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// A writable filesystem abstraction is not yet implemented as of Go 1.20. See
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// https://github.com/golang/go/issues/45757
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type FS interface {
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// OpenFile opens a file. It should be closed via Close on File.
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - EINVAL: `path` or `flag` is invalid.
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// - EISDIR: the path was a directory, but flag included O_RDWR or
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// O_WRONLY
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// - ENOENT: `path` doesn't exist and `flag` doesn't contain O_CREAT.
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//
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// # Constraints on the returned file
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//
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// Implementations that can read flags should enforce them regardless of
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// the type returned. For example, while os.File implements io.Writer,
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// attempts to write to a directory or a file opened with O_RDONLY fail
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// with a EBADF.
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//
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// Some implementations choose whether to enforce read-only opens, namely
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// fs.FS. While fs.FS is supported (Adapt), wazero cannot runtime enforce
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// open flags. Instead, we encourage good behavior and test our built-in
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// implementations.
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//
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// # Notes
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//
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// - This is like os.OpenFile, except the path is relative to this file
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// system, and Errno is returned instead of os.PathError.
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// - Implications of permissions when O_CREAT are described in Chmod notes.
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// - This is like `open` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html
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OpenFile(path string, flag Oflag, perm fs.FileMode) (File, Errno)
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// Lstat gets file status without following symbolic links.
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - ENOENT: `path` doesn't exist.
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//
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// # Notes
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//
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// - This is like syscall.Lstat, except the `path` is relative to this
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// file system.
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// - This is like `lstat` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/lstat.html
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// - An fs.FileInfo backed implementation sets atim, mtim and ctim to the
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// same value.
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// - When the path is a symbolic link, the stat returned is for the link,
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// not the file it refers to.
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Lstat(path string) (sys.Stat_t, Errno)
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// Stat gets file status.
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - ENOENT: `path` doesn't exist.
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//
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// # Notes
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//
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// - This is like syscall.Stat, except the `path` is relative to this
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// file system.
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// - This is like `stat` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/stat.html
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// - An fs.FileInfo backed implementation sets atim, mtim and ctim to the
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// same value.
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// - When the path is a symbolic link, the stat returned is for the file
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// it refers to.
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Stat(path string) (sys.Stat_t, Errno)
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// Mkdir makes a directory.
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - EINVAL: `path` is invalid.
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// - EEXIST: `path` exists and is a directory.
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// - ENOTDIR: `path` exists and is a file.
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//
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// # Notes
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//
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// - This is like syscall.Mkdir, except the `path` is relative to this
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// file system.
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// - This is like `mkdir` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/mkdir.html
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// - Implications of permissions are described in Chmod notes.
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Mkdir(path string, perm fs.FileMode) Errno
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// Chmod changes the mode of the file.
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - EINVAL: `path` is invalid.
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// - ENOENT: `path` does not exist.
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//
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// # Notes
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//
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// - This is like syscall.Chmod, except the `path` is relative to this
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// file system.
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// - This is like `chmod` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/chmod.html
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// - Windows ignores the execute bit, and any permissions come back as
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// group and world. For example, chmod of 0400 reads back as 0444, and
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// 0700 0666. Also, permissions on directories aren't supported at all.
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Chmod(path string, perm fs.FileMode) Errno
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// Rename renames file or directory.
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - EINVAL: `from` or `to` is invalid.
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// - ENOENT: `from` or `to` don't exist.
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// - ENOTDIR: `from` is a directory and `to` exists as a file.
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// - EISDIR: `from` is a file and `to` exists as a directory.
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// - ENOTEMPTY: `both from` and `to` are existing directory, but
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// `to` is not empty.
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//
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// # Notes
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//
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// - This is like syscall.Rename, except the paths are relative to this
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// file system.
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// - This is like `rename` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/rename.html
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// - Windows doesn't let you overwrite an existing directory.
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Rename(from, to string) Errno
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// Rmdir removes a directory.
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - EINVAL: `path` is invalid.
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// - ENOENT: `path` doesn't exist.
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// - ENOTDIR: `path` exists, but isn't a directory.
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// - ENOTEMPTY: `path` exists, but isn't empty.
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//
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// # Notes
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//
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// - This is like syscall.Rmdir, except the `path` is relative to this
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// file system.
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// - This is like `rmdir` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/rmdir.html
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// - As of Go 1.19, Windows maps ENOTDIR to ENOENT.
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Rmdir(path string) Errno
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// Unlink removes a directory entry.
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - EINVAL: `path` is invalid.
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// - ENOENT: `path` doesn't exist.
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// - EISDIR: `path` exists, but is a directory.
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//
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// # Notes
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//
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// - This is like syscall.Unlink, except the `path` is relative to this
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// file system.
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// - This is like `unlink` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/unlink.html
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// - On Windows, syscall.Unlink doesn't delete symlink to directory unlike other platforms. Implementations might
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// want to combine syscall.RemoveDirectory with syscall.Unlink in order to delete such links on Windows.
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// See https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-removedirectorya
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Unlink(path string) Errno
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// Link creates a "hard" link from oldPath to newPath, in contrast to a
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// soft link (via Symlink).
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - EPERM: `oldPath` is invalid.
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// - ENOENT: `oldPath` doesn't exist.
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// - EISDIR: `newPath` exists, but is a directory.
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//
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// # Notes
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//
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// - This is like syscall.Link, except the `oldPath` is relative to this
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// file system.
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// - This is like `link` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/link.html
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Link(oldPath, newPath string) Errno
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// Symlink creates a "soft" link from oldPath to newPath, in contrast to a
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// hard link (via Link).
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - EPERM: `oldPath` or `newPath` is invalid.
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// - EEXIST: `newPath` exists.
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//
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// # Notes
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//
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// - This is like syscall.Symlink, except the `oldPath` is relative to
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// this file system.
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// - This is like `symlink` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/symlink.html
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// - Only `newPath` is relative to this file system and `oldPath` is kept
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// as-is. That is because the link is only resolved relative to the
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// directory when dereferencing it (e.g. ReadLink).
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// See https://github.com/bytecodealliance/cap-std/blob/v1.0.4/cap-std/src/fs/dir.rs#L404-L409
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// for how others implement this.
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// - Symlinks in Windows requires `SeCreateSymbolicLinkPrivilege`.
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// Otherwise, EPERM results.
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// See https://learn.microsoft.com/en-us/windows/security/threat-protection/security-policy-settings/create-symbolic-links
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Symlink(oldPath, linkName string) Errno
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// Readlink reads the contents of a symbolic link.
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - EINVAL: `path` is invalid.
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//
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// # Notes
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//
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// - This is like syscall.Readlink, except the path is relative to this
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// filesystem.
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// - This is like `readlink` in POSIX. See
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// https://pubs.opengroup.org/onlinepubs/9699919799/functions/readlink.html
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// - On Windows, the path separator is different from other platforms,
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// but to provide consistent results to Wasm, this normalizes to a "/"
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// separator.
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Readlink(path string) (string, Errno)
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// Utimens set file access and modification times on a path relative to
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// this file system, at nanosecond precision.
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//
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// # Parameters
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//
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// If the path is a symbolic link, the target of expanding that link is
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// updated.
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//
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// The `atim` and `mtim` parameters refer to access and modification time
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// stamps as defined in sys.Stat_t. To retain one or the other, substitute
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// it with the pseudo-timestamp UTIME_OMIT.
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//
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// # Errors
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//
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// A zero Errno is success. The below are expected otherwise:
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// - ENOSYS: the implementation does not support this function.
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// - EINVAL: `path` is invalid.
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// - EEXIST: `path` exists and is a directory.
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// - ENOTDIR: `path` exists and is a file.
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//
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// # Notes
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//
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// - This is like syscall.UtimesNano and `utimensat` with `AT_FDCWD` in
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// POSIX. See https://pubs.opengroup.org/onlinepubs/9699919799/functions/futimens.html
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Utimens(path string, atim, mtim int64) Errno
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}
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