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