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//! Types for interacting with Theseus standard I/O and file system via POSIX-style abstraction.
//!
//! This module provides APIs to:
//! * interact with a file descriptor table (open path, close fd, get underlying Theseus handle).
//! * read, write, or seek a file system node or standard I/O
//!
//! This abstraction is necessary as WASI assumes a POSIX-style file descriptor table interface.
//!
use alloc::string::String;
use core::{cmp, convert::TryFrom as _};
use fs_node::{DirRef, FileOrDir, FileRef, FsNode};
use hashbrown::HashMap;
use memfs::MemFile;
use path::{PathBuf, Path};
const FIRST_NONRESERVED_FD: wasi::Fd = 3;
/// File types that can be accessed through file descriptor table.
pub enum PosixNodeOrStdio {
/// Standard input.
Stdin,
/// Standard output.
Stdout,
/// Standard error.
Stderr,
/// An underlying file system node.
Inode(PosixNode),
}
impl PosixNodeOrStdio {
/// Writes data from the given `buffer` to this file.
///
/// The number of bytes written is dictated by the length of the given `buffer`.
///
/// # Arguments
/// * `buffer`: the buffer from which data will be written.
///
/// # Return
/// If successful, returns the number of bytes written to this file.
/// Otherwise, returns a wasi::Errno.
pub fn write(&mut self, buffer: &[u8]) -> Result<usize, wasi::Errno> {
match self {
PosixNodeOrStdio::Stdin => Err(wasi::ERRNO_NOTSUP),
PosixNodeOrStdio::Stdout => match app_io::stdout().unwrap().write_all(buffer) {
Ok(_) => Ok(buffer.len()),
Err(_) => Err(wasi::ERRNO_IO),
},
PosixNodeOrStdio::Stderr => match app_io::stderr().unwrap().write_all(buffer) {
Ok(_) => Ok(buffer.len()),
Err(_) => Err(wasi::ERRNO_IO),
},
PosixNodeOrStdio::Inode(posix_node) => posix_node.write(buffer),
}
}
/// Reads data from this file into the given `buffer`.
///
/// The number of bytes read is dictated by the length of the given `buffer`.
///
/// # Arguments
/// * `buffer`: the buffer into which the data will be read.
///
/// # Return
/// If successful, returns the number of bytes read into this file.
/// Otherwise, returns a wasi::Errno.
pub fn read(&mut self, buffer: &mut [u8]) -> Result<usize, wasi::Errno> {
match self {
PosixNodeOrStdio::Stdin => match app_io::stdin().unwrap().read(buffer) {
Ok(bytes_read) => Ok(bytes_read),
Err(_) => Err(wasi::ERRNO_IO),
},
PosixNodeOrStdio::Stdout => Err(wasi::ERRNO_NOTSUP),
PosixNodeOrStdio::Stderr => Err(wasi::ERRNO_NOTSUP),
PosixNodeOrStdio::Inode(posix_node) => posix_node.read(buffer),
}
}
/// Move the offset of this file.
///
/// # Arguments
/// * `offset`: the number of bytes to move.
/// * `whence`: the base from which the offset is relative.
///
/// # Return
/// If successful, returns the resulting offset of this file.
/// Otherwise, returns a wasi::Errno.
pub fn seek(
&mut self,
offset: wasi::Filedelta,
whence: wasi::Whence,
) -> Result<usize, wasi::Errno> {
match self {
PosixNodeOrStdio::Stdin => Err(wasi::ERRNO_NOTSUP),
PosixNodeOrStdio::Stdout => Err(wasi::ERRNO_NOTSUP),
PosixNodeOrStdio::Stderr => Err(wasi::ERRNO_NOTSUP),
PosixNodeOrStdio::Inode(posix_node) => posix_node.seek(offset, whence),
}
}
}
/// A wrapper around Theseus FileOrDir to provide WASI-expected POSIX features.
pub struct PosixNode {
/// Underlying Theseus FileOrDir.
pub theseus_file_or_dir: FileOrDir,
/// File system ights that apply to this file descriptor.
fs_rights_base: wasi::Rights,
/// Maximum set of rights applied to file descriptors opened through this file descriptor.
fs_rights_inheriting: wasi::Rights,
/// File descriptor flags.
/// NOTE: contains unused flags for synchornized I/O, non-blocking mode.
fs_flags: wasi::Fdflags,
/// Offset of this file descriptor.
offset: usize,
}
impl PosixNode {
/// Instantiates a new PosixNode.
///
/// # Arguments
/// * `file_or_dir`: underlying Theseus FileOrDir.
/// * `fs_rights`: rights applying to this file descriptor.
/// * `fs_rights_inheriting`: rights applying to inherting file descriptors.
/// * `fs_flags`: file descriptor flags.
///
/// # Return
/// Returns a PosixNode of a FileOrDir with specified permissions.
pub fn new(
file_or_dir: FileOrDir,
fs_rights_base: wasi::Rights,
fs_rights_inheriting: wasi::Rights,
fs_flags: wasi::Fdflags,
) -> PosixNode {
PosixNode {
theseus_file_or_dir: file_or_dir,
fs_rights_base,
fs_rights_inheriting,
fs_flags,
offset: 0,
}
}
/// Get path relative to working directory of this file descriptor.
///
/// # Return
/// Returns relative path of file descriptor as a string.
pub fn get_relative_path(&self) -> String {
let absolute_path = PathBuf::from(self.theseus_file_or_dir.get_absolute_path());
let wd_path = task::with_current_task(|t|
PathBuf::from(t.get_env().lock().cwd())
).expect("couldn't get current task");
let relative_path = absolute_path.relative(wd_path).unwrap();
String::from(relative_path)
}
/// Get file system rights of this file descriptor.
///
/// # Return
/// Returns file system rights of this file descriptor.
pub fn fs_rights_base(&self) -> wasi::Rights {
self.fs_rights_base
}
/// Get inheriting file system rights of this file descriptor.
///
/// # Return
/// Returns inheriting file system rights of this file descriptor.
pub fn fs_rights_inheriting(&self) -> wasi::Rights {
self.fs_rights_inheriting
}
/// Get file descriptor flags of this file descriptor.
///
/// # Return
/// Returns file descriptor flags of this file descriptor.
pub fn fs_flags(&self) -> wasi::Fdflags {
self.fs_flags
}
/// Set file descriptor flags of this file descriptor if allowed.
///
/// # Return
/// If successful, returns ().
/// Otherwise, returns a wasi::Errno.
pub fn set_fs_flags(&mut self, new_flags: wasi::Fdflags) -> Result<(), wasi::Errno> {
// Verify that file descriptor has right to set flags.
if self.fs_rights_base() & wasi::RIGHTS_FD_FDSTAT_SET_FLAGS == 0 {
return Err(wasi::ERRNO_ACCES);
}
self.fs_flags = new_flags;
Ok(())
}
/// Writes data from the given `buffer` to this file system node if allowed.
///
/// The number of bytes written is dictated by the length of the given `buffer`.
///
/// # Arguments
/// * `buffer`: the buffer from which data will be written.
///
/// # Return
/// If successful, returns the number of bytes written to this file system node.
/// Otherwise, returns a wasi::Errno.
/// NOTE: Returns wasi::ERRNO_NOBUFS on Theseus file write error.
pub fn write(&mut self, buffer: &[u8]) -> Result<usize, wasi::Errno> {
// Verify that file descriptor has right to write.
if self.fs_rights_base() & wasi::RIGHTS_FD_WRITE == 0 {
return Err(wasi::ERRNO_ACCES);
}
match self.theseus_file_or_dir.clone() {
FileOrDir::File(file_ref) => {
// Check flags for append mode.
let is_append_mode: bool = (self.fs_flags() & wasi::FDFLAGS_APPEND) != 0;
if is_append_mode {
// Write to end of file.
let end_of_file_offset: usize = file_ref.lock().len();
match file_ref.lock().write_at(buffer, end_of_file_offset) {
Ok(bytes_written) => Ok(bytes_written),
Err(_) => Err(wasi::ERRNO_NOBUFS),
}
} else {
// Write at offset of file and update offset.
let offset = self.offset;
match file_ref.lock().write_at(buffer, offset) {
Ok(bytes_written) => {
self.offset = self.offset.checked_add(bytes_written).unwrap();
Ok(bytes_written)
}
Err(_) => Err(wasi::ERRNO_NOBUFS),
}
}
}
FileOrDir::Dir { .. } => Err(wasi::ERRNO_ISDIR),
}
}
/// Reads data from this file system node into the given `buffer` if allowed.
///
/// The number of bytes read is dictated by the length of the given `buffer`.
///
/// # Arguments
/// * `buffer`: the buffer into which the data will be read.
///
/// # Return
/// If successful, returns the number of bytes read into this file system node.
/// Otherwise, returns a wasi::Errno.
pub fn read(&mut self, buffer: &mut [u8]) -> Result<usize, wasi::Errno> {
// Verify that file descriptor has right to read.
if self.fs_rights_base() & wasi::RIGHTS_FD_READ == 0 {
return Err(wasi::ERRNO_ACCES);
}
match self.theseus_file_or_dir.clone() {
FileOrDir::File(file_ref) => {
// Read at offset of file and update offset.
let offset = self.offset;
match file_ref.lock().read_at(buffer, offset) {
Ok(bytes_read) => {
self.offset = self.offset.checked_add(bytes_read).unwrap();
Ok(bytes_read)
}
Err(_) => Err(wasi::ERRNO_NOBUFS),
}
}
FileOrDir::Dir { .. } => Err(wasi::ERRNO_ISDIR),
}
}
/// Move the offset of this file system node.
///
/// # Arguments
/// * `offset`: the number of bytes to move.
/// * `whence`: the base from which the offset is relative.
///
/// # Return
/// If successful, returns the resulting offset of this file system node.
/// Otherwise, returns a wasi::Errno.
pub fn seek(
&mut self,
delta: wasi::Filedelta,
whence: wasi::Whence,
) -> Result<usize, wasi::Errno> {
// Verify that file descriptor has right to seek.
if self.fs_rights_base() & wasi::RIGHTS_FD_SEEK == 0 {
return Err(wasi::ERRNO_ACCES);
}
match self.theseus_file_or_dir.clone() {
FileOrDir::File(file_ref) => {
let max_offset: usize = file_ref.lock().len();
let signed_to_file_offset = |x: i64| -> usize {
cmp::min(usize::try_from(cmp::max(0, x)).unwrap(), max_offset)
};
let new_offset: usize = match whence {
wasi::WHENCE_CUR => {
signed_to_file_offset(i64::try_from(self.offset).unwrap() + delta)
}
wasi::WHENCE_END => {
signed_to_file_offset(i64::try_from(max_offset).unwrap() + delta)
}
wasi::WHENCE_SET => signed_to_file_offset(delta),
_ => {
return Err(wasi::ERRNO_SPIPE);
}
};
self.offset = new_offset;
Ok(new_offset)
}
FileOrDir::Dir { .. } => Err(wasi::ERRNO_ISDIR),
}
}
}
/// File descriptor table.
pub struct FileDescriptorTable {
/// HashMap from file descriptor number to POSIX-style file.
fd_table: HashMap<wasi::Fd, PosixNodeOrStdio>,
}
impl FileDescriptorTable {
/// Instantiates a new FileDescriptorTable with stdio entries filled.
///
/// # Returns
/// Returns a new FileDescriptorTable consisting of stdio entries.
pub fn new() -> FileDescriptorTable {
let mut fd_table = HashMap::new();
fd_table.insert(wasi::FD_STDIN, PosixNodeOrStdio::Stdin);
fd_table.insert(wasi::FD_STDOUT, PosixNodeOrStdio::Stdout);
fd_table.insert(wasi::FD_STDERR, PosixNodeOrStdio::Stderr);
FileDescriptorTable { fd_table }
}
/// Open file or directory at path in accordance to given open flags and insert in fd table.
///
/// # Arguments
/// * `path`: &str representing path of file or directory to open.
/// * `starting_dir`: Theseus directory from which to search path from.
/// * `lookup_flags`: flags determining behavior of path resolution.
/// * `open_flags`: flags determining behavior of opening a file or directory.
/// * `fs_rights`: rights applying to this file descriptor.
/// * `fs_rights_inheriting`: rights applying to inherting file descriptors.
/// * `fs_flags`: file descriptor flags.
///
/// # Return
/// If successful, returns resulting file descriptor number.
/// Otherwise, returns a wasi::Errno.
#[allow(clippy::too_many_arguments)]
pub fn open_path(
&mut self,
path: &str,
starting_dir: DirRef,
lookup_flags: wasi::Lookupflags,
open_flags: wasi::Oflags,
fs_rights_base: wasi::Rights,
fs_rights_inheriting: wasi::Rights,
fs_flags: wasi::Fdflags,
) -> Result<wasi::Fd, wasi::Errno> {
// NOTE: https://docs.rs/wasi/0.9.0+wasi-snapshot-preview1/wasi/constant.LOOKUPFLAGS_SYMLINK_FOLLOW.html
// Unused as symlinks are currently not implemented.
let _symlink_follow: bool = (lookup_flags & wasi::LOOKUPFLAGS_SYMLINK_FOLLOW) != 0;
// Parse open flags.
let create_file_if_no_exist: bool = (open_flags & wasi::OFLAGS_CREAT) != 0;
let fail_if_not_dir: bool = (open_flags & wasi::OFLAGS_DIRECTORY) != 0;
let fail_if_file_exists: bool = (open_flags & wasi::OFLAGS_EXCL) != 0;
let truncate_file_to_size_zero: bool = (open_flags & wasi::OFLAGS_TRUNC) != 0;
// Find first unused file descriptor number.
// TODO: Potentially can implement a more efficient search data structure.
let mut fd: wasi::Fd = FIRST_NONRESERVED_FD;
while self.fd_table.contains_key(&fd) {
fd += 1;
}
// Split path into parent directory path and base path.
let file_path: &Path = path.as_ref();
let parent_dir_path = file_path.parent().ok_or(wasi::ERRNO_NOENT)?;
let base_name = file_path.file_name().ok_or(wasi::ERRNO_NOENT)?;
let base_path: &Path = base_name.as_ref();
// Get parent directory.
let parent_dir: DirRef = match parent_dir_path.get(&starting_dir) {
Some(file_or_dir) => match file_or_dir {
FileOrDir::File { .. } => {
return Err(wasi::ERRNO_NOENT);
}
FileOrDir::Dir(dir_ref) => dir_ref,
},
None => {
return Err(wasi::ERRNO_NOENT);
}
};
// Open file or directory at path in accordance to open flags.
let opened_file_or_dir: FileOrDir = match base_path.get(&parent_dir) {
Some(file_or_dir) => match file_or_dir {
FileOrDir::File { .. } => {
if fail_if_file_exists {
return Err(wasi::ERRNO_EXIST);
} else if fail_if_not_dir {
return Err(wasi::ERRNO_NOTDIR);
} else if truncate_file_to_size_zero {
// HACK: Truncate file by overwriting file.
let new_file: FileRef =
MemFile::create(String::from(base_name), &parent_dir).unwrap();
FileOrDir::File(new_file)
} else {
file_or_dir
}
}
FileOrDir::Dir { .. } => file_or_dir,
},
None => {
if create_file_if_no_exist {
let new_file: FileRef =
MemFile::create(String::from(base_name), &parent_dir).unwrap();
FileOrDir::File(new_file)
} else {
return Err(wasi::ERRNO_NOENT);
}
}
};
// Insert POSIX-style file in file descriptor table with given rights and flags.
self.fd_table.insert(
fd,
PosixNodeOrStdio::Inode(PosixNode::new(
opened_file_or_dir,
fs_rights_base,
fs_rights_inheriting,
fs_flags,
)),
);
Ok(fd)
}
/// Close a given file descriptor if not standard I/O.
///
/// # Arguments
/// * `fd`: file descriptor number to be closed.
///
/// # Return
/// If successful, returns ().
/// Otherwise, returns a wasi::Errno.
pub fn close_fd(&mut self, fd: wasi::Fd) -> Result<(), wasi::Errno> {
if self.fd_table.contains_key(&fd)
&& fd != wasi::FD_STDIN
&& fd != wasi::FD_STDOUT
&& fd != wasi::FD_STDERR
{
self.fd_table.remove(&fd);
return Ok(());
}
Err(wasi::ERRNO_BADF)
}
/// Get POSIX-style file from file descriptor number.
///
/// # Arguments
/// * `fd`: file descriptor number to access.
///
/// # Return
/// Returns corresponding POSIX-style file if exists.
pub fn get_posix_node_or_stdio(&mut self, fd: wasi::Fd) -> Option<&mut PosixNodeOrStdio> {
self.fd_table.get_mut(&fd)
}
/// Get file system node from file descriptor number.
///
/// This method makes it easier to access an underlying file system node from a fd number.
///
/// # Arguments
/// * `fd`: file descriptor number to access.
///
/// # Return
/// Returns corresponding file system node if exists.
pub fn get_posix_node(&mut self, fd: wasi::Fd) -> Option<&mut PosixNode> {
if let Some(PosixNodeOrStdio::Inode(posix_node)) = self.get_posix_node_or_stdio(fd) {
Some(posix_node)
} else {
None
}
}
}