1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607
use crate::bindings::filesystem::types;
use crate::runtime::{spawn_blocking, AbortOnDropJoinHandle};
use crate::{
HostInputStream, HostOutputStream, StreamError, StreamResult, Subscribe, TrappableError,
};
use anyhow::anyhow;
use bytes::{Bytes, BytesMut};
use std::io;
use std::mem;
use std::sync::Arc;
pub type FsResult<T> = Result<T, FsError>;
pub type FsError = TrappableError<types::ErrorCode>;
impl From<wasmtime::component::ResourceTableError> for FsError {
fn from(error: wasmtime::component::ResourceTableError) -> Self {
Self::trap(error)
}
}
impl From<io::Error> for FsError {
fn from(error: io::Error) -> Self {
types::ErrorCode::from(error).into()
}
}
pub enum Descriptor {
File(File),
Dir(Dir),
}
impl Descriptor {
pub fn file(&self) -> Result<&File, types::ErrorCode> {
match self {
Descriptor::File(f) => Ok(f),
Descriptor::Dir(_) => Err(types::ErrorCode::BadDescriptor),
}
}
pub fn dir(&self) -> Result<&Dir, types::ErrorCode> {
match self {
Descriptor::Dir(d) => Ok(d),
Descriptor::File(_) => Err(types::ErrorCode::NotDirectory),
}
}
pub fn is_file(&self) -> bool {
match self {
Descriptor::File(_) => true,
Descriptor::Dir(_) => false,
}
}
pub fn is_dir(&self) -> bool {
match self {
Descriptor::File(_) => false,
Descriptor::Dir(_) => true,
}
}
}
bitflags::bitflags! {
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub struct FilePerms: usize {
const READ = 0b1;
const WRITE = 0b10;
}
}
bitflags::bitflags! {
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub struct OpenMode: usize {
const READ = 0b1;
const WRITE = 0b10;
}
}
#[derive(Clone)]
pub struct File {
/// The operating system File this struct is mediating access to.
///
/// Wrapped in an Arc because the same underlying file is used for
/// implementing the stream types. A copy is also needed for
/// [`spawn_blocking`].
///
/// [`spawn_blocking`]: Self::spawn_blocking
pub file: Arc<cap_std::fs::File>,
/// Permissions to enforce on access to the file. These permissions are
/// specified by a user of the `crate::WasiCtxBuilder`, and are
/// enforced prior to any enforced by the underlying operating system.
pub perms: FilePerms,
/// The mode the file was opened under: bits for reading, and writing.
/// Required to correctly report the DescriptorFlags, because cap-std
/// doesn't presently provide a cross-platform equivalent of reading the
/// oflags back out using fcntl.
pub open_mode: OpenMode,
allow_blocking_current_thread: bool,
}
impl File {
pub fn new(
file: cap_std::fs::File,
perms: FilePerms,
open_mode: OpenMode,
allow_blocking_current_thread: bool,
) -> Self {
Self {
file: Arc::new(file),
perms,
open_mode,
allow_blocking_current_thread,
}
}
/// Execute the blocking `body` function.
///
/// Depending on how the WasiCtx was configured, the body may either be:
/// - Executed directly on the current thread. In this case the `async`
/// signature of this method is effectively a lie and the returned
/// Future will always be immediately Ready. Or:
/// - Spawned on a background thread using [`tokio::task::spawn_blocking`]
/// and immediately awaited.
///
/// Intentionally blocking the executor thread might seem unorthodox, but is
/// not actually a problem for specific workloads. See:
/// - [`crate::WasiCtxBuilder::allow_blocking_current_thread`]
/// - [Poor performance of wasmtime file I/O maybe because tokio](https://github.com/bytecodealliance/wasmtime/issues/7973)
/// - [Implement opt-in for enabling WASI to block the current thread](https://github.com/bytecodealliance/wasmtime/pull/8190)
pub(crate) async fn run_blocking<F, R>(&self, body: F) -> R
where
F: FnOnce(&cap_std::fs::File) -> R + Send + 'static,
R: Send + 'static,
{
match self.as_blocking_file() {
Some(file) => body(file),
None => self.spawn_blocking(body).await,
}
}
pub(crate) fn spawn_blocking<F, R>(&self, body: F) -> AbortOnDropJoinHandle<R>
where
F: FnOnce(&cap_std::fs::File) -> R + Send + 'static,
R: Send + 'static,
{
let f = self.file.clone();
spawn_blocking(move || body(&f))
}
/// Returns `Some` when the current thread is allowed to block in filesystem
/// operations, and otherwise returns `None` to indicate that
/// `spawn_blocking` must be used.
pub(crate) fn as_blocking_file(&self) -> Option<&cap_std::fs::File> {
if self.allow_blocking_current_thread {
Some(&self.file)
} else {
None
}
}
}
bitflags::bitflags! {
/// Permission bits for operating on a directory.
///
/// Directories can be limited to being readonly. This will restrict what
/// can be done with them, for example preventing creation of new files.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub struct DirPerms: usize {
/// This directory can be read, for example its entries can be iterated
/// over and files can be opened.
const READ = 0b1;
/// This directory can be mutated, for example by creating new files
/// within it.
const MUTATE = 0b10;
}
}
#[derive(Clone)]
pub struct Dir {
/// The operating system file descriptor this struct is mediating access
/// to.
///
/// Wrapped in an Arc because a copy is needed for [`spawn_blocking`].
///
/// [`spawn_blocking`]: Self::spawn_blocking
pub dir: Arc<cap_std::fs::Dir>,
/// Permissions to enforce on access to this directory. These permissions
/// are specified by a user of the `crate::WasiCtxBuilder`, and
/// are enforced prior to any enforced by the underlying operating system.
///
/// These permissions are also enforced on any directories opened under
/// this directory.
pub perms: DirPerms,
/// Permissions to enforce on any files opened under this directory.
pub file_perms: FilePerms,
/// The mode the directory was opened under: bits for reading, and writing.
/// Required to correctly report the DescriptorFlags, because cap-std
/// doesn't presently provide a cross-platform equivalent of reading the
/// oflags back out using fcntl.
pub open_mode: OpenMode,
allow_blocking_current_thread: bool,
}
impl Dir {
pub fn new(
dir: cap_std::fs::Dir,
perms: DirPerms,
file_perms: FilePerms,
open_mode: OpenMode,
allow_blocking_current_thread: bool,
) -> Self {
Dir {
dir: Arc::new(dir),
perms,
file_perms,
open_mode,
allow_blocking_current_thread,
}
}
/// Execute the blocking `body` function.
///
/// Depending on how the WasiCtx was configured, the body may either be:
/// - Executed directly on the current thread. In this case the `async`
/// signature of this method is effectively a lie and the returned
/// Future will always be immediately Ready. Or:
/// - Spawned on a background thread using [`tokio::task::spawn_blocking`]
/// and immediately awaited.
///
/// Intentionally blocking the executor thread might seem unorthodox, but is
/// not actually a problem for specific workloads. See:
/// - [`crate::WasiCtxBuilder::allow_blocking_current_thread`]
/// - [Poor performance of wasmtime file I/O maybe because tokio](https://github.com/bytecodealliance/wasmtime/issues/7973)
/// - [Implement opt-in for enabling WASI to block the current thread](https://github.com/bytecodealliance/wasmtime/pull/8190)
pub(crate) async fn run_blocking<F, R>(&self, body: F) -> R
where
F: FnOnce(&cap_std::fs::Dir) -> R + Send + 'static,
R: Send + 'static,
{
if self.allow_blocking_current_thread {
body(&self.dir)
} else {
let d = self.dir.clone();
spawn_blocking(move || body(&d)).await
}
}
}
pub struct FileInputStream {
file: File,
position: u64,
state: ReadState,
}
enum ReadState {
Idle,
Waiting(AbortOnDropJoinHandle<ReadState>),
DataAvailable(Bytes),
Error(io::Error),
Closed,
}
impl FileInputStream {
pub fn new(file: &File, position: u64) -> Self {
Self {
file: file.clone(),
position,
state: ReadState::Idle,
}
}
fn blocking_read(file: &cap_std::fs::File, offset: u64, size: usize) -> ReadState {
use system_interface::fs::FileIoExt;
let mut buf = BytesMut::zeroed(size);
loop {
match file.read_at(&mut buf, offset) {
Ok(0) => return ReadState::Closed,
Ok(n) => {
buf.truncate(n);
return ReadState::DataAvailable(buf.freeze());
}
Err(e) if e.kind() == std::io::ErrorKind::Interrupted => {
// Try again, continue looping
}
Err(e) => return ReadState::Error(e),
}
}
}
/// Wait for existing background task to finish, without starting any new background reads.
async fn wait_ready(&mut self) {
match &mut self.state {
ReadState::Waiting(task) => {
self.state = task.await;
}
_ => {}
}
}
}
#[async_trait::async_trait]
impl HostInputStream for FileInputStream {
fn read(&mut self, size: usize) -> StreamResult<Bytes> {
match &mut self.state {
ReadState::Idle => {
if size == 0 {
return Ok(Bytes::new());
}
let p = self.position;
self.state = ReadState::Waiting(
self.file
.spawn_blocking(move |f| Self::blocking_read(f, p, size)),
);
Ok(Bytes::new())
}
ReadState::DataAvailable(b) => {
let min_len = b.len().min(size);
let chunk = b.split_to(min_len);
if b.len() == 0 {
self.state = ReadState::Idle;
}
self.position += min_len as u64;
Ok(chunk)
}
ReadState::Waiting(_) => Ok(Bytes::new()),
ReadState::Error(_) => match mem::replace(&mut self.state, ReadState::Closed) {
ReadState::Error(e) => Err(StreamError::LastOperationFailed(e.into())),
_ => unreachable!(),
},
ReadState::Closed => Err(StreamError::Closed),
}
}
/// Specialized blocking_* variant to bypass tokio's task spawning & joining
/// overhead on synchronous file I/O.
async fn blocking_read(&mut self, size: usize) -> StreamResult<Bytes> {
self.wait_ready().await;
// Before we defer to the regular `read`, make sure it has data ready to go:
if let ReadState::Idle = self.state {
let p = self.position;
self.state = self
.file
.run_blocking(move |f| Self::blocking_read(f, p, size))
.await;
}
self.read(size)
}
async fn cancel(&mut self) {
match mem::replace(&mut self.state, ReadState::Closed) {
ReadState::Waiting(task) => {
// The task was created using `spawn_blocking`, so unless we're
// lucky enough that the task hasn't started yet, the abort
// signal won't have any effect and we're forced to wait for it
// to run to completion.
// From the guest's point of view, `input-stream::drop` then
// appears to block. Certainly less than ideal, but arguably still
// better than letting the guest rack up an unbounded number of
// background tasks. Also, the guest is only blocked if
// the stream was dropped mid-read, which we don't expect to
// occur frequently.
task.cancel().await;
}
_ => {}
}
}
}
#[async_trait::async_trait]
impl Subscribe for FileInputStream {
async fn ready(&mut self) {
if let ReadState::Idle = self.state {
// The guest hasn't initiated any read, but is nonetheless waiting
// for data to be available. We'll start a read for them:
const DEFAULT_READ_SIZE: usize = 4096;
let p = self.position;
self.state = ReadState::Waiting(
self.file
.spawn_blocking(move |f| Self::blocking_read(f, p, DEFAULT_READ_SIZE)),
);
}
self.wait_ready().await
}
}
#[derive(Clone, Copy)]
pub(crate) enum FileOutputMode {
Position(u64),
Append,
}
pub(crate) struct FileOutputStream {
file: File,
mode: FileOutputMode,
state: OutputState,
}
enum OutputState {
Ready,
/// Allows join future to be awaited in a cancellable manner. Gone variant indicates
/// no task is currently outstanding.
Waiting(AbortOnDropJoinHandle<io::Result<usize>>),
/// The last I/O operation failed with this error.
Error(io::Error),
Closed,
}
impl FileOutputStream {
pub fn write_at(file: &File, position: u64) -> Self {
Self {
file: file.clone(),
mode: FileOutputMode::Position(position),
state: OutputState::Ready,
}
}
pub fn append(file: &File) -> Self {
Self {
file: file.clone(),
mode: FileOutputMode::Append,
state: OutputState::Ready,
}
}
fn blocking_write(
file: &cap_std::fs::File,
mut buf: Bytes,
mode: FileOutputMode,
) -> io::Result<usize> {
use system_interface::fs::FileIoExt;
match mode {
FileOutputMode::Position(mut p) => {
let mut total = 0;
loop {
let nwritten = file.write_at(buf.as_ref(), p)?;
// afterwards buf contains [nwritten, len):
let _ = buf.split_to(nwritten);
p += nwritten as u64;
total += nwritten;
if buf.is_empty() {
break;
}
}
Ok(total)
}
FileOutputMode::Append => {
let mut total = 0;
loop {
let nwritten = file.append(buf.as_ref())?;
let _ = buf.split_to(nwritten);
total += nwritten;
if buf.is_empty() {
break;
}
}
Ok(total)
}
}
}
}
// FIXME: configurable? determine from how much space left in file?
const FILE_WRITE_CAPACITY: usize = 1024 * 1024;
#[async_trait::async_trait]
impl HostOutputStream for FileOutputStream {
fn write(&mut self, buf: Bytes) -> Result<(), StreamError> {
match self.state {
OutputState::Ready => {}
OutputState::Closed => return Err(StreamError::Closed),
OutputState::Waiting(_) | OutputState::Error(_) => {
// a write is pending - this call was not permitted
return Err(StreamError::Trap(anyhow!(
"write not permitted: check_write not called first"
)));
}
}
let m = self.mode;
self.state = OutputState::Waiting(
self.file
.spawn_blocking(move |f| Self::blocking_write(f, buf, m)),
);
Ok(())
}
/// Specialized blocking_* variant to bypass tokio's task spawning & joining
/// overhead on synchronous file I/O.
async fn blocking_write_and_flush(&mut self, buf: Bytes) -> StreamResult<()> {
self.ready().await;
match self.state {
OutputState::Ready => {}
OutputState::Closed => return Err(StreamError::Closed),
OutputState::Error(_) => match mem::replace(&mut self.state, OutputState::Closed) {
OutputState::Error(e) => return Err(StreamError::LastOperationFailed(e.into())),
_ => unreachable!(),
},
OutputState::Waiting(_) => unreachable!("we've just waited for readiness"),
}
let m = self.mode;
match self
.file
.run_blocking(move |f| Self::blocking_write(f, buf, m))
.await
{
Ok(nwritten) => {
if let FileOutputMode::Position(ref mut p) = &mut self.mode {
*p += nwritten as u64;
}
self.state = OutputState::Ready;
Ok(())
}
Err(e) => {
self.state = OutputState::Closed;
Err(StreamError::LastOperationFailed(e.into()))
}
}
}
fn flush(&mut self) -> Result<(), StreamError> {
match self.state {
// Only userland buffering of file writes is in the blocking task,
// so there's nothing extra that needs to be done to request a
// flush.
OutputState::Ready | OutputState::Waiting(_) => Ok(()),
OutputState::Closed => Err(StreamError::Closed),
OutputState::Error(_) => match mem::replace(&mut self.state, OutputState::Closed) {
OutputState::Error(e) => Err(StreamError::LastOperationFailed(e.into())),
_ => unreachable!(),
},
}
}
fn check_write(&mut self) -> Result<usize, StreamError> {
match self.state {
OutputState::Ready => Ok(FILE_WRITE_CAPACITY),
OutputState::Closed => Err(StreamError::Closed),
OutputState::Error(_) => match mem::replace(&mut self.state, OutputState::Closed) {
OutputState::Error(e) => Err(StreamError::LastOperationFailed(e.into())),
_ => unreachable!(),
},
OutputState::Waiting(_) => Ok(0),
}
}
async fn cancel(&mut self) {
match mem::replace(&mut self.state, OutputState::Closed) {
OutputState::Waiting(task) => {
// The task was created using `spawn_blocking`, so unless we're
// lucky enough that the task hasn't started yet, the abort
// signal won't have any effect and we're forced to wait for it
// to run to completion.
// From the guest's point of view, `output-stream::drop` then
// appears to block. Certainly less than ideal, but arguably still
// better than letting the guest rack up an unbounded number of
// background tasks. Also, the guest is only blocked if
// the stream was dropped mid-write, which we don't expect to
// occur frequently.
task.cancel().await;
}
_ => {}
}
}
}
#[async_trait::async_trait]
impl Subscribe for FileOutputStream {
async fn ready(&mut self) {
if let OutputState::Waiting(task) = &mut self.state {
self.state = match task.await {
Ok(nwritten) => {
if let FileOutputMode::Position(ref mut p) = &mut self.mode {
*p += nwritten as u64;
}
OutputState::Ready
}
Err(e) => OutputState::Error(e),
};
}
}
}
pub struct ReaddirIterator(
std::sync::Mutex<Box<dyn Iterator<Item = FsResult<types::DirectoryEntry>> + Send + 'static>>,
);
impl ReaddirIterator {
pub(crate) fn new(
i: impl Iterator<Item = FsResult<types::DirectoryEntry>> + Send + 'static,
) -> Self {
ReaddirIterator(std::sync::Mutex::new(Box::new(i)))
}
pub(crate) fn next(&self) -> FsResult<Option<types::DirectoryEntry>> {
self.0.lock().unwrap().next().transpose()
}
}
impl IntoIterator for ReaddirIterator {
type Item = FsResult<types::DirectoryEntry>;
type IntoIter = Box<dyn Iterator<Item = Self::Item> + Send>;
fn into_iter(self) -> Self::IntoIter {
self.0.into_inner().unwrap()
}
}