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shell(cat): read regular files synchronously in the builtin on POSIX #35337

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shell(cat): read regular files synchronously in the builtin on POSIX #35337

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295 changes: 194 additions & 101 deletions src/runtime/shell/builtin/cat.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -104,125 +104,173 @@ impl Cat {
Builtin::done(interp, cmd, exit_code)
}

/// `Some(yield)` if a chunk was enqueued on fd-backed stdout, `None` if written synchronously.
fn write_buf_to_stdout(interp: &Interpreter, cmd: NodeId, buf: &[u8]) -> Option<Yield> {
if let Some(safeguard) = Builtin::of(interp, cmd).stdout.needs_io() {
match &mut Self::state_mut(interp, cmd).state {
CatState::ExecStdin {
in_done,
chunks_queued,
..
}
| CatState::ExecFilepathArgs {
in_done,
chunks_queued,
..
} => {
*in_done = true;
*chunks_queued += 1;
}
_ => panic!("Invalid state"),
}
let child = ChildPtr::new(cmd, WriterTag::Builtin);
return Some(
Builtin::of_mut(interp, cmd)
.stdout
.enqueue(child, buf, safeguard),
);
}
let _ = Builtin::write_no_io(interp, cmd, IoKind::Stdout, buf);
None
}

pub(crate) fn next(interp: &Interpreter, cmd: NodeId) -> Yield {
// Read scalars, drop the borrow, then act.
enum Branch {
Stdin,
FileArg { args_start: usize, idx: usize },
WaitingErr,
}
let branch = match &Self::state_mut(interp, cmd).state {
CatState::Idle => panic!("Invalid state"),
CatState::ExecStdin { .. } => Branch::Stdin,
CatState::ExecFilepathArgs {
args_start, idx, ..
} => Branch::FileArg {
args_start: *args_start,
idx: *idx,
},
CatState::WaitingWriteErr => Branch::WaitingErr,
};
match branch {
Branch::Stdin => {
// Stdin doesn't need IO (captured/ignored): read it all
// synchronously and write straight to stdout.
let stdin_needs_io = Builtin::of(interp, cmd).stdin.needs_io();
if !stdin_needs_io {
if let CatState::ExecStdin { in_done, .. } =
&mut Self::state_mut(interp, cmd).state
{
*in_done = true;
loop {
let branch = match &Self::state_mut(interp, cmd).state {
CatState::Idle => panic!("Invalid state"),
CatState::ExecStdin { .. } => Branch::Stdin,
CatState::ExecFilepathArgs {
args_start, idx, ..
} => Branch::FileArg {
args_start: *args_start,
idx: *idx,
},
CatState::WaitingWriteErr => Branch::WaitingErr,
};
return match branch {
Branch::Stdin => {
// Stdin doesn't need IO (captured/ignored): read it all
// synchronously and write straight to stdout.
Comment thread
robobun marked this conversation as resolved.
let stdin_needs_io = Builtin::of(interp, cmd).stdin.needs_io();
if !stdin_needs_io {
// Copy stdin bytes so the &mut on `stdout`/`write_no_io`
// doesn't overlap a borrow of `stdin`.
Comment thread
robobun marked this conversation as resolved.
let buf = Builtin::read_stdin_no_io(interp, cmd).to_vec();
return Self::write_buf_to_stdout(interp, cmd, &buf)
.unwrap_or_else(|| Builtin::done(interp, cmd, 0));
}
// Copy stdin bytes so the &mut on `stdout`/`write_no_io`
// doesn't overlap a borrow of `stdin`.
let buf = Builtin::read_stdin_no_io(interp, cmd).to_vec();
if let Some(safeguard) = Builtin::of(interp, cmd).stdout.needs_io() {
let child = ChildPtr::new(cmd, WriterTag::Builtin);
return Builtin::of_mut(interp, cmd)
.stdout
.enqueue(child, &buf, safeguard);
// Clone the `Arc<IOReader>`
// out of `stdin` so we hold no borrow of `interp` across
// `start()` (which may re-enter via the raw interp backref).
Comment thread
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let interp_ptr: *mut Interpreter = interp.as_ctx_ptr();
let reader = match &Builtin::of(interp, cmd).stdin {
BuiltinInput::Fd(r) => Arc::clone(r),
_ => unreachable!("needs_io() returned true"),
};
// The fd stays owned by `Builtin::stdin`.
if let Some(result) = slurp_regular_file(reader.fd()) {
return match result {
Ok(buf) => Self::write_buf_to_stdout(interp, cmd, &buf)
.unwrap_or_else(|| Builtin::done(interp, cmd, 0)),
Err(e) => {
let buf = Builtin::task_error_to_string(interp, cmd, Kind::Cat, &e)
.to_vec();
Self::write_failing_error(interp, cmd, &buf, 1)
}
};
}
let _ = Builtin::write_no_io(interp, cmd, IoKind::Stdout, &buf);
return Builtin::done(interp, cmd, 0);
reader.set_interp(interp_ptr);
reader.add_reader(ReaderChildPtr {
node: cmd,
tag: ReaderTag::Cat,
});
reader.start()
}
// Clone the `Arc<IOReader>`
// out of `stdin` so we hold no borrow of `interp` across
// `start()` (which may re-enter via the raw interp backref).
let interp_ptr: *mut Interpreter = interp.as_ctx_ptr();
let reader = match &Builtin::of(interp, cmd).stdin {
BuiltinInput::Fd(r) => Arc::clone(r),
_ => unreachable!("needs_io() returned true"),
};
reader.set_interp(interp_ptr);
reader.add_reader(ReaderChildPtr {
node: cmd,
tag: ReaderTag::Cat,
});
reader.start()
}
Branch::FileArg { args_start, idx } => {
let argc = Builtin::of(interp, cmd).args_slice().len();
let n_files = argc - args_start;
if idx >= n_files {
// Drop the reader if any.
if let CatState::ExecFilepathArgs { reader, .. } =
&mut Self::state_mut(interp, cmd).state
Branch::FileArg { args_start, idx } => {
let argc = Builtin::of(interp, cmd).args_slice().len();
let n_files = argc - args_start;
if idx >= n_files {
// Drop the reader if any.
if let CatState::ExecFilepathArgs { reader, .. } =
&mut Self::state_mut(interp, cmd).state
{
*reader = None;
}
return Builtin::done(interp, cmd, 0);
}
if let CatState::ExecFilepathArgs {
reader,
chunks_done,
chunks_queued,
in_done,
out_done,
..
} = &mut Self::state_mut(interp, cmd).state
{
*reader = None;
*chunks_done = 0;
*chunks_queued = 0;
*in_done = false;
*out_done = false;
}
return Builtin::done(interp, cmd, 0);
}
if let CatState::ExecFilepathArgs { reader, .. } =
&mut Self::state_mut(interp, cmd).state
{
*reader = None;
}

let path = Builtin::of(interp, cmd).arg_zstr(args_start + idx);
let path = Builtin::of(interp, cmd).arg_zstr(args_start + idx);

if let CatState::ExecFilepathArgs { idx: i, .. } =
&mut Self::state_mut(interp, cmd).state
{
*i += 1;
}
if let CatState::ExecFilepathArgs { idx: i, .. } =
&mut Self::state_mut(interp, cmd).state
{
*i += 1;
}

let dir = Builtin::cwd(interp, cmd);
let fd = match shell_openat(dir, path, bun_sys::O::RDONLY, 0) {
Ok(fd) => fd,
Err(e) => {
let buf =
Builtin::task_error_to_string(interp, cmd, Kind::Cat, &e).to_vec();
// The reader was already taken to `None` above.
return Self::write_failing_error(interp, cmd, &buf, 1);
}
};

let dir = Builtin::cwd(interp, cmd);
let fd = match shell_openat(dir, path, bun_sys::O::RDONLY, 0) {
Ok(fd) => fd,
Err(e) => {
let buf =
Builtin::task_error_to_string(interp, cmd, Kind::Cat, &e).to_vec();
// The reader was already taken to `None` above.
return Self::write_failing_error(interp, cmd, &buf, 1);
if let Some(result) = slurp_regular_file(fd) {
let _ = bun_sys::close(fd);
match result {
Ok(buf) => match Self::write_buf_to_stdout(interp, cmd, &buf) {
Some(y) => return y,
None => continue,
},
Err(e) => {
let buf = Builtin::task_error_to_string(interp, cmd, Kind::Cat, &e)
.to_vec();
return Self::write_failing_error(interp, cmd, &buf, 1);
}
}
}
};

let evtloop = Builtin::event_loop(interp, cmd);
let interp_ptr: *mut Interpreter = interp.as_ctx_ptr();
let reader = IOReader::init(fd, evtloop);
reader.set_interp(interp_ptr);
if let CatState::ExecFilepathArgs {
reader: slot,
chunks_done,
chunks_queued,
in_done,
out_done,
..
} = &mut Self::state_mut(interp, cmd).state
{
*chunks_done = 0;
*chunks_queued = 0;
*in_done = false;
*out_done = false;
*slot = Some(Arc::clone(&reader));
let evtloop = Builtin::event_loop(interp, cmd);
let interp_ptr: *mut Interpreter = interp.as_ctx_ptr();
let reader = IOReader::init(fd, evtloop);
reader.set_interp(interp_ptr);
if let CatState::ExecFilepathArgs { reader: slot, .. } =
&mut Self::state_mut(interp, cmd).state
{
*slot = Some(Arc::clone(&reader));
}
reader.add_reader(ReaderChildPtr {
node: cmd,
tag: ReaderTag::Cat,
});
reader.start()
}
reader.add_reader(ReaderChildPtr {
node: cmd,
tag: ReaderTag::Cat,
});
reader.start()
}
Branch::WaitingErr => Yield::failed(),
Branch::WaitingErr => Yield::failed(),
};
}
}

Expand Down Expand Up @@ -372,7 +420,7 @@ impl Cat {
} => {
*in_done = true;
if errno != 0 {
if *out_done || !stdout_needs_io {
if *out_done || *chunks_done >= *chunks_queued || !stdout_needs_io {
Comment thread
robobun marked this conversation as resolved.
// Drop the reader ref.
*reader = None;
Step::Done(errno)
Expand Down Expand Up @@ -402,6 +450,51 @@ impl Cat {
}
}

/// Reads an `S_IFREG` fd to EOF; `None` for other fd types (Linux epoll rejects regular files).
#[allow(unused_variables)]
fn slurp_regular_file(fd: bun_sys::Fd) -> Option<bun_sys::Result<Vec<u8>>> {
#[cfg(unix)]
{
let st = match bun_sys::fstat(fd) {
Ok(st) => st,
Err(e) => return Some(Err(e)),
};
if !bun_sys::S::ISREG(st.st_mode as _) {
return None;
}
let size_hint = usize::try_from(st.st_size).unwrap_or(0);
let mut buf: Vec<u8> = Vec::new();
if buf.try_reserve(size_hint.saturating_add(1)).is_err() {
return Some(Err(bun_sys::Error::from_code(
bun_sys::E::ENOMEM,
bun_sys::Tag::read,
)));
}
loop {
if buf.len() == buf.capacity() && buf.try_reserve(64 * 1024).is_err() {
return Some(Err(bun_sys::Error::from_code(
bun_sys::E::ENOMEM,
bun_sys::Tag::read,
)));
}
// SAFETY: `bun_sys::read` only writes initialised bytes into the
// prefix it reports; `commit_spare` exposes exactly that prefix.
let spare = unsafe { bun_core::vec::spare_bytes_mut(&mut buf) };
match bun_sys::read(fd, spare) {
Ok(0) => return Some(Ok(buf)),
// SAFETY: `n` bytes were just initialised by the syscall.
Ok(n) => unsafe { bun_core::vec::commit_spare(&mut buf, n) },
Err(e) if e.is_retry() => continue,
Err(e) => return Some(Err(e)),
}
}
}
#[cfg(windows)]
{
None
}
}

#[derive(Clone, Copy, Default)]
pub struct Opts {}

Expand Down
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