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Implement path_open. (bytecodealliance#18)
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* Implement `path_open`.

* Implement `fd_close`, and finish `path_open`.

* Stub out `close` in the host impl.
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@sunfishcode
sunfishcode committed Dec 7, 2022
1 parent 3477cd0 commit 91fff49
Showing 1 changed file with 136 additions and 11 deletions.
147 changes: 136 additions & 11 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,14 @@ fn unwrap<T>(maybe: Option<T>) -> T {
}
}

fn unwrap_result<T, E>(result: Result<T, E>) -> T {
if let Ok(value) = result {
value
} else {
unreachable()
}
}

#[no_mangle]
pub unsafe extern "C" fn cabi_import_realloc(
old_ptr: *mut u8,
Expand Down Expand Up @@ -288,7 +296,23 @@ pub unsafe extern "C" fn fd_allocate(fd: Fd, offset: Filesize, len: Filesize) ->
/// Note: This is similar to `close` in POSIX.
#[no_mangle]
pub unsafe extern "C" fn fd_close(fd: Fd) -> Errno {
unreachable()
State::with_mut(|state| {
let closed = state.closed;
let desc = state.get_mut(fd)?;

match desc {
Descriptor::File(file) => {
wasi_filesystem::close(file.fd);
}
Descriptor::Log => {}
Descriptor::Socket(_) => unreachable(),
Descriptor::Closed(_) => return Err(ERRNO_BADF),
}

*desc = Descriptor::Closed(closed);
state.closed = Some(fd);
Ok(())
})
}

/// Synchronize the data of a file to disk.
Expand Down Expand Up @@ -370,7 +394,7 @@ pub unsafe extern "C" fn fd_fdstat_get(fd: Fd, stat: *mut Fdstat) -> Errno {
}
// TODO: Handle socket case here once `wasi-tcp` has been fleshed out
Descriptor::Socket(_) => unreachable(),
Descriptor::Closed => Err(ERRNO_BADF),
Descriptor::Closed(_) => Err(ERRNO_BADF),
})
}

Expand Down Expand Up @@ -577,7 +601,7 @@ pub unsafe extern "C" fn fd_pwrite(
}
// TODO: Handle socket case here once `wasi-tcp` has been fleshed out
Descriptor::Socket(_) => unreachable(),
Descriptor::Closed => Err(ERRNO_BADF),
Descriptor::Closed(_) => Err(ERRNO_BADF),
})
}

Expand Down Expand Up @@ -741,7 +765,7 @@ pub unsafe extern "C" fn fd_write(
}
// TODO: Handle socket case here once `wasi-tcp` has been fleshed out
Descriptor::Socket(_) => unreachable(),
Descriptor::Closed => Err(ERRNO_BADF),
Descriptor::Closed(_) => Err(ERRNO_BADF),
})
}

Expand Down Expand Up @@ -887,7 +911,49 @@ pub unsafe extern "C" fn path_open(
fdflags: Fdflags,
opened_fd: *mut Fd,
) -> Errno {
unreachable()
drop(fs_rights_inheriting);

let path = slice::from_raw_parts(path_ptr, path_len);
let at_flags = at_flags_from_lookupflags(dirflags);
let o_flags = o_flags_from_oflags(oflags);
let flags = flags_from_descriptor_flags(fs_rights_base, fdflags);
let mode = wasi_filesystem::Mode::READABLE | wasi_filesystem::Mode::WRITEABLE;

State::with_mut(|state| {
let desc = state.get_mut(fd)?;

let file = state.get_dir(fd)?;
let result = wasi_filesystem::open_at(file.fd, at_flags, path, o_flags, flags, mode)?;
let desc = Descriptor::File(File {
fd: result,
position: Cell::new(0),
});

let fd = match state.closed {
// No free fds; create a new one.
None => match state.push_desc(desc) {
Ok(new) => new,
Err(err) => {
wasi_filesystem::close(result);
return Err(err);
}
},
// `recycle_fd` is a free fd.
Some(recycle_fd) => {
let recycle_desc = unwrap_result(state.get_mut(recycle_fd));
let next_closed = match recycle_desc {
Descriptor::Closed(next) => *next,
_ => unreachable(),
};
*recycle_desc = desc;
state.closed = next_closed;
recycle_fd
}
};

*opened_fd = fd;
Ok(())
})
}

/// Read the contents of a symbolic link.
Expand Down Expand Up @@ -1305,6 +1371,52 @@ fn at_flags_from_lookupflags(flags: Lookupflags) -> wasi_filesystem::AtFlags {
}
}

fn o_flags_from_oflags(flags: Oflags) -> wasi_filesystem::OFlags {
let mut o_flags = wasi_filesystem::OFlags::empty();
if flags & OFLAGS_CREAT == OFLAGS_CREAT {
o_flags |= wasi_filesystem::OFlags::CREATE;
}
if flags & OFLAGS_DIRECTORY == OFLAGS_DIRECTORY {
o_flags |= wasi_filesystem::OFlags::DIRECTORY;
}
if flags & OFLAGS_EXCL == OFLAGS_EXCL {
o_flags |= wasi_filesystem::OFlags::EXCL;
}
if flags & OFLAGS_TRUNC == OFLAGS_TRUNC {
o_flags |= wasi_filesystem::OFlags::TRUNC;
}
o_flags
}

fn flags_from_descriptor_flags(
rights: Rights,
fdflags: Fdflags,
) -> wasi_filesystem::DescriptorFlags {
let mut flags = wasi_filesystem::DescriptorFlags::empty();
if rights & wasi::RIGHTS_FD_READ == wasi::RIGHTS_FD_READ {
flags |= wasi_filesystem::DescriptorFlags::READ;
}
if rights & wasi::RIGHTS_FD_WRITE == wasi::RIGHTS_FD_WRITE {
flags |= wasi_filesystem::DescriptorFlags::WRITE;
}
if fdflags & wasi::FDFLAGS_SYNC == wasi::FDFLAGS_SYNC {
flags |= wasi_filesystem::DescriptorFlags::SYNC;
}
if fdflags & wasi::FDFLAGS_DSYNC == wasi::FDFLAGS_DSYNC {
flags |= wasi_filesystem::DescriptorFlags::DSYNC;
}
if fdflags & wasi::FDFLAGS_RSYNC == wasi::FDFLAGS_RSYNC {
flags |= wasi_filesystem::DescriptorFlags::RSYNC;
}
if fdflags & wasi::FDFLAGS_APPEND == wasi::FDFLAGS_APPEND {
flags |= wasi_filesystem::DescriptorFlags::APPEND;
}
if fdflags & wasi::FDFLAGS_NONBLOCK == wasi::FDFLAGS_NONBLOCK {
flags |= wasi_filesystem::DescriptorFlags::NONBLOCK;
}
flags
}

impl From<wasi_filesystem::Errno> for Errno {
#[inline(never)] // Disable inlining as this is bulky and relatively cold.
fn from(err: wasi_filesystem::Errno) -> Errno {
Expand Down Expand Up @@ -1390,7 +1502,7 @@ fn black_box(x: Errno) -> Errno {

#[repr(C)]
pub enum Descriptor {
Closed,
Closed(Option<Fd>),
File(File),
Socket(wasi_tcp::Socket),
Log,
Expand Down Expand Up @@ -1422,6 +1534,9 @@ struct State {
ndescriptors: u16,
descriptors: MaybeUninit<[Descriptor; MAX_DESCRIPTORS]>,

/// Points to the head of a free-list of closed file descriptors.
closed: Option<Fd>,

/// Auxiliary storage to handle the `path_readlink` function.
path_buf: UnsafeCell<MaybeUninit<[u8; PATH_MAX]>>,

Expand Down Expand Up @@ -1451,7 +1566,7 @@ const fn command_data_size() -> usize {
start -= size_of::<Descriptor>() * MAX_DESCRIPTORS;

// Remove miscellaneous metadata also stored in state.
start -= 5 * size_of::<usize>();
start -= 7 * size_of::<usize>();

// Everything else is the `command_data` allocation.
start
Expand Down Expand Up @@ -1514,6 +1629,7 @@ impl State {
buffer_ptr: Cell::new(null_mut()),
buffer_len: Cell::new(0),
ndescriptors: 0,
closed: None,
descriptors: MaybeUninit::uninit(),
path_buf: UnsafeCell::new(MaybeUninit::uninit()),
command_data: MaybeUninit::uninit(),
Expand All @@ -1529,7 +1645,7 @@ impl State {
let descriptors = self.descriptors.as_mut_ptr();
let ndescriptors = usize::try_from(self.ndescriptors).unwrap();
if ndescriptors >= (*descriptors).len() {
return Err(ERRNO_INVAL);
return Err(ERRNO_NOMEM);
}
ptr::addr_of_mut!((*descriptors)[ndescriptors]).write(desc);
self.ndescriptors += 1;
Expand All @@ -1540,7 +1656,16 @@ impl State {
fn get(&self, fd: Fd) -> Result<&Descriptor, Errno> {
let index = usize::try_from(fd).unwrap();
if index < usize::try_from(self.ndescriptors).unwrap() {
unsafe { (*self.descriptors.as_ptr()).get(index).ok_or(ERRNO_BADF) }
unsafe { Ok(unwrap((*self.descriptors.as_ptr()).get(index))) }
} else {
Err(ERRNO_BADF)
}
}

fn get_mut(&mut self, fd: Fd) -> Result<&mut Descriptor, Errno> {
let index = usize::try_from(fd).unwrap();
if index < usize::try_from(self.ndescriptors).unwrap() {
unsafe { Ok(unwrap((*self.descriptors.as_mut_ptr()).get_mut(index))) }
} else {
Err(ERRNO_BADF)
}
Expand All @@ -1550,15 +1675,15 @@ impl State {
match self.get(fd)? {
Descriptor::File(file) => Ok(file),
Descriptor::Log | Descriptor::Socket(_) => Err(error),
Descriptor::Closed => Err(ERRNO_BADF),
Descriptor::Closed(_) => Err(ERRNO_BADF),
}
}

fn get_socket(&self, fd: Fd) -> Result<wasi_tcp::Socket, Errno> {
match self.get(fd)? {
Descriptor::Socket(socket) => Ok(*socket),
Descriptor::Log | Descriptor::File(_) => Err(ERRNO_INVAL),
Descriptor::Closed => Err(ERRNO_BADF),
Descriptor::Closed(_) => Err(ERRNO_BADF),
}
}

Expand Down

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