f10n/sdk/lib/fdio/unsafe.h.md

# \<lib/fdio/unsafe.h\> in fdio

[Header source code](https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main/sdk/lib/fdio/include/lib/fdio/unsafe.h)

## fdio_unsafe_borrow_channel(…) {:#fdio_unsafe_borrow_channel}

[Declaration source code](https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main/sdk/lib/fdio/include/lib/fdio/unsafe.h#31)

<pre class="devsite-disable-click-to-copy">
<span class="typ">zx_handle_t</span> <b>fdio_unsafe_borrow_channel</b>(<span class="typ">fdio_t *</span> io);
</pre>

Returns the handle corresponding to the underlying fdio, if there is one. Returns
ZX_HANDLE_INVALID otherwise.

Since this handle is borrowed from the underlying fdio_t, it is unsafe to close it or use it
after fdio_unsafe_release is called.


## fdio_unsafe_fd_to_io(…) {:#fdio_unsafe_fd_to_io}

[Declaration source code](https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main/sdk/lib/fdio/include/lib/fdio/unsafe.h#24)

<pre class="devsite-disable-click-to-copy">
<span class="typ">fdio_t *</span> <b>fdio_unsafe_fd_to_io</b>(<span class="typ">int</span> fd);
</pre>

This looks up a file descriptor, and if it exists, upreferences the fdio_t under it and returns
that. fdio_unsafe_release() must be called later to release the reference.

If the fd does not exist, it returns NULL


## fdio_unsafe_release(…) {:#fdio_unsafe_release}

[Declaration source code](https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main/sdk/lib/fdio/include/lib/fdio/unsafe.h#35)

<pre class="devsite-disable-click-to-copy">
<span class="typ">void</span> <b>fdio_unsafe_release</b>(<span class="typ">fdio_t *</span> io);
</pre>

Releases a reference on a fdio_t.  Used to "return" a fdio_t obtained from fdio_unsafe_fd_to_io()
when you're done with it.


## fdio_unsafe_wait_begin(…) {:#fdio_unsafe_wait_begin}

[Declaration source code](https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main/sdk/lib/fdio/include/lib/fdio/unsafe.h#48)

<pre class="devsite-disable-click-to-copy">
<span class="typ">void</span> <b>fdio_unsafe_wait_begin</b>(<span class="typ">fdio_t *</span> io,
                            <span class="typ">uint32_t</span> events,
                            <span class="typ">zx_handle_t *</span> handle_out,
                            <span class="typ">zx_signals_t *</span> signals_out);
</pre>

This given a fdio_t, and a bitmask of posix-style events (EPOLLIN, EPOLLOUT, EPOLLERR), this
returns a handle that may be waited upon and a  bitmask of which signals to wait on for the
desired events.

The handle belongs to the fdio_t, is not duplicated, and may be closed() by the fdio library but
MUST NOT be closed by the caller.

If waiting is not supported by this fdio_t, the returned handle is ZX_HANDLE_INVALID.

This function is only safe to call on a fdio_t you hold a reference to.  It is not required that
`fdio_unsafe_wait_end()` be called after this.


## fdio_unsafe_wait_end(…) {:#fdio_unsafe_wait_end}

[Declaration source code](https://fuchsia.googlesource.com/fuchsia/+/refs/heads/main/sdk/lib/fdio/include/lib/fdio/unsafe.h#55)

<pre class="devsite-disable-click-to-copy">
<span class="typ">void</span> <b>fdio_unsafe_wait_end</b>(<span class="typ">fdio_t *</span> io,
                          <span class="typ">zx_signals_t</span> signals,
                          <span class="typ">uint32_t *</span> events_out);
</pre>

This given a set of signals observed on a handle obtained from fdio_unsafe_wait_begin() returns a
set of posix-style events that are indicated.

This function is only safe to call on a fdio_t you hold a reference to.