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//! A raw shared memory pool handler.
//!
//! This is intended as a safe building block for higher level shared memory pool abstractions and is not
//! encouraged for most library users.
use rustix::{
io::Errno,
shm::{Mode, ShmOFlags},
};
use std::{
fs::File,
io,
os::unix::prelude::{AsFd, OwnedFd},
sync::Arc,
time::{SystemTime, UNIX_EPOCH},
};
use memmap2::MmapMut;
use wayland_client::{
backend::ObjectData,
protocol::{wl_buffer, wl_shm, wl_shm_pool},
Dispatch, Proxy, QueueHandle, WEnum,
};
use crate::globals::ProvidesBoundGlobal;
use super::CreatePoolError;
/// A raw handler for file backed shared memory pools.
///
/// This type of pool will create the SHM memory pool and provide a way to resize the pool.
///
/// This pool does not release buffers. If you need this, use one of the higher level pools.
#[derive(Debug)]
pub struct RawPool {
pool: wl_shm_pool::WlShmPool,
len: usize,
mem_file: File,
mmap: MmapMut,
}
impl RawPool {
pub fn new(
len: usize,
shm: &impl ProvidesBoundGlobal<wl_shm::WlShm, 1>,
) -> Result<RawPool, CreatePoolError> {
let shm = shm.bound_global()?;
let shm_fd = RawPool::create_shm_fd()?;
let mem_file = File::from(shm_fd);
mem_file.set_len(len as u64)?;
let pool = shm
.send_constructor(
wl_shm::Request::CreatePool { fd: mem_file.as_fd(), size: len as i32 },
Arc::new(ShmPoolData),
)
.unwrap_or_else(|_| Proxy::inert(shm.backend().clone()));
let mmap = unsafe { MmapMut::map_mut(&mem_file)? };
Ok(RawPool { pool, len, mem_file, mmap })
}
/// Resizes the memory pool, notifying the server the pool has changed in size.
///
/// The wl_shm protocol only allows the pool to be made bigger. If the new size is smaller than the
/// current size of the pool, this function will do nothing.
pub fn resize(&mut self, size: usize) -> io::Result<()> {
if size > self.len {
self.len = size;
self.mem_file.set_len(size as u64)?;
self.pool.resize(size as i32);
self.mmap = unsafe { MmapMut::map_mut(&self.mem_file) }?;
}
Ok(())
}
/// Returns a reference to the underlying shared memory file using the memmap2 crate.
pub fn mmap(&mut self) -> &mut MmapMut {
&mut self.mmap
}
/// Returns the size of the mempool
#[allow(clippy::len_without_is_empty)]
pub fn len(&self) -> usize {
self.len
}
/// Create a new buffer to this pool.
///
/// ## Parameters
/// - `offset`: the offset (in bytes) from the beginning of the pool at which this buffer starts.
/// - `width` and `height`: the width and height of the buffer in pixels.
/// - `stride`: distance (in bytes) between the beginning of a row and the next one.
/// - `format`: the encoding format of the pixels.
///
/// The encoding format of the pixels must be supported by the compositor or else a protocol error is
/// risen. You can ensure the format is supported by listening to [`Shm::formats`](crate::shm::Shm::formats).
///
/// Note this function only creates the wl_buffer object, you will need to write to the pixels using the
/// [`io::Write`] implementation or [`RawPool::mmap`].
#[allow(clippy::too_many_arguments)]
pub fn create_buffer<D, U>(
&mut self,
offset: i32,
width: i32,
height: i32,
stride: i32,
format: wl_shm::Format,
udata: U,
qh: &QueueHandle<D>,
) -> wl_buffer::WlBuffer
where
D: Dispatch<wl_buffer::WlBuffer, U> + 'static,
U: Send + Sync + 'static,
{
self.pool.create_buffer(offset, width, height, stride, format, qh, udata)
}
/// Create a new buffer to this pool.
///
/// This is identical to [Self::create_buffer], but allows using a custom [ObjectData]
/// implementation instead of relying on the [Dispatch] interface.
#[allow(clippy::too_many_arguments)]
pub fn create_buffer_raw(
&mut self,
offset: i32,
width: i32,
height: i32,
stride: i32,
format: wl_shm::Format,
data: Arc<dyn ObjectData + 'static>,
) -> wl_buffer::WlBuffer {
self.pool
.send_constructor(
wl_shm_pool::Request::CreateBuffer {
offset,
width,
height,
stride,
format: WEnum::Value(format),
},
data,
)
.unwrap_or_else(|_| Proxy::inert(self.pool.backend().clone()))
}
/// Returns the pool object used to communicate with the server.
pub fn pool(&self) -> &wl_shm_pool::WlShmPool {
&self.pool
}
}
impl io::Write for RawPool {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
io::Write::write(&mut self.mem_file, buf)
}
fn flush(&mut self) -> io::Result<()> {
io::Write::flush(&mut self.mem_file)
}
}
impl io::Seek for RawPool {
fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> {
io::Seek::seek(&mut self.mem_file, pos)
}
}
impl RawPool {
fn create_shm_fd() -> io::Result<OwnedFd> {
#[cfg(target_os = "linux")]
{
match RawPool::create_memfd() {
Ok(fd) => return Ok(fd),
// Not supported, use fallback.
Err(Errno::NOSYS) => (),
Err(err) => return Err(Into::<io::Error>::into(err)),
};
}
let time = SystemTime::now();
let mut mem_file_handle = format!(
"/smithay-client-toolkit-{}",
time.duration_since(UNIX_EPOCH).unwrap().subsec_nanos()
);
loop {
let flags = ShmOFlags::CREATE | ShmOFlags::EXCL | ShmOFlags::RDWR;
let mode = Mode::RUSR | Mode::WUSR;
match rustix::shm::shm_open(mem_file_handle.as_str(), flags, mode) {
Ok(fd) => match rustix::shm::shm_unlink(mem_file_handle.as_str()) {
Ok(_) => return Ok(fd),
Err(errno) => {
return Err(errno.into());
}
},
Err(Errno::EXIST) => {
// Change the handle if we happen to be duplicate.
let time = SystemTime::now();
mem_file_handle = format!(
"/smithay-client-toolkit-{}",
time.duration_since(UNIX_EPOCH).unwrap().subsec_nanos()
);
continue;
}
Err(Errno::INTR) => continue,
Err(err) => return Err(err.into()),
}
}
}
#[cfg(target_os = "linux")]
fn create_memfd() -> rustix::io::Result<OwnedFd> {
use std::ffi::CStr;
use rustix::fs::{MemfdFlags, SealFlags};
loop {
let name = CStr::from_bytes_with_nul(b"smithay-client-toolkit\0").unwrap();
let flags = MemfdFlags::ALLOW_SEALING | MemfdFlags::CLOEXEC;
match rustix::fs::memfd_create(name, flags) {
Ok(fd) => {
// We only need to seal for the purposes of optimization, ignore the errors.
let _ = rustix::fs::fcntl_add_seals(&fd, SealFlags::SHRINK | SealFlags::SEAL);
return Ok(fd);
}
Err(Errno::INTR) => continue,
Err(err) => return Err(err),
}
}
}
}
impl Drop for RawPool {
fn drop(&mut self) {
self.pool.destroy();
}
}
#[derive(Debug)]
struct ShmPoolData;
impl ObjectData for ShmPoolData {
fn event(
self: Arc<Self>,
_: &wayland_client::backend::Backend,
_: wayland_client::backend::protocol::Message<wayland_client::backend::ObjectId, OwnedFd>,
) -> Option<Arc<(dyn ObjectData + 'static)>> {
unreachable!("wl_shm_pool has no events")
}
fn destroyed(&self, _: wayland_client::backend::ObjectId) {}
}