wgpu/api/queue.rs
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use alloc::boxed::Box;
use core::ops::{Deref, DerefMut};
use crate::*;
/// Handle to a command queue on a device.
///
/// A `Queue` executes recorded [`CommandBuffer`] objects and provides convenience methods
/// for writing to [buffers](Queue::write_buffer) and [textures](Queue::write_texture).
/// It can be created along with a [`Device`] by calling [`Adapter::request_device`].
///
/// Corresponds to [WebGPU `GPUQueue`](https://gpuweb.github.io/gpuweb/#gpu-queue).
#[derive(Debug, Clone)]
pub struct Queue {
pub(crate) inner: dispatch::DispatchQueue,
}
#[cfg(send_sync)]
static_assertions::assert_impl_all!(Queue: Send, Sync);
crate::cmp::impl_eq_ord_hash_proxy!(Queue => .inner);
/// Identifier for a particular call to [`Queue::submit`]. Can be used
/// as part of an argument to [`Device::poll`] to block for a particular
/// submission to finish.
///
/// This type is unique to the Rust API of `wgpu`.
/// There is no analogue in the WebGPU specification.
#[derive(Debug, Clone)]
pub struct SubmissionIndex {
#[cfg_attr(not(wgpu_core), expect(dead_code))]
pub(crate) index: u64,
}
#[cfg(send_sync)]
static_assertions::assert_impl_all!(SubmissionIndex: Send, Sync);
pub use wgt::PollType as MaintainBase;
/// Passed to [`Device::poll`] to control how and if it should block.
pub type PollType = wgt::PollType<SubmissionIndex>;
#[cfg(send_sync)]
static_assertions::assert_impl_all!(PollType: Send, Sync);
/// A write-only view into a staging buffer.
///
/// Reading into this buffer won't yield the contents of the buffer from the
/// GPU and is likely to be slow. Because of this, although [`AsMut`] is
/// implemented for this type, [`AsRef`] is not.
pub struct QueueWriteBufferView<'a> {
queue: &'a Queue,
buffer: &'a Buffer,
offset: BufferAddress,
inner: dispatch::DispatchQueueWriteBuffer,
}
#[cfg(send_sync)]
static_assertions::assert_impl_all!(QueueWriteBufferView<'_>: Send, Sync);
impl Deref for QueueWriteBufferView<'_> {
type Target = [u8];
fn deref(&self) -> &Self::Target {
log::warn!("Reading from a QueueWriteBufferView won't yield the contents of the buffer and may be slow.");
self.inner.slice()
}
}
impl DerefMut for QueueWriteBufferView<'_> {
fn deref_mut(&mut self) -> &mut Self::Target {
self.inner.slice_mut()
}
}
impl AsMut<[u8]> for QueueWriteBufferView<'_> {
fn as_mut(&mut self) -> &mut [u8] {
self.inner.slice_mut()
}
}
impl Drop for QueueWriteBufferView<'_> {
fn drop(&mut self) {
self.queue
.inner
.write_staging_buffer(&self.buffer.inner, self.offset, &self.inner);
}
}
impl Queue {
#[cfg(custom)]
/// Creates Queue from custom implementation
pub fn from_custom<T: custom::QueueInterface>(queue: T) -> Self {
Self {
inner: dispatch::DispatchQueue::custom(queue),
}
}
/// Copies the bytes of `data` into `buffer` starting at `offset`.
///
/// The data must be written fully in-bounds, that is, `offset + data.len() <= buffer.len()`.
///
/// # Performance considerations
///
/// * Calls to `write_buffer()` do *not* submit the transfer to the GPU
/// immediately. They begin GPU execution only on the next call to
/// [`Queue::submit()`], just before the explicitly submitted commands.
/// To get a set of scheduled transfers started immediately,
/// it's fine to call `submit` with no command buffers at all:
///
/// ```no_run
/// # let queue: wgpu::Queue = todo!();
/// # let buffer: wgpu::Buffer = todo!();
/// # let data = [0u8];
/// queue.write_buffer(&buffer, 0, &data);
/// queue.submit([]);
/// ```
///
/// However, `data` will be immediately copied into staging memory, so the
/// caller may discard it any time after this call completes.
///
/// * Consider using [`Queue::write_buffer_with()`] instead.
/// That method allows you to prepare your data directly within the staging
/// memory, rather than first placing it in a separate `[u8]` to be copied.
/// That is, `queue.write_buffer(b, offset, data)` is approximately equivalent
/// to `queue.write_buffer_with(b, offset, data.len()).copy_from_slice(data)`,
/// so use `write_buffer_with()` if you can do something smarter than that
/// [`copy_from_slice()`](slice::copy_from_slice). However, for small values
/// (e.g. a typical uniform buffer whose contents come from a `struct`),
/// there will likely be no difference, since the compiler will be able to
/// optimize out unnecessary copies regardless.
///
/// * Currently on native platforms, for both of these methods, the staging
/// memory will be a new allocation. This will then be released after the
/// next submission finishes. To entirely avoid short-lived allocations, you might
/// be able to use [`StagingBelt`](crate::util::StagingBelt),
/// or buffers you explicitly create, map, and unmap yourself.
pub fn write_buffer(&self, buffer: &Buffer, offset: BufferAddress, data: &[u8]) {
self.inner.write_buffer(&buffer.inner, offset, data);
}
/// Prepares to write data to a buffer via a mapped staging buffer.
///
/// This operation allocates a temporary buffer and then returns a
/// [`QueueWriteBufferView`], which
///
/// * dereferences to a `[u8]` of length `size`, and
/// * when dropped, schedules a copy of its contents into `buffer` at `offset`.
///
/// Therefore, this obtains the same result as [`Queue::write_buffer()`], but may
/// allow you to skip one allocation and one copy of your data, if you are able to
/// assemble your data directly into the returned [`QueueWriteBufferView`] instead of
/// into a separate allocation like a [`Vec`](alloc::vec::Vec) first.
///
/// The data must be written fully in-bounds, that is, `offset + size <= buffer.len()`.
///
/// # Performance considerations
///
/// * For small data not separately heap-allocated, there is no advantage of this
/// over [`Queue::write_buffer()`].
///
/// * Reading from the returned view may be slow, and will not yield the current
/// contents of `buffer`. You should treat it as “write-only”.
///
/// * Dropping the [`QueueWriteBufferView`] does *not* submit the
/// transfer to the GPU immediately. The transfer begins only on the next
/// call to [`Queue::submit()`] after the view is dropped, just before the
/// explicitly submitted commands. To get a set of scheduled transfers started
/// immediately, it's fine to call `queue.submit([])` with no command buffers at all.
///
/// * Currently on native platforms, the staging memory will be a new allocation, which will
/// then be released after the next submission finishes. To entirely avoid short-lived
/// allocations, you might be able to use [`StagingBelt`](crate::util::StagingBelt),
/// or buffers you explicitly create, map, and unmap yourself.
#[must_use]
pub fn write_buffer_with<'a>(
&'a self,
buffer: &'a Buffer,
offset: BufferAddress,
size: BufferSize,
) -> Option<QueueWriteBufferView<'a>> {
profiling::scope!("Queue::write_buffer_with");
self.inner
.validate_write_buffer(&buffer.inner, offset, size)?;
let staging_buffer = self.inner.create_staging_buffer(size)?;
Some(QueueWriteBufferView {
queue: self,
buffer,
offset,
inner: staging_buffer,
})
}
/// Copies the bytes of `data` into into a texture.
///
/// * `data` contains the texels to be written, which must be in
/// [the same format as the texture](TextureFormat).
/// * `data_layout` describes the memory layout of `data`, which does not necessarily
/// have to have tightly packed rows.
/// * `texture` specifies the texture to write into, and the location within the
/// texture (coordinate offset, mip level) that will be overwritten.
/// * `size` is the size, in texels, of the region to be written.
///
/// This method fails if `size` overruns the size of `texture`, or if `data` is too short.
///
/// # Performance considerations
///
/// This operation has the same performance considerations as [`Queue::write_buffer()`];
/// see its documentation for details.
///
/// However, since there is no “mapped texture” like a mapped buffer,
/// alternate techniques for writing to textures will generally consist of first copying
/// the data to a buffer, then using [`CommandEncoder::copy_buffer_to_texture()`], or in
/// some cases a compute shader, to copy texels from that buffer to the texture.
pub fn write_texture(
&self,
texture: TexelCopyTextureInfo<'_>,
data: &[u8],
data_layout: TexelCopyBufferLayout,
size: Extent3d,
) {
self.inner.write_texture(texture, data, data_layout, size);
}
/// Schedule a copy of data from `image` into `texture`.
#[cfg(any(webgpu, webgl))]
pub fn copy_external_image_to_texture(
&self,
source: &wgt::CopyExternalImageSourceInfo,
dest: wgt::CopyExternalImageDestInfo<&api::Texture>,
size: Extent3d,
) {
self.inner
.copy_external_image_to_texture(source, dest, size);
}
/// Submits a series of finished command buffers for execution.
pub fn submit<I: IntoIterator<Item = CommandBuffer>>(
&self,
command_buffers: I,
) -> SubmissionIndex {
let mut command_buffers = command_buffers.into_iter().map(|comb| comb.buffer);
let index = self.inner.submit(&mut command_buffers);
SubmissionIndex { index }
}
/// Gets the amount of nanoseconds each tick of a timestamp query represents.
///
/// Returns zero if timestamp queries are unsupported.
///
/// Timestamp values are represented in nanosecond values on WebGPU, see `<https://gpuweb.github.io/gpuweb/#timestamp>`
/// Therefore, this is always 1.0 on the web, but on wgpu-core a manual conversion is required.
pub fn get_timestamp_period(&self) -> f32 {
self.inner.get_timestamp_period()
}
/// Registers a callback when the previous call to submit finishes running on the gpu. This callback
/// being called implies that all mapped buffer callbacks which were registered before this call will
/// have been called.
///
/// For the callback to complete, either `queue.submit(..)`, `instance.poll_all(..)`, or `device.poll(..)`
/// must be called elsewhere in the runtime, possibly integrated into an event loop or run on a separate thread.
///
/// The callback will be called on the thread that first calls the above functions after the gpu work
/// has completed. There are no restrictions on the code you can run in the callback, however on native the
/// call to the function will not complete until the callback returns, so prefer keeping callbacks short
/// and used to set flags, send messages, etc.
pub fn on_submitted_work_done(&self, callback: impl FnOnce() + Send + 'static) {
self.inner.on_submitted_work_done(Box::new(callback));
}
/// Returns the inner hal Queue using a callback. The hal queue will be `None` if the
/// backend type argument does not match with this wgpu Queue
///
/// # Safety
///
/// - The raw handle obtained from the hal Queue must not be manually destroyed
#[cfg(wgpu_core)]
pub unsafe fn as_hal<A: wgc::hal_api::HalApi, F: FnOnce(Option<&A::Queue>) -> R, R>(
&self,
hal_queue_callback: F,
) -> R {
if let Some(core_queue) = self.inner.as_core_opt() {
unsafe {
core_queue
.context
.queue_as_hal::<A, F, R>(core_queue, hal_queue_callback)
}
} else {
hal_queue_callback(None)
}
}
}