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//! Graphics buffers. //! //! A GPU buffer is a typed continuous region of data. It has a size and can hold several elements. //! //! Once the buffer is created, you can perform several operations on it: //! //! - Writing to it. //! - Reading from it. //! - Passing it around as uniforms. //! - Etc. //! //! # Parametricity //! //! The [`Buffer`] type is parametric over the backend type and item type. For the backend type, //! the [`backend::buffer::Buffer`] trait must be implemented to be able to use it with the buffe. //! //! # Buffer creation, reading, writing and getting information //! //! Buffers are created with the [`Buffer::new`], [`Buffer::from_vec`] and [`Buffer::repeat`] //! methods. All these methods are fallible — they might fail with [`BufferError`]. //! //! Once you have a [`Buffer`], you can read from it and write to it. //! Writing is done with [`Buffer::set`] — which allows to set a value at a given index in the //! buffer, [`Buffer::write_whole`] — which writes a whole slice to the buffer — and //! [`Buffer::clear`] — which sets the same value to all items in a buffer. Reading is performed //! with [`Buffer::at`] — which retrieves the item at a given index and [`Buffer::whole`] which //! retrieves the whole buffer by copying it to a `Vec<T>`. //! //! It’s possible to get data via several methods, such as [`Buffer::len`] to get the number of //! items in the buffer. //! //! # Buffer slicing //! //! Buffer slicing is the act of getting a [`BufferSlice`] out of a [`Buffer`]. That operation //! allows to _map_ a GPU region onto a CPU one and access the underlying data as a regular slice. //! Two methods exist to slice a buffer //! //! - Read-only: [`Buffer::slice`]. //! - Mutably: [`Buffer::slice_mut`]. //! //! Both methods take a mutable reference on a buffer because even in the read-only case, exclusive //! borrowing must be enforced. //! //! [`backend::buffer::Buffer`]: crate::backend::buffer::Buffer use crate::{ backend::buffer::{Buffer as BufferBackend, BufferSlice as BufferSliceBackend}, context::GraphicsContext, }; use std::{ error, fmt, marker::PhantomData, ops::{Deref, DerefMut}, }; /// A GPU buffer. /// /// # Parametricity /// /// - `B` is the backend type. It must implement [`backend::buffer::Buffer`]. /// -`T` is the type of stored items. No restriction are currently enforced on that type, besides /// the fact it must be [`Sized`]. /// /// [`backend::buffer::Buffer`]: crate::backend::buffer::Buffer #[derive(Debug)] pub struct Buffer<B, T> where B: ?Sized + BufferBackend<T>, T: Copy, { pub(crate) repr: B::BufferRepr, _t: PhantomData<T>, } impl<B, T> Buffer<B, T> where B: ?Sized + BufferBackend<T>, T: Copy, { /// Create a new buffer with a given length /// /// The buffer will be created on the GPU with a contiguous region large enough to fit `len` /// items. /// /// The stored item must be [`Default`], as this function will initialize the whole buffer /// with the default value. /// /// # Errors /// /// That function can fail creating the buffer for various reasons, in which case it returns /// `Err(BufferError::_)`. Feel free to read the documentation of [`BufferError`] for further /// information. /// /// # Notes /// /// You might be interested in the [`GraphicsContext::new_buffer`] function instead, which /// is the exact same function, but benefits from more type inference (based on `&mut C`). pub fn new<C>(ctx: &mut C, len: usize) -> Result<Self, BufferError> where C: GraphicsContext<Backend = B>, T: Default, { let repr = unsafe { ctx.backend().new_buffer(len)? }; Ok(Buffer { repr, _t: PhantomData, }) } /// Create a new buffer from a slice of items. /// /// The buffer will be created with a length equal to the length of the input size, and items /// will be copied from the slice inside the contiguous GPU region. /// /// # Errors /// /// That function can fail creating the buffer for various reasons, in which case it returns /// `Err(BufferError::_)`. Feel free to read the documentation of [`BufferError`] for further /// information. /// /// # Notes /// /// You might be interested in the [`GraphicsContext::new_buffer_from_vec`] function instead, /// which is the exact same function, but benefits from more type inference (based on `&mut C`). pub fn from_vec<C, X>(ctx: &mut C, vec: X) -> Result<Self, BufferError> where C: GraphicsContext<Backend = B>, X: Into<Vec<T>>, { let repr = unsafe { ctx.backend().from_vec(vec.into())? }; Ok(Buffer { repr, _t: PhantomData, }) } /// Create a new buffer by repeating `len` times a `value`. /// /// The buffer will be comprised of `len` items, all equal to `value`. /// /// # Errors /// /// That function can fail creating the buffer for various reasons, in which case it returns /// `Err(BufferError::_)`. Feel free to read the documentation of [`BufferError`] for further /// information. /// /// # Notes /// /// You might be interested in the [`GraphicsContext::new_buffer_repeating`] function instead, /// which is the exact same function, but benefits from more type inference (based on `&mut C`). pub fn repeat<C>(ctx: &mut C, len: usize, value: T) -> Result<Self, BufferError> where C: GraphicsContext<Backend = B>, { let repr = unsafe { ctx.backend().repeat(len, value)? }; Ok(Buffer { repr, _t: PhantomData, }) } /// Get the item at the given index. pub fn at(&self, i: usize) -> Option<T> { unsafe { B::at(&self.repr, i) } } /// Get the whole content of the buffer and store it inside a [`Vec`]. pub fn whole(&self) -> Vec<T> { unsafe { B::whole(&self.repr) } } /// Set a value `x` at index `i` in the buffer. /// /// # Errors /// /// That function returns [`BufferError::Overflow`] if `i` is bigger than the length of the /// buffer. Other errors are possible; please consider reading the documentation of /// [`BufferError`] for further information. pub fn set(&mut self, i: usize, x: T) -> Result<(), BufferError> { unsafe { B::set(&mut self.repr, i, x) } } /// Set the content of the buffer by using a slice that will be copied at the buffer’s memory /// location. /// /// # Errors /// /// [`BufferError::TooFewValues`] is returned if the input slice has less items than the buffer. /// /// [`BufferError::TooManyValues`] is returned if the input slice has more items than the buffer. pub fn write_whole(&mut self, values: &[T]) -> Result<(), BufferError> { unsafe { B::write_whole(&mut self.repr, values) } } /// Clear the content of the buffer by copying the same value everywhere. pub fn clear(&mut self, x: T) -> Result<(), BufferError> { unsafe { B::clear(&mut self.repr, x) } } /// Return the length of the buffer (i.e. the number of elements). #[inline(always)] pub fn len(&self) -> usize { unsafe { B::len(&self.repr) } } /// Check whether the buffer is empty (i.e. it has no elements). /// /// # Note /// /// Since right now, it is not possible to grow vectors, it is highly recommended not to create /// empty buffers. That function is there only for convenience and demonstration; you shouldn’t /// really have to use it. #[inline(always)] pub fn is_empty(&self) -> bool { self.len() == 0 } } impl<B, T> Buffer<B, T> where B: ?Sized + BufferSliceBackend<T>, T: Copy, { /// Create a new [`BufferSlice`] from a buffer, allowing to get `&[T]` out of it. /// /// # Errors /// /// That function might fail and return a [`BufferError::MapFailed`]. pub fn slice(&mut self) -> Result<BufferSlice<B, T>, BufferError> { unsafe { B::slice_buffer(&mut self.repr).map(|slice| BufferSlice { slice, _a: PhantomData, }) } } /// Create a new [`BufferSliceMut`] from a buffer, allowing to get `&mut [T]` out of it. /// /// # Errors /// /// That function might fail and return a [`BufferError::MapFailed`]. pub fn slice_mut(&mut self) -> Result<BufferSliceMut<B, T>, BufferError> { unsafe { B::slice_buffer_mut(&mut self.repr).map(|slice| BufferSliceMut { slice, _a: PhantomData, }) } } } /// Buffer errors. /// /// Please keep in mind that this `enum` is _non exhaustive_; you will not be able to exhaustively /// pattern-match against it. #[non_exhaustive] #[derive(Debug, Eq, PartialEq)] pub enum BufferError { /// Cannot create buffer. CannotCreate, /// Overflow when setting a value with a specific index. /// /// Contains the index and the size of the buffer. Overflow { /// Tried index. index: usize, /// Actuall buffer length. buffer_len: usize, }, /// Too few values were passed to fill a buffer. /// /// Contains the number of passed value and the size of the buffer. TooFewValues { /// Length of the provided data. provided_len: usize, /// Actual buffer length. buffer_len: usize, }, /// Too many values were passed to fill a buffer. /// /// Contains the number of passed value and the size of the buffer. TooManyValues { /// Length of the provided data. provided_len: usize, /// Actual buffer length. buffer_len: usize, }, /// Buffer mapping failed. MapFailed, } impl BufferError { /// Cannot create [`Buffer`]. pub fn cannot_create() -> Self { BufferError::CannotCreate } /// Overflow when setting a value with a specific index. pub fn overflow(index: usize, buffer_len: usize) -> Self { BufferError::Overflow { index, buffer_len } } /// Too few values were passed to fill a buffer. pub fn too_few_values(provided_len: usize, buffer_len: usize) -> Self { BufferError::TooFewValues { provided_len, buffer_len, } } /// Too many values were passed to fill a buffer. pub fn too_many_values(provided_len: usize, buffer_len: usize) -> Self { BufferError::TooManyValues { provided_len, buffer_len, } } /// Buffer mapping failed. pub fn map_failed() -> Self { BufferError::MapFailed } } impl fmt::Display for BufferError { fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> { match *self { BufferError::CannotCreate => f.write_str("cannot create buffer"), BufferError::Overflow { index, buffer_len } => write!( f, "buffer overflow (index = {}, size = {})", index, buffer_len ), BufferError::TooFewValues { provided_len, buffer_len, } => write!( f, "too few values passed to the buffer (nb = {}, size = {})", provided_len, buffer_len ), BufferError::TooManyValues { provided_len, buffer_len, } => write!( f, "too many values passed to the buffer (nb = {}, size = {})", provided_len, buffer_len ), BufferError::MapFailed => f.write_str("buffer mapping failed"), } } } impl error::Error for BufferError {} /// A buffer slice, allowing to get `&[T]`. #[derive(Debug)] pub struct BufferSlice<'a, B, T> where B: ?Sized + BufferSliceBackend<T>, T: Copy, { slice: B::SliceRepr, _a: PhantomData<&'a mut ()>, } impl<'a, B, T> Deref for BufferSlice<'a, B, T> where B: ?Sized + BufferSliceBackend<T>, T: Copy, { type Target = [T]; fn deref(&self) -> &Self::Target { self.slice.deref() } } /// A buffer mutable slice, allowing to get `&mut [T]`. #[derive(Debug)] pub struct BufferSliceMut<'a, B, T> where B: ?Sized + BufferSliceBackend<T>, T: Copy, { slice: B::SliceMutRepr, _a: PhantomData<&'a mut ()>, } impl<'a, B, T> Deref for BufferSliceMut<'a, B, T> where B: ?Sized + BufferSliceBackend<T>, T: Copy, { type Target = [T]; fn deref(&self) -> &Self::Target { self.slice.deref() } } impl<'a, B, T> DerefMut for BufferSliceMut<'a, B, T> where B: ?Sized + BufferSliceBackend<T>, T: Copy, { fn deref_mut(&mut self) -> &mut Self::Target { self.slice.deref_mut() } }