1use std::marker::PhantomData;
2use std::ops::Range;
3
4pub struct Buffer<T> {
6 pub raw: wgpu::Buffer,
7
8 label: &'static str,
9 size: u64,
10 usage: wgpu::BufferUsages,
11 type_: PhantomData<T>,
12}
13
14impl<T: bytemuck::Pod> Buffer<T> {
15 pub fn new(
16 device: &wgpu::Device,
17 label: &'static str,
18 amount: usize,
19 usage: wgpu::BufferUsages,
20 ) -> Self {
21 let size = next_copy_size::<T>(amount);
22
23 let raw = device.create_buffer(&wgpu::BufferDescriptor {
24 label: Some(label),
25 size,
26 usage,
27 mapped_at_creation: false,
28 });
29
30 Self {
31 label,
32 size,
33 usage,
34 raw,
35 type_: PhantomData,
36 }
37 }
38
39 pub fn expand_to_fit_new_size(&mut self, device: &wgpu::Device, new_count: usize) -> bool {
41 let new_size = (std::mem::size_of::<T>() * new_count) as u64;
42
43 if self.size < new_size {
44 self.raw = device.create_buffer(&wgpu::BufferDescriptor {
45 label: Some(self.label),
46 size: new_size,
47 usage: self.usage,
48 mapped_at_creation: false,
49 });
50
51 self.size = new_size;
52
53 true
54 } else {
55 false
56 }
57 }
58
59 pub fn write(&mut self, queue: &wgpu::Queue, offset: usize, contents: &[T]) -> usize {
61 let offset = offset as u64 * std::mem::size_of::<T>() as u64;
62
63 let bytes: &[u8] = bytemuck::cast_slice(contents);
64 queue.write_buffer(&self.raw, offset, bytes);
65
66 bytes.len()
67 }
68
69 pub fn slice(&self, range: Range<usize>) -> wgpu::BufferSlice<'_> {
70 self.raw.slice(
71 range.start as u64 * std::mem::size_of::<T>() as u64
72 ..range.end as u64 * std::mem::size_of::<T>() as u64,
73 )
74 }
75
76 pub fn label(&self) -> &'static str {
77 self.label
78 }
79}
80
81pub fn next_copy_size<T>(amount: usize) -> u64 {
82 let align_mask = wgpu::COPY_BUFFER_ALIGNMENT - 1;
83
84 (((std::mem::size_of::<T>() * amount).next_power_of_two() as u64 + align_mask) & !align_mask)
85 .max(wgpu::COPY_BUFFER_ALIGNMENT)
86}