1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
use std::{marker::PhantomData, num::NonZeroU64};

use crate::{
    render_resource::Buffer,
    renderer::{RenderDevice, RenderQueue},
};
use encase::{
    internal::{AlignmentValue, BufferMut, WriteInto},
    DynamicUniformBuffer as DynamicUniformBufferWrapper, ShaderType,
    UniformBuffer as UniformBufferWrapper,
};
use wgpu::{
    util::BufferInitDescriptor, BindingResource, BufferBinding, BufferDescriptor, BufferUsages,
};

use super::IntoBinding;

/// Stores data to be transferred to the GPU and made accessible to shaders as a uniform buffer.
///
/// Uniform buffers are available to shaders on a read-only basis. Uniform buffers are commonly used to make available to shaders
/// parameters that are constant during shader execution, and are best used for data that is relatively small in size as they are
/// only guaranteed to support up to 16kB per binding.
///
/// The contained data is stored in system RAM. [`write_buffer`](UniformBuffer::write_buffer) queues
/// copying of the data from system RAM to VRAM. Data in uniform buffers must follow [std140 alignment/padding requirements],
/// which is automatically enforced by this structure. Per the WGPU spec, uniform buffers cannot store runtime-sized array
/// (vectors), or structures with fields that are vectors.
///
/// Other options for storing GPU-accessible data are:
/// * [`StorageBuffer`](crate::render_resource::StorageBuffer)
/// * [`DynamicStorageBuffer`](crate::render_resource::DynamicStorageBuffer)
/// * [`DynamicUniformBuffer`]
/// * [`GpuArrayBuffer`](crate::render_resource::GpuArrayBuffer)
/// * [`RawBufferVec`](crate::render_resource::RawBufferVec)
/// * [`BufferVec`](crate::render_resource::BufferVec)
/// * [`Texture`](crate::render_resource::Texture)
///
/// [std140 alignment/padding requirements]: https://www.w3.org/TR/WGSL/#address-spaces-uniform
pub struct UniformBuffer<T: ShaderType> {
    value: T,
    scratch: UniformBufferWrapper<Vec<u8>>,
    buffer: Option<Buffer>,
    label: Option<String>,
    changed: bool,
    buffer_usage: BufferUsages,
}

impl<T: ShaderType> From<T> for UniformBuffer<T> {
    fn from(value: T) -> Self {
        Self {
            value,
            scratch: UniformBufferWrapper::new(Vec::new()),
            buffer: None,
            label: None,
            changed: false,
            buffer_usage: BufferUsages::COPY_DST | BufferUsages::UNIFORM,
        }
    }
}

impl<T: ShaderType + Default> Default for UniformBuffer<T> {
    fn default() -> Self {
        Self {
            value: T::default(),
            scratch: UniformBufferWrapper::new(Vec::new()),
            buffer: None,
            label: None,
            changed: false,
            buffer_usage: BufferUsages::COPY_DST | BufferUsages::UNIFORM,
        }
    }
}

impl<T: ShaderType + WriteInto> UniformBuffer<T> {
    #[inline]
    pub fn buffer(&self) -> Option<&Buffer> {
        self.buffer.as_ref()
    }

    #[inline]
    pub fn binding(&self) -> Option<BindingResource> {
        Some(BindingResource::Buffer(
            self.buffer()?.as_entire_buffer_binding(),
        ))
    }

    /// Set the data the buffer stores.
    pub fn set(&mut self, value: T) {
        self.value = value;
    }

    pub fn get(&self) -> &T {
        &self.value
    }

    pub fn get_mut(&mut self) -> &mut T {
        &mut self.value
    }

    pub fn set_label(&mut self, label: Option<&str>) {
        let label = label.map(str::to_string);

        if label != self.label {
            self.changed = true;
        }

        self.label = label;
    }

    pub fn get_label(&self) -> Option<&str> {
        self.label.as_deref()
    }

    /// Add more [`BufferUsages`] to the buffer.
    ///
    /// This method only allows addition of flags to the default usage flags.
    ///
    /// The default values for buffer usage are `BufferUsages::COPY_DST` and `BufferUsages::UNIFORM`.
    pub fn add_usages(&mut self, usage: BufferUsages) {
        self.buffer_usage |= usage;
        self.changed = true;
    }

    /// Queues writing of data from system RAM to VRAM using the [`RenderDevice`]
    /// and the provided [`RenderQueue`], if a GPU-side backing buffer already exists.
    ///
    /// If a GPU-side buffer does not already exist for this data, such a buffer is initialized with currently
    /// available data.
    pub fn write_buffer(&mut self, device: &RenderDevice, queue: &RenderQueue) {
        self.scratch.write(&self.value).unwrap();

        if self.changed || self.buffer.is_none() {
            self.buffer = Some(device.create_buffer_with_data(&BufferInitDescriptor {
                label: self.label.as_deref(),
                usage: self.buffer_usage,
                contents: self.scratch.as_ref(),
            }));
            self.changed = false;
        } else if let Some(buffer) = &self.buffer {
            queue.write_buffer(buffer, 0, self.scratch.as_ref());
        }
    }
}

impl<'a, T: ShaderType + WriteInto> IntoBinding<'a> for &'a UniformBuffer<T> {
    #[inline]
    fn into_binding(self) -> BindingResource<'a> {
        self.buffer()
            .expect("Failed to get buffer")
            .as_entire_buffer_binding()
            .into_binding()
    }
}

/// Stores data to be transferred to the GPU and made accessible to shaders as a dynamic uniform buffer.
///
/// Dynamic uniform buffers are available to shaders on a read-only basis. Dynamic uniform buffers are commonly used to make
/// available to shaders runtime-sized arrays of parameters that are otherwise constant during shader execution, and are best
/// suited to data that is relatively small in size as they are only guaranteed to support up to 16kB per binding.
///
/// The contained data is stored in system RAM. [`write_buffer`](DynamicUniformBuffer::write_buffer) queues
/// copying of the data from system RAM to VRAM. Data in uniform buffers must follow [std140 alignment/padding requirements],
/// which is automatically enforced by this structure. Per the WGPU spec, uniform buffers cannot store runtime-sized array
/// (vectors), or structures with fields that are vectors.
///
/// Other options for storing GPU-accessible data are:
/// * [`StorageBuffer`](crate::render_resource::StorageBuffer)
/// * [`DynamicStorageBuffer`](crate::render_resource::DynamicStorageBuffer)
/// * [`UniformBuffer`]
/// * [`DynamicUniformBuffer`]
/// * [`GpuArrayBuffer`](crate::render_resource::GpuArrayBuffer)
/// * [`RawBufferVec`](crate::render_resource::RawBufferVec)
/// * [`BufferVec`](crate::render_resource::BufferVec)
/// * [`Texture`](crate::render_resource::Texture)
///
/// [std140 alignment/padding requirements]: https://www.w3.org/TR/WGSL/#address-spaces-uniform
pub struct DynamicUniformBuffer<T: ShaderType> {
    scratch: DynamicUniformBufferWrapper<Vec<u8>>,
    buffer: Option<Buffer>,
    label: Option<String>,
    changed: bool,
    buffer_usage: BufferUsages,
    _marker: PhantomData<fn() -> T>,
}

impl<T: ShaderType> Default for DynamicUniformBuffer<T> {
    fn default() -> Self {
        Self {
            scratch: DynamicUniformBufferWrapper::new(Vec::new()),
            buffer: None,
            label: None,
            changed: false,
            buffer_usage: BufferUsages::COPY_DST | BufferUsages::UNIFORM,
            _marker: PhantomData,
        }
    }
}

impl<T: ShaderType + WriteInto> DynamicUniformBuffer<T> {
    pub fn new_with_alignment(alignment: u64) -> Self {
        Self {
            scratch: DynamicUniformBufferWrapper::new_with_alignment(Vec::new(), alignment),
            buffer: None,
            label: None,
            changed: false,
            buffer_usage: BufferUsages::COPY_DST | BufferUsages::UNIFORM,
            _marker: PhantomData,
        }
    }

    #[inline]
    pub fn buffer(&self) -> Option<&Buffer> {
        self.buffer.as_ref()
    }

    #[inline]
    pub fn binding(&self) -> Option<BindingResource> {
        Some(BindingResource::Buffer(BufferBinding {
            buffer: self.buffer()?,
            offset: 0,
            size: Some(T::min_size()),
        }))
    }

    #[inline]
    pub fn is_empty(&self) -> bool {
        self.scratch.as_ref().is_empty()
    }

    /// Push data into the `DynamicUniformBuffer`'s internal vector (residing on system RAM).
    #[inline]
    pub fn push(&mut self, value: &T) -> u32 {
        self.scratch.write(value).unwrap() as u32
    }

    pub fn set_label(&mut self, label: Option<&str>) {
        let label = label.map(str::to_string);

        if label != self.label {
            self.changed = true;
        }

        self.label = label;
    }

    pub fn get_label(&self) -> Option<&str> {
        self.label.as_deref()
    }

    /// Add more [`BufferUsages`] to the buffer.
    ///
    /// This method only allows addition of flags to the default usage flags.
    ///
    /// The default values for buffer usage are `BufferUsages::COPY_DST` and `BufferUsages::UNIFORM`.
    pub fn add_usages(&mut self, usage: BufferUsages) {
        self.buffer_usage |= usage;
        self.changed = true;
    }

    /// Creates a writer that can be used to directly write elements into the target buffer.
    ///
    /// This method uses less memory and performs fewer memory copies using over [`push`] and [`write_buffer`].
    ///
    /// `max_count` *must* be greater than or equal to the number of elements that are to be written to the buffer, or
    /// the writer will panic while writing.  Dropping the writer will schedule the buffer write into the provided
    /// [`RenderQueue`].
    ///
    /// If there is no GPU-side buffer allocated to hold the data currently stored, or if a GPU-side buffer previously
    /// allocated does not have enough capacity to hold `max_count` elements, a new GPU-side buffer is created.
    ///
    /// Returns `None` if there is no allocated GPU-side buffer, and `max_count` is 0.
    ///
    /// [`push`]: Self::push
    /// [`write_buffer`]: Self::write_buffer
    #[inline]
    pub fn get_writer<'a>(
        &'a mut self,
        max_count: usize,
        device: &RenderDevice,
        queue: &'a RenderQueue,
    ) -> Option<DynamicUniformBufferWriter<'a, T>> {
        let alignment = if cfg!(feature = "ios_simulator") {
            // On iOS simulator on silicon macs, metal validation check that the host OS alignment
            // is respected, but the device reports the correct value for iOS, which is smaller.
            // Use the larger value.
            // See https://github.com/bevyengine/bevy/pull/10178 - remove if it's not needed anymore.
            AlignmentValue::new(256)
        } else {
            AlignmentValue::new(device.limits().min_uniform_buffer_offset_alignment as u64)
        };

        let mut capacity = self.buffer.as_deref().map(wgpu::Buffer::size).unwrap_or(0);
        let size = alignment
            .round_up(T::min_size().get())
            .checked_mul(max_count as u64)
            .unwrap();

        if capacity < size || (self.changed && size > 0) {
            let buffer = device.create_buffer(&BufferDescriptor {
                label: self.label.as_deref(),
                usage: self.buffer_usage,
                size,
                mapped_at_creation: false,
            });
            capacity = buffer.size();
            self.buffer = Some(buffer);
            self.changed = false;
        }

        if let Some(buffer) = self.buffer.as_deref() {
            let buffer_view = queue
                .write_buffer_with(buffer, 0, NonZeroU64::new(buffer.size())?)
                .unwrap();
            Some(DynamicUniformBufferWriter {
                buffer: encase::DynamicUniformBuffer::new_with_alignment(
                    QueueWriteBufferViewWrapper {
                        capacity: capacity as usize,
                        buffer_view,
                    },
                    alignment.get(),
                ),
                _marker: PhantomData,
            })
        } else {
            None
        }
    }

    /// Queues writing of data from system RAM to VRAM using the [`RenderDevice`]
    /// and the provided [`RenderQueue`].
    ///
    /// If there is no GPU-side buffer allocated to hold the data currently stored, or if a GPU-side buffer previously
    /// allocated does not have enough capacity, a new GPU-side buffer is created.
    #[inline]
    pub fn write_buffer(&mut self, device: &RenderDevice, queue: &RenderQueue) {
        let capacity = self.buffer.as_deref().map(wgpu::Buffer::size).unwrap_or(0);
        let size = self.scratch.as_ref().len() as u64;

        if capacity < size || (self.changed && size > 0) {
            self.buffer = Some(device.create_buffer_with_data(&BufferInitDescriptor {
                label: self.label.as_deref(),
                usage: self.buffer_usage,
                contents: self.scratch.as_ref(),
            }));
            self.changed = false;
        } else if let Some(buffer) = &self.buffer {
            queue.write_buffer(buffer, 0, self.scratch.as_ref());
        }
    }

    #[inline]
    pub fn clear(&mut self) {
        self.scratch.as_mut().clear();
        self.scratch.set_offset(0);
    }
}

/// A writer that can be used to directly write elements into the target buffer.
///
/// For more information, see [`DynamicUniformBuffer::get_writer`].
pub struct DynamicUniformBufferWriter<'a, T> {
    buffer: encase::DynamicUniformBuffer<QueueWriteBufferViewWrapper<'a>>,
    _marker: PhantomData<fn() -> T>,
}

impl<'a, T: ShaderType + WriteInto> DynamicUniformBufferWriter<'a, T> {
    pub fn write(&mut self, value: &T) -> u32 {
        self.buffer.write(value).unwrap() as u32
    }
}

/// A wrapper to work around the orphan rule so that [`wgpu::QueueWriteBufferView`] can  implement
/// [`BufferMut`].
struct QueueWriteBufferViewWrapper<'a> {
    buffer_view: wgpu::QueueWriteBufferView<'a>,
    // Must be kept separately and cannot be retrieved from buffer_view, as the read-only access will
    // invoke a panic.
    capacity: usize,
}

impl<'a> BufferMut for QueueWriteBufferViewWrapper<'a> {
    #[inline]
    fn capacity(&self) -> usize {
        self.capacity
    }

    #[inline]
    fn write<const N: usize>(&mut self, offset: usize, val: &[u8; N]) {
        self.buffer_view.write(offset, val);
    }

    #[inline]
    fn write_slice(&mut self, offset: usize, val: &[u8]) {
        self.buffer_view.write_slice(offset, val);
    }
}

impl<'a, T: ShaderType + WriteInto> IntoBinding<'a> for &'a DynamicUniformBuffer<T> {
    #[inline]
    fn into_binding(self) -> BindingResource<'a> {
        self.binding().unwrap()
    }
}