Add support for presser

.github/workflows/ci.yml

@@ -9,9 +9,9 @@ jobs:
       matrix:
         include:
         - os: ubuntu-latest
-          features: vulkan,visualizer
+          features: vulkan,visualizer,presser
         - os: windows-latest
-          features: vulkan,visualizer,d3d12,public-winapi
+          features: vulkan,visualizer,d3d12,public-winapi,presser
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v3
@@ -31,9 +31,9 @@ jobs:
       matrix:
         include:
         - os: ubuntu-latest
-          features: vulkan,visualizer
+          features: vulkan,visualizer,presser
         - os: windows-latest
-          features: vulkan,visualizer,d3d12,public-winapi
+          features: vulkan,visualizer,d3d12,public-winapi,presser
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v3
@@ -75,9 +75,9 @@ jobs:
       matrix:
         include:
         - os: ubuntu-latest
-          features: vulkan,visualizer
+          features: vulkan,visualizer,presser
         - os: windows-latest
-          features: vulkan,visualizer,d3d12,public-winapi
+          features: vulkan,visualizer,d3d12,public-winapi,presser
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v3

.gitignore

@@ -2,6 +2,10 @@
 # will have compiled files and executables
 /target/
 
+# A semi-common pattern is to have rust-analyzer compile into a separate target
+# directory like /tmp so that it doesn't conflict with other instances of cargo
+/tmp
+
 # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
 # More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
 Cargo.lock

Cargo.toml

@@ -22,6 +22,7 @@ include = [
 backtrace = "0.3"
 log = "0.4"
 thiserror = "1.0"
+presser = { version = "0.3", optional = true }
 # Only needed for vulkan.  Disable all default features as good practice,
 # such as the ability to link/load a Vulkan library.
 ash = { version = ">=0.34, <=0.37", optional = true, default-features = false, features = ["debug"] }
@@ -51,6 +52,7 @@ ash-window = "0.10.0"
 raw-window-handle = "0.4"
 winit = "0.26"
 imgui-winit-support = { version = "0.8", default-features = false, features = ["winit-26"] }
+presser = "0.3"
 
 [target.'cfg(windows)'.dev-dependencies]
 winapi = { version = "0.3.9", features = ["d3d12", "d3d12sdklayers", "dxgi1_6", "winerror", "impl-default", "impl-debug", "winuser", "windowsx", "libloaderapi"] }
@@ -94,4 +96,4 @@ d3d12 = ["windows"]
 # Expose helper functionality for winapi types to interface with gpu-allocator, which is primarily windows-rs driven
 public-winapi = ["dep:winapi"]
 
-default = ["d3d12", "vulkan"]
+default = ["d3d12", "vulkan", "presser"]

examples/vulkan-visualization/imgui_renderer.rs

@@ -309,7 +309,7 @@ impl ImGuiRenderer {
             let image_view = unsafe { device.create_image_view(&view_create_info, None) }?;
 
             // Create upload buffer
-            let (upload_buffer, upload_buffer_memory) = {
+            let (upload_buffer, mut upload_buffer_memory) = {
                 let create_info = vk::BufferCreateInfo::builder()
                     .size((font_atlas.width * font_atlas.height * 4) as u64)
                     .usage(vk::BufferUsageFlags::TRANSFER_SRC);
@@ -338,14 +338,8 @@ impl ImGuiRenderer {
             };
 
             // Copy font data to upload buffer
-            let dst = upload_buffer_memory.mapped_ptr().unwrap().cast().as_ptr();
-            unsafe {
-                std::ptr::copy_nonoverlapping(
-                    font_atlas.data.as_ptr(),
-                    dst,
-                    (font_atlas.width * font_atlas.height * 4) as usize,
-                );
-            }
+            let mut slab = upload_buffer_memory.as_mapped_slab().unwrap();
+            presser::copy_from_slice_to_offset(font_atlas.data, &mut slab, 0).unwrap();
 
             // Copy upload buffer to image
             record_and_submit_command_buffer(
@@ -633,13 +627,13 @@ impl ImGuiRenderer {
                 ],
             };
 
-            unsafe {
-                std::ptr::copy_nonoverlapping(
-                    &cbuffer_data,
-                    self.cb_allocation.mapped_ptr().unwrap().cast().as_ptr(),
-                    1,
-                )
-            };
+            let copy_record = presser::copy_to_offset(
+                &cbuffer_data,
+                &mut self.cb_allocation.as_mapped_slab().unwrap(),
+                0,
+            )
+            .unwrap();
+            assert_eq!(copy_record.copy_start_offset, 0);
         }
 
         let render_pass_begin_info = vk::RenderPassBeginInfo::builder()
@@ -715,50 +709,40 @@ impl ImGuiRenderer {
         let mut vb_offset = 0;
         let mut ib_offset = 0;
 
-        for draw_list in imgui_draw_data.draw_lists() {
-            unsafe {
-                device.cmd_bind_vertex_buffers(
-                    cmd,
-                    0,
-                    &[self.vertex_buffer],
-                    &[vb_offset as u64 * std::mem::size_of::<imgui::DrawVert>() as u64],
-                )
-            };
-            unsafe {
-                device.cmd_bind_index_buffer(
-                    cmd,
-                    self.index_buffer,
-                    ib_offset as u64 * std::mem::size_of::<imgui::DrawIdx>() as u64,
-                    vk::IndexType::UINT16,
-                )
-            };
+        let mut vb_slab = self.vb_allocation.as_mapped_slab().unwrap();
+        let mut ib_slab = self.ib_allocation.as_mapped_slab().unwrap();
 
+        for draw_list in imgui_draw_data.draw_lists() {
             {
                 let vertices = draw_list.vtx_buffer();
-                let dst_ptr = self
-                    .vb_allocation
-                    .mapped_ptr()
-                    .unwrap()
-                    .cast::<imgui::DrawVert>()
-                    .as_ptr();
-                let dst_ptr = unsafe { dst_ptr.offset(vb_offset) };
+                let copy_record =
+                    presser::copy_from_slice_to_offset(vertices, &mut vb_slab, vb_offset).unwrap();
+                vb_offset = copy_record.copy_end_offset_padded;
+
                 unsafe {
-                    std::ptr::copy_nonoverlapping(vertices.as_ptr(), dst_ptr, vertices.len())
+                    device.cmd_bind_vertex_buffers(
+                        cmd,
+                        0,
+                        &[self.vertex_buffer],
+                        &[copy_record.copy_start_offset as _],
+                    )
                 };
-                vb_offset += vertices.len() as isize;
             }
 
             {
                 let indices = draw_list.idx_buffer();
-                let dst_ptr = self
-                    .ib_allocation
-                    .mapped_ptr()
-                    .unwrap()
-                    .cast::<imgui::DrawIdx>()
-                    .as_ptr();
-                let dst_ptr = unsafe { dst_ptr.offset(ib_offset) };
-                unsafe { std::ptr::copy_nonoverlapping(indices.as_ptr(), dst_ptr, indices.len()) };
-                ib_offset += indices.len() as isize;
+                let copy_record =
+                    presser::copy_from_slice_to_offset(indices, &mut ib_slab, ib_offset).unwrap();
+                ib_offset = copy_record.copy_end_offset_padded;
+
+                unsafe {
+                    device.cmd_bind_index_buffer(
+                        cmd,
+                        self.index_buffer,
+                        copy_record.copy_start_offset as _,
+                        vk::IndexType::UINT16,
+                    )
+                };
             }
 
             for command in draw_list.commands() {

src/vulkan/mod.rs

@@ -5,6 +5,9 @@ mod visualizer;
 #[cfg(feature = "visualizer")]
 pub use visualizer::AllocatorVisualizer;
 
+#[cfg(feature = "presser")]
+mod presser;
+
 use super::allocator;
 use super::allocator::AllocationType;
 use ash::vk;

src/vulkan/presser.rs

@@ -0,0 +1,90 @@
+use super::Allocation;
+use core::convert::TryFrom;
+
+impl Allocation {
+    /// Borrow the CPU-mapped memory that backs this allocation as a [`presser::Slab`], which you can then
+    /// use to safely copy data into the raw, potentially-uninitialized buffer.
+    ///
+    /// Returns `None` if `self.mapped_ptr()` is `None`, or if `self.size()` is > `isize::MAX` because
+    /// this could lead to undefined behavior.
+    ///
+    /// # Example
+    ///
+    /// ```rust,ignore
+    /// #[repr(C, align(16))]
+    /// #[derive(Clone, Copy)]
+    /// struct MyGpuVector {
+    ///     x: f32,
+    ///     y: f32,
+    ///     z: f32,
+    /// }
+    ///
+    /// // Create some data to be sent to the GPU. Note this must be formatted correctly in terms of
+    /// // alignment of individual items and etc, as usual.
+    /// let my_gpu_data: &[MyGpuVector] = get_vertex_data();
+    ///
+    /// // Get a `presser::Slab` from our gpu_allocator::Allocation
+    /// let mut alloc_slab = my_allocation.as_mapped_slab().unwrap();
+    ///
+    /// // depending on the type of data you're copying, your vulkan device may have a minimum
+    /// // alignment requirement for that data
+    /// let min_gpu_align = my_vulkan_device_specifications.min_alignment_thing;
+    ///
+    /// let copy_record = presser::copy_from_slice_to_offset_with_align(
+    ///     my_gpu_data,
+    ///     &mut alloc_slab,
+    ///     0, // start as close to the beginning of the allocation as possible
+    ///     min_gpu_align,
+    /// );
+    ///
+    /// // the data may not have actually been copied starting at the requested start offset
+    /// // depending on the alignment of the underlying allocation, as well as the alignment requirements of
+    /// // `MyGpuVector` and the `min_gpu_align` we passed in
+    /// let actual_data_start_offset = copy_record.copy_start_offset;
+    /// ```
+    ///
+    /// # Safety
+    ///
+    /// This is technically not fully safe because we can't validate that the
+    /// GPU is not using the data in the buffer while `self` is borrowed, however trying
+    /// to validate this statically is really hard and the community has basically decided
+    /// that just calling stuff like this is fine. So, as would always be the case, ensure the GPU
+    /// is not using the data in `self` before calling this function.
+    pub fn as_mapped_slab(&mut self) -> Option<MappedAllocationSlab<'_>> {
+        let mapped_ptr = self.mapped_ptr()?.cast().as_ptr();
+        // size > isize::MAX is disallowed by `Slab` for safety reasons
+        let size = isize::try_from(self.size()).ok()?;
+        // this will always succeed since size can only be positive and < isize::MAX
+        let size = size as usize;
+
+        Some(MappedAllocationSlab {
+            _borrowed_alloc: self,
+            mapped_ptr,
+            size,
+        })
+    }
+}
+
+/// A wrapper struct over a borrowed [`Allocation`] that implements [`presser::Slab`].
+///
+/// This type should be acquired by calling [`Allocation::as_mapped_slab`].
+pub struct MappedAllocationSlab<'a> {
+    _borrowed_alloc: &'a mut Allocation,
+    mapped_ptr: *mut u8,
+    size: usize,
+}
+
+// SAFETY: See the safety comment of Allocation::as_mapped_slab above.
+unsafe impl<'a> presser::Slab for MappedAllocationSlab<'a> {
+    fn base_ptr(&self) -> *const u8 {
+        self.mapped_ptr
+    }
+
+    fn base_ptr_mut(&mut self) -> *mut u8 {
+        self.mapped_ptr
+    }
+
+    fn size(&self) -> usize {
+        self.size
+    }
+}