Add Buffer::pair_from_iter to make it one step easier for staging data to the device

vulkano/src/buffer/mod.rs

@@ -71,6 +71,7 @@
 //! [the `shader` module documentation]: crate::shader
 
 pub use self::{subbuffer::*, sys::*, usage::*};
+use crate::memory::allocator::MemoryTypeFilter;
 use crate::{
     device::{physical::PhysicalDevice, Device, DeviceOwned},
     macros::{vulkan_bitflags, vulkan_enum},
@@ -291,6 +292,51 @@ impl Buffer {
         Ok(buffer)
     }
 
+    /// Creates a staging buffer with the data `iter` and a device-local buffer with the same size.
+    /// Returns a tuple of [`Subbuffer`]s (staging, device-local) spanning the whole buffers.
+    /// Useful for passing into `copy_buffer` command as (source, destination).
+    pub fn pair_from_iter<T, I>(
+        allocator: Arc<dyn MemoryAllocator>,
+        iter: I,
+        usage: BufferUsage,
+    ) -> Result<(Subbuffer<[T]>, Subbuffer<[T]>), Validated<AllocateBufferError>>
+    where
+        T: BufferContents,
+        I: IntoIterator<Item = T>,
+        I::IntoIter: ExactSizeIterator,
+    {
+        let iter = iter.into_iter();
+
+        let device_local_buffer = Buffer::new_slice::<T>(
+            allocator.clone(),
+            BufferCreateInfo {
+                usage: BufferUsage::TRANSFER_DST | usage,
+                ..Default::default()
+            },
+            AllocationCreateInfo {
+                memory_type_filter: MemoryTypeFilter::PREFER_DEVICE,
+                ..Default::default()
+            },
+            iter.len() as DeviceSize,
+        )?;
+
+        let staging_buffer = Buffer::from_iter(
+            allocator.clone(),
+            BufferCreateInfo {
+                usage: BufferUsage::TRANSFER_SRC,
+                ..Default::default()
+            },
+            AllocationCreateInfo {
+                memory_type_filter: MemoryTypeFilter::PREFER_HOST
+                    | MemoryTypeFilter::HOST_SEQUENTIAL_WRITE,
+                ..Default::default()
+            },
+            iter,
+        )?;
+
+        Ok((staging_buffer, device_local_buffer))
+    }
+
     /// Creates a new uninitialized `Buffer` for sized data. Returns a [`Subbuffer`] spanning the
     /// whole buffer.
     ///