extensions/khr: Add VK_KHR_external_fence_fd wrapper (#413)

This extension wrapper is identical to the one for
VK_KHR_external_semaphore_fd introduced in #395 with 'semaphore'
substitued for 'fence'.

ash/src/extensions/khr/external_fence_fd.rs

@@ -0,0 +1,51 @@
+use crate::prelude::*;
+use crate::version::{DeviceV1_0, InstanceV1_0};
+use crate::vk;
+use std::ffi::CStr;
+use std::mem;
+
+#[derive(Clone)]
+pub struct ExternalFenceFd {
+    handle: vk::Device,
+    external_fence_fd_fn: vk::KhrExternalFenceFdFn,
+}
+
+impl ExternalFenceFd {
+    pub fn new<I: InstanceV1_0, D: DeviceV1_0>(instance: &I, device: &D) -> Self {
+        let external_fence_fd_fn = vk::KhrExternalFenceFdFn::load(|name| unsafe {
+            mem::transmute(instance.get_device_proc_addr(device.handle(), name.as_ptr()))
+        });
+        Self {
+            handle: device.handle(),
+            external_fence_fd_fn,
+        }
+    }
+
+    pub fn name() -> &'static CStr {
+        vk::KhrExternalFenceFdFn::name()
+    }
+
+    #[doc = "<https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkImportFenceFdKHR.html>"]
+    pub unsafe fn import_fence_fd(&self, import_info: &vk::ImportFenceFdInfoKHR) -> VkResult<()> {
+        self.external_fence_fd_fn
+            .import_fence_fd_khr(self.handle, import_info)
+            .result()
+    }
+
+    #[doc = "<https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkGetFenceFdKHR.html>"]
+    pub unsafe fn get_fence_fd(&self, get_info: &vk::FenceGetFdInfoKHR) -> VkResult<i32> {
+        let mut fd = -1;
+
+        self.external_fence_fd_fn
+            .get_fence_fd_khr(self.handle, get_info, &mut fd)
+            .result_with_success(fd)
+    }
+
+    pub fn fp(&self) -> &vk::KhrExternalFenceFdFn {
+        &self.external_fence_fd_fn
+    }
+
+    pub fn device(&self) -> vk::Device {
+        self.handle
+    }
+}

ash/src/extensions/khr/mod.rs

@@ -6,6 +6,7 @@ pub use self::deferred_host_operations::DeferredHostOperations;
 pub use self::display::Display;
 pub use self::display_swapchain::DisplaySwapchain;
 pub use self::draw_indirect_count::DrawIndirectCount;
+pub use self::external_fence_fd::ExternalFenceFd;
 pub use self::external_memory_fd::ExternalMemoryFd;
 pub use self::external_semaphore_fd::ExternalSemaphoreFd;
 pub use self::get_memory_requirements2::GetMemoryRequirements2;
@@ -30,6 +31,7 @@ mod deferred_host_operations;
 mod display;
 mod display_swapchain;
 mod draw_indirect_count;
+mod external_fence_fd;
 mod external_memory_fd;
 mod external_semaphore_fd;
 mod get_memory_requirements2;