From 5795fa79438f16e415cfb20e9288c4a5eb1369fd Mon Sep 17 00:00:00 2001
From: Jay Oster <jay@pubnub.com>
Date: Sun, 27 Oct 2019 19:50:15 -0700
Subject: [PATCH] Add include_spv!() macro, donated by Ralith (#26)

---
 Cargo.lock       |  1 -
 Cargo.toml       |  1 -
 src/lib.rs       |  7 ++++---
 src/macros.rs    | 42 ++++++++++++++++++++++++++++++++++++++++++
 src/renderers.rs | 22 +++-------------------
 5 files changed, 49 insertions(+), 24 deletions(-)
 create mode 100644 src/macros.rs

diff --git a/Cargo.lock b/Cargo.lock
index 411d663..cb78aad 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -702,7 +702,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "pixels"
 version = "0.0.1"
 dependencies = [
- "byteorder 1.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "env_logger 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "pixels-mocks 0.1.0",
diff --git a/Cargo.toml b/Cargo.toml
index b3b5fba..7974122 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -11,7 +11,6 @@ categories = ["graphics", "rendering"]
 license = "MIT"
 
 [dependencies]
-byteorder = "1.3"
 wgpu = { git = "https://github.com/gfx-rs/wgpu-rs", rev = "012d08d64de924da93289c2b51fb06b22d7348cf" }
 
 [dev-dependencies]
diff --git a/src/lib.rs b/src/lib.rs
index 9ad5082..65738b5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -16,14 +16,15 @@ use std::error::Error as StdError;
 use std::fmt;
 use std::rc::Rc;
 
+pub use crate::macros::*;
+pub use crate::render_pass::{BoxedRenderPass, Device, Queue, RenderPass};
+use crate::renderers::Renderer;
 pub use wgpu;
 use wgpu::{Extent3d, TextureView};
 
+mod macros;
 mod render_pass;
-pub use render_pass::{BoxedRenderPass, Device, Queue, RenderPass};
-
 mod renderers;
-use renderers::Renderer;
 
 type RenderPassFactory = Box<dyn Fn(Device, Queue, &TextureView, &Extent3d) -> BoxedRenderPass>;
 
diff --git a/src/macros.rs b/src/macros.rs
new file mode 100644
index 0000000..f91746a
--- /dev/null
+++ b/src/macros.rs
@@ -0,0 +1,42 @@
+//! Provides a macro and type for including SPIR-V shaders in const data.
+//!
+//! In an ideal world, a shader will be compiled at build-time directly into the executable. This
+//! is opposed to the typical method of including a shader, which reads a GLSL source code file
+//! from the file system at start, compiles it, and sends it to the GPU. That process adds a
+//! non-trivial amount of time to startup, and additional error handling code at runtime.
+//!
+//! This macro moves all of that complexity to build-time. At least for the SPIR-V part of the
+//! shader pipeline. (`gfx-hal` backends have their own SPIR-V-to-native compilers at runtime.)
+//!
+//! Cribbed with permission from Ralith
+//! See: https://github.com/MaikKlein/ash/pull/245
+
+/// Include correctly aligned and typed precompiled SPIR-V
+///
+/// Does not account for endianness mismatches between the SPIR-V file and the target. See
+/// [`wgpu::read_spirv`] for a more general solution.
+#[macro_export]
+macro_rules! include_spv {
+    ($path:expr) => {
+        &$crate::Align4(*include_bytes!($path)) as &$crate::Spirv
+    };
+}
+
+/// Type returned by `include_spv`, convertible to `&[u32]`
+///
+/// The definition of this type is unstable.
+pub type Spirv = Align4<[u8]>;
+
+impl std::ops::Deref for Spirv {
+    type Target = [u32];
+    fn deref(&self) -> &[u32] {
+        #[allow(clippy::cast_ptr_alignment)]
+        unsafe {
+            std::slice::from_raw_parts(self.0.as_ptr() as *const u32, self.0.len() / 4)
+        }
+    }
+}
+
+#[repr(align(4))]
+#[doc(hidden)]
+pub struct Align4<T: ?Sized>(pub T);
diff --git a/src/renderers.rs b/src/renderers.rs
index dcd07d5..39ffd27 100644
--- a/src/renderers.rs
+++ b/src/renderers.rs
@@ -1,8 +1,8 @@
-use byteorder::{ByteOrder, LittleEndian};
 use std::fmt;
 use std::rc::Rc;
 use wgpu::{self, Extent3d, TextureView};
 
+use crate::include_spv;
 use crate::render_pass::{BoxedRenderPass, Device, Queue, RenderPass};
 
 /// Renderer implements [`RenderPass`].
@@ -24,24 +24,8 @@ impl Renderer {
         texture_view: &TextureView,
         texture_size: &Extent3d,
     ) -> BoxedRenderPass {
-        let vert_spv = include_bytes!("../shaders/vert.spv");
-        let mut vert = Vec::new();
-        vert.resize_with(
-            vert_spv.len() / std::mem::size_of::<u32>(),
-            Default::default,
-        );
-        LittleEndian::read_u32_into(vert_spv, &mut vert);
-
-        let frag_spv = include_bytes!("../shaders/frag.spv");
-        let mut frag = Vec::new();
-        frag.resize_with(
-            frag_spv.len() / std::mem::size_of::<u32>(),
-            Default::default,
-        );
-        LittleEndian::read_u32_into(frag_spv, &mut frag);
-
-        let vs_module = device.create_shader_module(&vert);
-        let fs_module = device.create_shader_module(&frag);
+        let vs_module = device.create_shader_module(include_spv!("../shaders/vert.spv"));
+        let fs_module = device.create_shader_module(include_spv!("../shaders/frag.spv"));
 
         // Create a texture sampler with nearest neighbor
         let sampler = device.create_sampler(&wgpu::SamplerDescriptor {