From 0b76352b22f4dcb112e06cd3b3cc3969407b92e2 Mon Sep 17 00:00:00 2001
From: Ivan Smirnov <i.s.smirnov@gmail.com>
Date: Sun, 2 Jan 2022 23:30:28 +0300
Subject: [PATCH] Use u32::{from_be_bytes,to_be_bytes} builtins

---
 src/consts.rs |  3 +--
 src/header.rs | 31 +++++++++----------------------
 2 files changed, 10 insertions(+), 24 deletions(-)

diff --git a/src/consts.rs b/src/consts.rs
index b143f90..2281c24 100644
--- a/src/consts.rs
+++ b/src/consts.rs
@@ -12,7 +12,6 @@ pub const QOI_HEADER_SIZE: usize = 14;
 pub const QOI_PADDING: [u8; 8] = [0, 0, 0, 0, 0, 0, 0, 0x01]; // 7 zeros and one 0x01 marker
 pub const QOI_PADDING_SIZE: usize = 8;
 
-pub const QOI_MAGIC: u32 =
-    (b'q' as u32) << 24 | (b'o' as u32) << 16 | (b'i' as u32) << 8 | (b'f' as u32);
+pub const QOI_MAGIC: u32 = u32::from_be_bytes(*b"qoif");
 
 pub const QOI_PIXELS_MAX: usize = 400_000_000;
diff --git a/src/header.rs b/src/header.rs
index a9cfc0d..e59e658 100644
--- a/src/header.rs
+++ b/src/header.rs
@@ -1,3 +1,5 @@
+use bytemuck::cast_slice;
+
 use crate::colorspace::ColorSpace;
 use crate::consts::{QOI_HEADER_SIZE, QOI_MAGIC, QOI_PIXELS_MAX};
 use crate::error::{Error, Result};
@@ -18,22 +20,6 @@ impl Default for Header {
     }
 }
 
-#[inline(always)]
-#[allow(clippy::cast_possible_truncation)]
-const fn u32_to_be(v: u32) -> [u8; 4] {
-    [
-        ((0xff00_0000 & v) >> 24) as u8,
-        ((0x00ff_0000 & v) >> 16) as u8,
-        ((0xff00 & v) >> 8) as u8,
-        (0x00ff & v) as u8,
-    ]
-}
-
-#[inline(always)]
-const fn u32_from_be(v: &[u8]) -> u32 {
-    ((v[0] as u32) << 24) | ((v[1] as u32) << 16) | ((v[2] as u32) << 8) | (v[3] as u32)
-}
-
 impl Header {
     #[inline]
     pub const fn new(width: u32, height: u32, channels: u8) -> Self {
@@ -54,9 +40,9 @@ impl Header {
     #[inline]
     pub(crate) fn encode(&self) -> [u8; QOI_HEADER_SIZE] {
         let mut out = [0; QOI_HEADER_SIZE];
-        out[..4].copy_from_slice(&u32_to_be(QOI_MAGIC));
-        out[4..8].copy_from_slice(&u32_to_be(self.width));
-        out[8..12].copy_from_slice(&u32_to_be(self.height));
+        out[..4].copy_from_slice(&QOI_MAGIC.to_be_bytes());
+        out[4..8].copy_from_slice(&self.width.to_be_bytes());
+        out[8..12].copy_from_slice(&self.height.to_be_bytes());
         out[12] = self.channels;
         out[13] = self.colorspace.into();
         out
@@ -68,9 +54,10 @@ impl Header {
         if unlikely(data.len() < QOI_HEADER_SIZE) {
             return Err(Error::InputBufferTooSmall { size: data.len(), required: QOI_HEADER_SIZE });
         }
-        let magic = u32_from_be(&data[..4]);
-        let width = u32_from_be(&data[4..8]);
-        let height = u32_from_be(&data[8..12]);
+        let v = cast_slice::<_, [u8; 4]>(&data[..12]);
+        let magic = u32::from_be_bytes(v[0]);
+        let width = u32::from_be_bytes(v[1]);
+        let height = u32::from_be_bytes(v[2]);
         let channels = data[12];
         let colorspace = ColorSpace::try_from(data[13])?;
         if unlikely(magic != QOI_MAGIC) {