Reorganize rotate.rs, separate rotations into their own functions

codecs/rotate/rotate.rs

@@ -1,4 +1,4 @@
-use std::slice::from_raw_parts_mut;
+use std::slice::{from_raw_parts, from_raw_parts_mut};
 
 // This function is taken from Zachary Dremann
 // https://github.com/GoogleChromeLabs/squoosh/pull/462
@@ -24,23 +24,28 @@ impl<T> HardUnwrap<T> for Option<T> {
 
 const TILE_SIZE: usize = 16;
 
-#[no_mangle]
+fn get_buffers<'a>(width: usize, height: usize) -> (&'a [u32], &'a mut [u32]) {
-fn rotate(width: usize, height: usize, rotate: usize) {
     let num_pixels = width * height;
-    let in_b: &mut [u32];
+    let in_b: &[u32];
     let out_b: &mut [u32];
     unsafe {
-        in_b = from_raw_parts_mut::<u32>(8 as *mut u32, num_pixels);
+        in_b = from_raw_parts::<u32>(8 as *const u32, num_pixels);
         out_b = from_raw_parts_mut::<u32>((num_pixels * 4 + 8) as *mut u32, num_pixels);
     }
+    return (in_b, out_b);
+}
 
-    match rotate {
+#[inline(never)]
-        0 => {
+fn rotate_0(width: usize, height: usize) {
+    let (in_b, out_b) = get_buffers(width, height);
     for (in_p, out_p) in in_b.iter().zip(out_b.iter_mut()) {
         *out_p = *in_p;
     }
 }
-        90 => {
+
+#[inline(never)]
+fn rotate_90(width: usize, height: usize) {
+    let (in_b, out_b) = get_buffers(width, height);
     let new_width = height;
     let _new_height = width;
     for y_start in (0..height).step_by(TILE_SIZE) {
@@ -59,12 +64,18 @@ fn rotate(width: usize, height: usize, rotate: usize) {
         }
     }
 }
-        180 => {
+
+#[inline(never)]
+fn rotate_180(width: usize, height: usize) {
+    let (in_b, out_b) = get_buffers(width, height);
     for (in_p, out_p) in in_b.iter().zip(out_b.iter_mut().rev()) {
         *out_p = *in_p;
     }
 }
-        270 => {
+
+#[inline(never)]
+fn rotate_270(width: usize, height: usize) {
+    let (in_b, out_b) = get_buffers(width, height);
     let new_width = height;
     let new_height = width;
     for y_start in (0..height).step_by(TILE_SIZE) {
@@ -82,6 +93,14 @@ fn rotate(width: usize, height: usize, rotate: usize) {
         }
     }
 }
+
+#[no_mangle]
+fn rotate(width: usize, height: usize, rotate: usize) {
+    match rotate {
+        0 => rotate_0(width, height),
+        90 => rotate_90(width, height),
+        180 => rotate_180(width, height),
+        270 => rotate_270(width, height),
         _ => std::process::abort(),
     }
 }