1 files changed, 42 insertions, 0 deletions
diff --git a/dhwt-codec/src/transform.rs b/dhwt-codec/src/transform.rs
new file mode 100644
index 0000000..82bccd1
--- /dev/null
+++ b/dhwt-codec/src/transform.rs
@@ -0,0 +1,42 @@
+use crate::io::{Value, TWO};
+use std::ops::{Index, IndexMut};
+
+pub fn encode<X: Index<usize, Output = Value> + IndexMut<usize, Output = Value>>(
+    size: usize,
+    a: &mut X,
+    b: &mut X,
+) {
+    let mut k = size;
+    while k != 1 {
+        k /= 2;
+        for i in 0..k {
+            let x = a[i * 2];
+            let y = a[i * 2 + 1];
+            b[i] = x + y;
+            b[k + i] = x - y;
+        }
+        for i in 0..k {
+            a[i] = b[i]
+        }
+    }
+}
+
+pub fn decode<X: Index<usize, Output = Value> + IndexMut<usize, Output = Value>>(
+    size: usize,
+    a: &mut X,
+    b: &mut X,
+) {
+    let mut k = 1;
+    while k != size {
+        for i in 0..k {
+            let avr = a[i] / TWO;
+            let spread = a[i + k] / TWO;
+            b[i * 2] = avr + spread;
+            b[i * 2 + 1] = avr - spread;
+        }
+        k *= 2;
+        for i in 0..k {
+            a[i] = b[i]
+        }
+    }
+}