From bf215ef88e18de54396392ddd9042c880c79ca86 Mon Sep 17 00:00:00 2001
From: Robbert van der Helm <mail@robbertvanderhelm.nl>
Date: Sun, 6 Mar 2022 14:41:40 +0100
Subject: [PATCH] Add a Hann function for the STFT helper

---
 src/util.rs        |  1 +
 src/util/window.rs | 17 +++++++++++++++++
 2 files changed, 18 insertions(+)
 create mode 100644 src/util/window.rs

diff --git a/src/util.rs b/src/util.rs
index ef8f7f67..f15dc5d7 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -1,6 +1,7 @@
 //! General conversion functions and utilities.
 
 mod stft;
+pub mod window;
 
 pub use stft::StftHelper;
 
diff --git a/src/util/window.rs b/src/util/window.rs
new file mode 100644
index 00000000..2abae9e8
--- /dev/null
+++ b/src/util/window.rs
@@ -0,0 +1,17 @@
+//! Windowing functions, useful in conjuction with [`StftHelper`][super::StftHelper].
+
+use std::f32;
+
+/// A Hann window function.
+///
+/// <https://en.wikipedia.org/wiki/Hann_function>
+pub fn hann(size: usize) -> Vec<f32> {
+    // We want to scale `[0, size]` to `[0, pi]`.
+    let scale = (size as f32 - 1.0).recip() * f32::consts::PI;
+    (0..size)
+        .map(|i| {
+            let sin = (i as f32 * scale).sin();
+            sin * sin
+        })
+        .collect()
+}