From 931d256d62a1a20c8ba8a8b6726fb1d7167f1d68 Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Sun, 4 Apr 2021 15:42:36 +0530
Subject: speed up pixmap drawing!

---
 src/utils.rs | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

(limited to 'src/utils.rs')

diff --git a/src/utils.rs b/src/utils.rs
index bee5782..ab446f4 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -108,3 +108,36 @@ pub fn load_file<P: AsRef<Path>>(path: P) -> Result<Image, io::Error> {
     image.read_to_end(&mut buf)?;
     Ok(Image::decode(&mut (Cursor::new(buf))).unwrap()) // TODO: obi error
 }
+
+pub fn compress<T: PartialEq + Clone>(scanline: &[T]) -> Vec<(T, usize)> {
+    let mut runs = vec![];
+    if scanline.is_empty() {
+        return runs;
+    }
+    let mut idx = 0;
+    loop {
+        let first = &scanline[idx];
+        let run_length = scanline[idx..]
+            .iter()
+            .take_while(|&item| item == first)
+            .count();
+
+        runs.push((first.clone(), run_length));
+
+        idx += run_length;
+        if idx > scanline.len() - 1 {
+            break;
+        }
+    }
+    runs
+}
+
+#[cfg(test)]
+mod tests {
+    use super::compress;
+    #[test]
+    fn compression() {
+        let sl = [1, 1, 1, 2, 2, 2];
+        assert_eq!(compress(&sl), vec![(1, 3), (2, 3)]);
+    }
+}
-- 
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