rle

.gitignore

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+/target

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "text-compression"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "text-compression"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

src/main.rs

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+use std::io::{self, Read};
+
+mod rle;
+
+fn main() -> Result<(), io::Error> {
+    let mut buf = Vec::new();
+    let len_src = io::stdin().read_to_end(&mut buf)?;
+
+    println!("Original size: {len_src}");
+
+    let len_rle = rle::Encoder::new(&buf).count() * 2;
+    println!("Rle'd size:    {len_rle}");
+
+    Ok(())
+}

src/rle.rs

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+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Run {
+    pub count: u8,
+    pub byte: u8,
+}
+
+#[derive(Debug, Clone)]
+pub struct Encoder<'src> {
+    src: &'src [u8],
+}
+
+impl<'src> Encoder<'src> {
+    pub fn new(src: &'src [u8]) -> Self {
+        Self { src }
+    }
+}
+
+impl Iterator for Encoder<'_> {
+    type Item = Run;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let &byte = self.src.first()?;
+
+        let (count, _) = self
+            .src
+            .iter()
+            .copied()
+            .take(256)
+            .enumerate()
+            .find(|&(_i, c)| c != byte)
+            .unwrap_or((self.src.len(), 0));
+
+        self.src = &self.src[count..];
+
+        Some(Run {
+            count: count.try_into().unwrap(),
+            byte,
+        })
+    }
+}