First baudot code implementation works

.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.
+[[package]]
+name = "lazy_static"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+
+[[package]]
+name = "rusty-tty"
+version = "0.1.0"
+dependencies = [
+ "lazy_static",
+]

Cargo.toml

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+[package]
+name = "rusty-tty"
+version = "0.1.0"
+authors = ["Sebastian <sebastian@sebastians-site.de>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+lazy_static = "*"

src/baudot.rs

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+use std::collections::HashMap;
+
+const LETTERS: &[u8] = b"\0E\nA SIU\rDRJNFCKTZLWHYPQOBG\0MXV\0";
+const FIGURES: &[u8] = b"\03\n- \x0787\r\x054',!:(5\")2#6019?&\0./;\0";
+
+lazy_static! {
+    static ref INV_LETTERS: HashMap<u8, u8> = LETTERS
+        .iter()
+        .enumerate()
+        .map(|(c, f)| (*f, c as u8))
+        .collect();
+    static ref INV_FIGURES: HashMap<u8, u8> = FIGURES
+        .iter()
+        .enumerate()
+        .map(|(c, f)| (*f, c as u8))
+        .collect();
+}
+
+fn letter_from_code(code: u8) -> Option<u8> {
+    if code >= (LETTERS.len() as u8) {
+        None
+    } else {
+        Some(LETTERS[code as usize])
+    }
+}
+
+fn figure_from_code(code: u8) -> Option<u8> {
+    if code >= (FIGURES.len() as u8) {
+        None
+    } else {
+        Some(FIGURES[code as usize])
+    }
+}
+
+fn code_from_letter(letter: &u8) -> Option<u8> {
+    INV_LETTERS.get(letter).cloned()
+}
+
+fn code_from_figure(figure: &u8) -> Option<u8> {
+    INV_FIGURES.get(figure).cloned()
+}
+
+const SHIFT_FIGURES: u8 = 0b11011u8;
+const SHIFT_LETTERS: u8 = 0b11111u8;
+
+#[derive(Copy, Clone)]
+enum ShiftState {
+    None,
+    Letters,
+    Figures,
+}
+
+pub fn encode(msg: &str) -> Result<Vec<u8>, u8> {
+    let mut res = Vec::<u8>::new();
+
+    let mut shift = ShiftState::None;
+
+    for &byte in msg.to_ascii_uppercase().as_bytes().iter() {
+        let letter = code_from_letter(&byte);
+        let figure = code_from_figure(&byte);
+        match (letter, figure, shift) {
+            (Some(l), Some(_), ShiftState::None) => {
+                res.push(SHIFT_LETTERS);
+                shift = ShiftState::Letters;
+                res.push(l);
+            }
+            (Some(l), Some(_), _) => res.push(l),
+            (Some(l), None, ShiftState::Letters) => res.push(l),
+            (Some(l), None, _) => {
+                res.push(SHIFT_LETTERS);
+                shift = ShiftState::Letters;
+                res.push(l);
+            }
+            (None, Some(f), ShiftState::Figures) => res.push(f),
+            (None, Some(f), _) => {
+                res.push(SHIFT_FIGURES);
+                shift = ShiftState::Figures;
+                res.push(f);
+            }
+            (None, None, _) => return Err(byte),
+        }
+    }
+
+    Ok(res)
+}
+
+pub fn decode(msg: &Vec<u8>) -> Result<String, u8> {
+    let mut res = String::new();
+
+    // Lets assume this is a sane starting point.
+    let mut shift = ShiftState::Letters;
+
+    for &code in msg.iter() {
+        match (code, shift) {
+            (SHIFT_LETTERS, _) => shift = ShiftState::Letters,
+            (SHIFT_FIGURES, _) => shift = ShiftState::Figures,
+            (c, ShiftState::Letters) => match letter_from_code(c) {
+                Some(l) => res.push(l as char),
+                None => return Err(c),
+            },
+            (c, ShiftState::Figures) => match figure_from_code(c) {
+                Some(l) => res.push(l as char),
+                None => return Err(c),
+            },
+            (_, ShiftState::None) => panic!("Shift state is expectedly None"),
+        }
+    }
+
+    Ok(res)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_encode() {
+        let encoded = encode("kaufen sie jede woche vier gute bequeme pelze xy 1234567890");
+        assert_eq!(
+            encoded,
+            Ok(vec![
+                31, 15, 3, 7, 13, 1, 12, 4, 5, 6, 1, 4, 11, 1, 9, 1, 4, 19, 24, 14, 20, 1, 4, 30,
+                6, 1, 10, 4, 26, 7, 16, 1, 4, 25, 1, 23, 7, 1, 28, 1, 4, 22, 1, 18, 17, 1, 4, 29,
+                21, 4, 27, 23, 19, 1, 10, 16, 21, 7, 6, 24, 22
+            ])
+        );
+    }
+
+    #[test]
+    fn test_decode() {
+        let kaufen_schleife: Vec<u8> = vec![
+            31, 15, 3, 7, 13, 1, 12, 4, 5, 6, 1, 4, 11, 1, 9, 1, 4, 19, 24, 14, 20, 1, 4, 30, 6, 1,
+            10, 4, 26, 7, 16, 1, 4, 25, 1, 23, 7, 1, 28, 1, 4, 22, 1, 18, 17, 1, 4, 29, 21, 4, 27,
+            23, 19, 1, 10, 16, 21, 7, 6, 24, 22,
+        ];
+
+        let decoded = decode(&kaufen_schleife);
+        assert_eq!(
+            Ok(String::from(
+                "KAUFEN SIE JEDE WOCHE VIER GUTE BEQUEME PELZE XY 1234567890"
+            )),
+            decoded
+        )
+    }
+}

src/main.rs

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+#[macro_use]
+extern crate lazy_static;
+
+mod baudot;
+
+fn main() {
+    println!("Hello, world!");
+}