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crypto/caeser_cipher/.gitignore

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+# Generated by Cargo
+# will have compiled files and executables
+debug/
+target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
+
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb

crypto/caeser_cipher/Cargo.toml

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+[package]
+name = "caeser_cipher"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

crypto/caeser_cipher/src/main.rs

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+fn main() {
+    println!("Hello, world!");
+}
+
+fn caesar(plain: &str, rshift: u8) -> String {
+    let alphabet = "abcdefghijklmnopqrstuvwxyz";
+    let mut out = String::new();
+    for c in plain.chars() {
+        if !c.is_alphabetic() {
+            out.push(c);
+            continue;
+        }
+        let num = (alphabet
+            .bytes()
+            .position(|a| a == c.to_lowercase().next().unwrap() as u8)
+            .unwrap() as u8
+            + rshift)
+            % 26;
+        let a = alphabet.chars().nth(num as usize).unwrap();
+        let a = if c.is_uppercase() {
+            a.to_uppercase().next().unwrap()
+        } else {
+            a
+        };
+        out.push(a);
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn rot13() {
+        let message = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+        let shift = 13;
+        let out = "NOPQRSTUVWXYZABCDEFGHIJKLMnopqrstuvwxyzabcdefghijklm";
+        assert_eq!(caesar(message, shift), out);
+    }
+
+    #[test]
+    fn wiki_caesar() {
+        let message = "THE QUICK BROWN FOX JUMPS OVER THE LAZY DOG";
+        let shift = 23;
+        let out = "QEB NRFZH YOLTK CLU GRJMP LSBO QEB IXWV ALD";
+        assert_eq!(caesar(message, shift), out);
+    }
+}