Convert single hex char to integer

.gitignore

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+/target
+/Cargo.lock
+/*.iml
+/.idea

Cargo.toml

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+[package]
+name = "crypto"
+version = "0.0.1"
+authors = ["zofrex"]
+
+[[bin]]
+
+name = "hex_to_base64"

src/hex.rs

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+pub fn hex_to_dec(hex: char) -> int {
+    if hex >= '0' && hex <= '9' {
+        hex as int - '0' as int
+    }
+    else if hex >= 'a' && hex <= 'f' {
+        hex as int - 'a' as int + 10
+    }
+    else {
+        fail!("Character {} out of range", hex);
+    }
+}
+
+#[test]
+fn all_hexes() {
+    let hexes = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'];
+    for i in range(0u, hexes.len()) {
+        assert_eq!(hex_to_dec(hexes[i]), i as int);
+    }
+}
+
+#[test]
+#[should_fail]
+fn test_too_large() {
+    hex_to_dec('g');
+}
+
+#[test]
+#[should_fail]
+fn test_too_small() {
+    hex_to_dec('/');
+}

src/hex_to_base64.rs

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+mod hex;
+
+fn main() {
+    println!("Output: {}", hex::hex_to_dec('0'));
+}