mac: Add MacAddress type

The `MacAddress` structure represents a 48-bit hardware address. Using a
dedicated type instead of an array will make it easier to validate
inputs and ensure type safety.

src/mac.rs

@@ -0,0 +1,24 @@
+use std::num;
+
+
+pub struct MacAddress {
+    addr: [u8; 6],
+}
+
+
+impl MacAddress {
+    pub fn from_string(s: &str) -> Result<Self, num::ParseIntError> {
+        s.split(":")
+            .map(|b| u8::from_str_radix(b, 16))
+            .collect::<Result<Vec<u8>, _>>()
+            .and_then(|parts| {
+                let mut addr = [0u8; 6];
+                addr.copy_from_slice(&parts[..6]);
+                Ok(MacAddress { addr })
+        })
+    }
+
+    pub fn as_bytes(&self) -> &[u8; 6] {
+        &self.addr
+    }
+}

src/magic.rs

@@ -1,15 +1,16 @@
 use std::io;
 use std::net;
+use mac;
 
 
-pub struct MagicPacket {
-    addr: [u8; 6],
+pub struct MagicPacket<'a> {
+    mac: &'a mac::MacAddress,
 }
 
 
-impl MagicPacket {
-    pub fn new(addr: [u8; 6]) -> Self {
-        MagicPacket { addr }
+impl<'a> MagicPacket<'a> {
+    pub fn new(mac: &'a mac::MacAddress) -> Self {
+        MagicPacket { mac }
     }
 
     pub fn send(&self) -> io::Result<usize> {
@@ -46,7 +47,7 @@ impl<'a> Iterator for MagicPacketIterator<'a> {
         self.pos += 1;
         match self.pos {
             1 ... 6 => Some(0xff),
-            7 ... 103 => Some(self.packet.addr[(self.pos - 7) % 6]),
+            7 ... 103 => Some(self.packet.mac.as_bytes()[(self.pos - 7) % 6]),
             _ => None,
         }
     }

src/main.rs

@@ -1,6 +1,9 @@
+mod mac;
 mod magic;
 
+
 fn main() {
-    let packet = magic::MagicPacket::new([0x0c, 0x9d, 0x92, 0x0e, 0x3a, 0x41]);
+    let mac = mac::MacAddress::from_string("0c:9d:92:0e:3a:41").unwrap();
+    let packet = magic::MagicPacket::new(&mac);
     packet.send().unwrap();
 }