From 9b0fb35ed553eb9ac090cb3a567301f1eca26714 Mon Sep 17 00:00:00 2001
From: "Dustin C. Hatch" <dustin@hatch.name>
Date: Thu, 16 Aug 2018 22:53:50 -0500
Subject: [PATCH] magic: Use an iterator to generate the byte stream

Instead of explicitly writing the byte array for the magic packet
content, the `MagicPacket.send` method now delegates to
`MagicPacketIterator`. It collects the values the iterator produces,
which are determined based on the number of times the `next` method has
been called, into a vector, and then passes a slice of that vector to
the `send` method of the UDP socket.

Using a vector of course requires allocating space on the heap, so while
this method is probably not as efficient as the previous stack-allocated
static array, it is certainly cleaner and easier to understand.
---
 src/magic.rs | 64 ++++++++++++++++++++++------------------------------
 1 file changed, 27 insertions(+), 37 deletions(-)

diff --git a/src/magic.rs b/src/magic.rs
index 13f2fb2..d9b3cff 100644
--- a/src/magic.rs
+++ b/src/magic.rs
@@ -16,44 +16,34 @@ impl MagicPacket {
         let socket = net::UdpSocket::bind("0.0.0.0:0")?;
         socket.set_broadcast(true)?;
         socket.connect("255.255.255.255:9")?;
-        socket.send(&self.to_buf())
+        let buf: Vec<u8> = self.iter().collect();
+        socket.send(&buf[..102])
     }
 
-    pub fn to_buf(&self) -> [u8; 102] {
-        [
-            0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-            self.addr[0], self.addr[1], self.addr[2],
-            self.addr[3], self.addr[4], self.addr[5],
-        ]
+    fn iter(&self) -> MagicPacketIterator {
+        MagicPacketIterator {
+            packet: self,
+            pos: 0,
+        }
+    }
+}
+
+
+struct MagicPacketIterator<'a> {
+    packet: &'a MagicPacket<'a>,
+    pos: usize,
+}
+
+
+impl<'a> Iterator for MagicPacketIterator<'a> {
+    type Item = u8;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.pos += 1;
+        match self.pos {
+            1 ... 6 => Some(0xff),
+            7 ... 103 => Some(self.packet.addr[(self.pos - 7) % 6]),
+            _ => None,
+        }
     }
 }