Mark from_cidr as deprecated

- Also refactored a bit
- Updated doc tests

src/common.rs

@@ -1,3 +1,5 @@
+use std::net::Ipv4Addr;
+
 #[derive(Debug,Clone,PartialEq,Eq)]
 pub enum IpNetworkError {
     InvalidAddr(String),
@@ -22,3 +24,17 @@ pub fn parse_prefix(prefix: &str, max: u8) -> Result<u8, IpNetworkError> {
         Ok(mask)
     }
 }
+
+pub fn parse_addr(addr: &str) -> Result<Ipv4Addr, IpNetworkError> {
+    let addr_parts = addr.split('.').map(|b| b.parse::<u8>());
+    let mut bytes = [0; 4];
+    for (i, byte) in addr_parts.enumerate() {
+        if i >= 4 {
+            return Err(IpNetworkError::InvalidAddr(format!("More than 4 bytes: {}", addr)));
+        }
+        bytes[i] = try!(byte.map_err(|_| {
+                IpNetworkError::InvalidAddr(format!("All bytes not 0-255: {}", addr))
+            }));
+    }
+    Ok(Ipv4Addr::new(bytes[0], bytes[1], bytes[2], bytes[3]))
+}