From a70ce10bed85ee90899c41b783bc5999835eb9d9 Mon Sep 17 00:00:00 2001
From: Matias Fontanini <matias.fontanini@gmail.com>
Date: Sat, 19 Mar 2016 16:26:00 -0700
Subject: [PATCH] Add IPv4Address::from_prefix_length

---
 include/tins/ip_address.h | 7 +++++++
 src/address_range.cpp     | 7 ++-----
 src/ip_address.cpp        | 6 +++++-
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/include/tins/ip_address.h b/include/tins/ip_address.h
index 1fdf636..8b7eff4 100644
--- a/include/tins/ip_address.h
+++ b/include/tins/ip_address.h
@@ -53,6 +53,13 @@ public:
      */
     static const IPv4Address broadcast;
 
+    /**
+     * \brief Constructs an IPv4 address from a prefix length
+     *
+     * \param prefix_length The length of the prefix
+     */
+    static IPv4Address from_prefix_length(uint32_t prefix_length);
+
     /**
      * \brief Constructor taking a const char*.
      * 
diff --git a/src/address_range.cpp b/src/address_range.cpp
index 00291a9..89df754 100644
--- a/src/address_range.cpp
+++ b/src/address_range.cpp
@@ -39,15 +39,12 @@ IPv4Range operator/(const IPv4Address& addr, int mask) {
     if (mask > 32) {
         throw logic_error("Prefix length cannot exceed 32");
     }
-    return IPv4Range::from_mask(
-        addr, 
-        IPv4Address(Endian::host_to_be(0xffffffff << (32 - mask)))
-    );
+    return IPv4Range::from_mask(addr, IPv4Address::from_prefix_length(mask));
 }
 
 IPv6Range operator/(const IPv6Address& addr, int mask) {
     if (mask > 128) {
-        throw std::logic_error("Prefix length cannot exceed 128");
+        throw logic_error("Prefix length cannot exceed 128");
     }
     return IPv6Range::from_mask(addr, IPv6Address::from_prefix_length(mask));
 }
diff --git a/src/ip_address.cpp b/src/ip_address.cpp
index 7b8e898..e0e97d3 100644
--- a/src/ip_address.cpp
+++ b/src/ip_address.cpp
@@ -54,7 +54,11 @@ const AddressRange<IPv4Address> private_ranges[] = {
 
 const AddressRange<IPv4Address> loopback_range = IPv4Address("127.0.0.0") / 8;
 const AddressRange<IPv4Address> multicast_range = IPv4Address("224.0.0.0") / 4;
-    
+
+IPv4Address IPv4Address::from_prefix_length(uint32_t prefix_length) {
+    return IPv4Address(Endian::host_to_be(0xffffffff << (32 - prefix_length)));
+}
+
 IPv4Address::IPv4Address(uint32_t ip) 
 : ip_addr_(Endian::be_to_host(ip)) {