From 58dccf697fcfcf3c411974bb4bb03a1393044559 Mon Sep 17 00:00:00 2001
From: Astro <astro@spaceboyz.net>
Date: Thu, 8 Apr 2021 02:57:50 +0200
Subject: [PATCH] netmasks.nix: turn into code

---
 nix/lib/netmasks.nix | 68 +++++++++++++++++++++-----------------------
 1 file changed, 33 insertions(+), 35 deletions(-)

diff --git a/nix/lib/netmasks.nix b/nix/lib/netmasks.nix
index 7ceb270..c40a42c 100644
--- a/nix/lib/netmasks.nix
+++ b/nix/lib/netmasks.nix
@@ -1,35 +1,33 @@
-{
-  "0" = "0.0.0.0";
-  "1" = "128.0.0.0";
-  "2" = "192.0.0.0";
-  "3" = "224.0.0.0";
-  "4" = "240.0.0.0";
-  "5" = "248.0.0.0";
-  "6" = "252.0.0.0";
-  "7" = "254.0.0.0";
-  "8" = "255.0.0.0";
-  "9" = "255.128.0.0";
-  "10" = "255.192.0.0";
-  "11" = "255.224.0.0";
-  "12" = "255.240.0.0";
-  "13" = "255.248.0.0";
-  "14" = "255.252.0.0";
-  "15" = "255.254.0.0";
-  "16" = "255.255.0.0";
-  "17" = "255.255.128.0";
-  "18" = "255.255.192.0";
-  "19" = "255.255.224.0";
-  "20" = "255.255.240.0";
-  "21" = "255.255.248.0";
-  "22" = "255.255.252.0";
-  "23" = "255.255.254.0";
-  "24" = "255.255.255.0";
-  "25" = "255.255.255.128";
-  "26" = "255.255.255.192";
-  "27" = "255.255.255.224";
-  "28" = "255.255.255.240";
-  "29" = "255.255.255.248";
-  "30" = "255.255.255.252";
-  "31" = "255.255.255.254";
-  "32" = "255.255.255.255";
-}
+let
+  pow2 = n:
+    if n <= 0
+    then 1
+    else 2 * (pow2 (n - 1));
+  octet = n:
+    if n == 0
+    then 0
+    else (pow2 (8 - n)) + (octet (n - 1));
+
+  netmask = len:
+    builtins.concatStringsSep "." (
+      map (byte:
+        toString (
+          if 8 * (byte + 1) <= len
+          then 255
+          else if 8 * byte <= len
+          then octet (len - (8 * byte))
+          else 0
+        )
+      ) [0 1 2 3]
+    );
+  
+  keys = n:
+    if n < 33
+    then [n] ++ keys (n + 1)
+    else [];
+in
+builtins.foldl' (netmasks: n:
+  netmasks // {
+    "${toString n}" = netmask n;
+  }
+) {} (keys 0)