From 0de572feafca12d1a69ef8d2b2f3e6f0e998b12b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marcin=20Wo=C5=BAniak?= <y0rune@aol.com>
Date: Mon, 22 Jan 2024 00:19:18 +0100
Subject: [PATCH] Added function mask2cidr in .zshrc

---
 .zshrc | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/.zshrc b/.zshrc
index 0bfb820..e088814 100644
--- a/.zshrc
+++ b/.zshrc
@@ -16,6 +16,24 @@ gbranch() {
     echo -e "$(git branch "$@")"
 }
 
+mask2cidr() {
+    local mask=$1
+
+    # In RFC 4632 netmasks there's no "255." after a non-255 byte in the mask
+    local left_stripped_mask=${mask##*255.}
+    local len_mask=${#mask}
+    local len_left_stripped_mask=${#left_stripped_mask}
+
+    local conversion_table=0^^^128^192^224^240^248^252^254^
+    local number_of_bits_stripped=$((($len_mask - $len_left_stripped_mask) * 2))
+    local signifacant_octet=${left_stripped_mask%%.*}
+
+    local right_stripped_conversion_table=${conversion_table%%$signifacant_octet*}
+    local len_right_stripped_conversion_table=${#right_stripped_conversion_table}
+    local number_of_bits_from_conversion_table=$((len_right_stripped_conversion_table / 4))
+    echo $(($number_of_bits_stripped + $number_of_bits_from_conversion_table))
+}
+
 [ -f /etc/gentoo-release ] && export ZSH="/usr/share/zsh/site-contrib/oh-my-zsh"
 [ -f /etc/centos-release ] && export ZSH="$HOME/.oh-my-zsh"
 [ -f /etc/debian_version ] && export ZSH="$HOME/.oh-my-zsh"