From 28e067fc983aa8241c782b04406abd9c538a0986 Mon Sep 17 00:00:00 2001
From: Camil Staps
Date: Mon, 2 May 2016 22:51:37 +0200
Subject: Project 2: simple DNS resolver

---
 project2/proj2_s4498062/dns/regexes.py | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 project2/proj2_s4498062/dns/regexes.py

(limited to 'project2/proj2_s4498062/dns/regexes.py')

diff --git a/project2/proj2_s4498062/dns/regexes.py b/project2/proj2_s4498062/dns/regexes.py
new file mode 100644
index 0000000..48c28c9
--- /dev/null
+++ b/project2/proj2_s4498062/dns/regexes.py
@@ -0,0 +1,29 @@
+"""Regexes used in the DNS protocol"""
+
+def grpm(regex):
+    """Make a matching group"""
+    return grp(regex, matching=True)
+
+def grp(regex, matching=False):
+    """Make a group"""
+    return r'(' + (r'' if matching else r'?:') + regex + r')'
+
+def opt(regex):
+    """Make an optional group"""
+    return grp(grp(regex) + r'?')
+
+def regex_opt_r(*regexes):
+    """Make a group that matches one of the given regexes"""
+    return grp(r'|'.join(regexes))
+
+DIGIT = r'\d'
+LETTER = r'[a-zA-Z]'
+LETDIG = grp(regex_opt_r(DIGIT, LETTER))
+LETDIGHYP = grp(regex_opt_r(LETDIG, r'-'))
+LDHSTR = grp(LETDIGHYP + r'+')
+LABEL = grp(LETTER + opt(opt(LDHSTR) + LETDIG))
+SUBDOMAIN = grp(grpm(grp(LABEL + r'\.') + r'*') + grpm(LABEL))
+DOMAIN = regex_opt_r(SUBDOMAIN, r' ')
+
+IP = r'(?:(?:\d{1,3}\.){3}\d{1,3})'
+
-- 
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