From 3efdb35480dd6fa656d0728cab5c8dc76eaba24c Mon Sep 17 00:00:00 2001
From: Jonas Gunz <himself@jonasgunz.de>
Date: Sat, 30 Nov 2019 12:29:12 +0100
Subject: added qname_to_fqdn(), working

---
 src/dns.c | 27 ++++++++++++++++++++++++---
 src/dns.h |  4 +++-
 2 files changed, 27 insertions(+), 4 deletions(-)

(limited to 'src')

diff --git a/src/dns.c b/src/dns.c
index 54ad504..7c94c8a 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -2,7 +2,6 @@
 
 int fqdn_to_qname( char* _source, int _sourcelen, char* _sink ,int _sinklen )
 {
-	// TODO Opttimize
 	int i;
 	int lastdot = 0;
 
@@ -17,7 +16,7 @@ int fqdn_to_qname( char* _source, int _sourcelen, char* _sink ,int _sinklen )
 		_sink[i+1] = _source[i];
 	}
 
-	if( _source[i] ) // _source not terminated
+	if( _source[i] ) // _source not terminated, thus no valid string
 		return -1;
 
 	for (int o = 0; o < i; o++) {
@@ -36,5 +35,27 @@ int fqdn_to_qname( char* _source, int _sourcelen, char* _sink ,int _sinklen )
 
 int qname_to_fqdn( char* _source, int _sourcelen, char* _sink, int _sinklen )
 {
-	return -1;
+	if ( !_sourcelen || !_sinklen ) {
+		return -1;
+	}
+
+	unsigned int next_dot = _source[0] + 1;
+	int i = 1;
+	for(i = 1; i < _sourcelen; i++) {
+		if( i > _sinklen){ //Output too small. Not >= bc sink[i-1] is used
+			return -1;
+		}
+		if ( !_source[i] ) {
+			_sink[i-1] = '\0';
+			break;
+		} else if (i == next_dot) {
+			_sink[i-1]='.';
+			next_dot = _source[i] + i + 1;
+		} else {
+			_sink[i-1] = _source[i];
+		}
+
+	}
+
+	return i-1;
 }
diff --git a/src/dns.h b/src/dns.h
index 9f66367..5d8096e 100644
--- a/src/dns.h
+++ b/src/dns.h
@@ -12,6 +12,8 @@
 int fqdn_to_qname( char* _source, int _sourcelen, char* _sink, int _sinklen );
 
 /**
- * Opposite of fqdn_to_qname()
+ * Convert a QNAME back to a FQDN, reversing fqdn_to_qname( )
+ * returns: length of string in _sink, < 0 on failure
+ * _sink may still be altered in failed attempts, but not terminated.
  * */
 int qname_to_fqdn( char* _source, int _sourcelen, char* _sink, int _sinklen );
-- 
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