Add EqualFold function on AttributeTypeAndValue.

Since v3 ldap we have case insensitive search in parallel to a case sensitive search:

I would like to propose to add an EqualFold function in parallel to Equal function in dn.go on AttributeTypeAndValue.

So we can not only search in case sensitive but also compare RDNs.

Author: zerodayz

dn.go

@@ -205,3 +205,50 @@ func (r *RelativeDN) hasAllAttributes(attrs []*AttributeTypeAndValue) bool {
 func (a *AttributeTypeAndValue) Equal(other *AttributeTypeAndValue) bool {
 	return strings.EqualFold(a.Type, other.Type) && a.Value == other.Value
 }
+
+// AncestorOfFold returns true if the other DN consists of at least one RDN followed by all the RDNs of the current DN.
+// Case of the attribute type and value is not significant
+func (d *DN) AncestorOfFold(other *DN) bool {
+	if len(d.RDNs) >= len(other.RDNs) {
+		return false
+	}
+	// Take the last `len(d.RDNs)` RDNs from the other DN to compare against
+	otherRDNs := other.RDNs[len(other.RDNs)-len(d.RDNs):]
+	for i := range d.RDNs {
+		if !d.RDNs[i].EqualFold(otherRDNs[i]) {
+			return false
+		}
+	}
+	return true
+}
+
+// Equal returns true if the RelativeDNs are equal as defined by rfc4517 4.2.15 (distinguishedNameMatch).
+// Case of the attribute type is not significant
+func (r *RelativeDN) EqualFold(other *RelativeDN) bool {
+	if len(r.Attributes) != len(other.Attributes) {
+		return false
+	}
+	return r.hasAllAttributesFold(other.Attributes) && other.hasAllAttributesFold(r.Attributes)
+}
+
+func (r *RelativeDN) hasAllAttributesFold(attrs []*AttributeTypeAndValue) bool {
+	for _, attr := range attrs {
+		found := false
+		for _, myattr := range r.Attributes {
+			if myattr.EqualFold(attr) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return false
+		}
+	}
+	return true
+}
+
+// EqualFold returns true if the AttributeTypeAndValue is equivalent to the specified AttributeTypeAndValue
+// Case of the attribute type and value is not significant
+func (a *AttributeTypeAndValue) EqualFold(other *AttributeTypeAndValue) bool {
+	return strings.EqualFold(a.Type, other.Type) && strings.EqualFold(a.Value, other.Value)
+}