Add validation primitives to util

Part 2 in a series of changes towards data validation.

pkg/util/validation.go

@@ -0,0 +1,53 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"regexp"
+)
+
+var dnsLabelFmt string = "[a-z0-9]([-a-z0-9]*[a-z0-9])?"
+var dnsLabelRegexp *regexp.Regexp = regexp.MustCompile("^" + dnsLabelFmt + "$")
+
+// IsDNSLabel tests for a string that conforms to the definition of a label in
+// DNS (RFC 1035/1123).  This checks the format, but not the length.
+func IsDNSLabel(value string) bool {
+	return dnsLabelRegexp.MatchString(value)
+}
+
+var dnsSubdomainFmt string = dnsLabelFmt + "(\\." + dnsLabelFmt + ")*"
+var dnsSubdomainRegexp *regexp.Regexp = regexp.MustCompile("^" + dnsSubdomainFmt + "$")
+
+// IsDNSSubdomain tests for a string that conforms to the definition of a
+// subdomain in DNS (RFC 1035/1123).  This checks the format, but not the length.
+func IsDNSSubdomain(value string) bool {
+	return dnsSubdomainRegexp.MatchString(value)
+}
+
+var cIdentifierFmt string = "[A-Za-z_][A-Za-z0-9_]*"
+var cIdentifierRegexp *regexp.Regexp = regexp.MustCompile("^" + cIdentifierFmt + "$")
+
+// IsCIdentifier tests for a string that conforms the definition of an identifier
+// in C. This checks the format, but not the length.
+func IsCIdentifier(value string) bool {
+	return cIdentifierRegexp.MatchString(value)
+}
+
+// IsValidPortNum tests that the argument is a valid, non-zero port number.
+func IsValidPortNum(port int) bool {
+	return 0 < port && port < 65536
+}