1// Copyright 2017, OpenCensus Authors
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package tag
16
17import "errors"
18
19const (
20	maxKeyLength = 255
21
22	// valid are restricted to US-ASCII subset (range 0x20 (' ') to 0x7e ('~')).
23	validKeyValueMin = 32
24	validKeyValueMax = 126
25)
26
27var (
28	errInvalidKeyName = errors.New("invalid key name: only ASCII characters accepted; max length must be 255 characters")
29	errInvalidValue   = errors.New("invalid value: only ASCII characters accepted; max length must be 255 characters")
30)
31
32func checkKeyName(name string) bool {
33	if len(name) == 0 {
34		return false
35	}
36	if len(name) > maxKeyLength {
37		return false
38	}
39	return isASCII(name)
40}
41
42func isASCII(s string) bool {
43	for _, c := range s {
44		if (c < validKeyValueMin) || (c > validKeyValueMax) {
45			return false
46		}
47	}
48	return true
49}
50
51func checkValue(v string) bool {
52	if len(v) > maxKeyLength {
53		return false
54	}
55	return isASCII(v)
56}
57