1 // Copyright 2023 Google LLC
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 15 package externalaccount
16 17 import (
18 "runtime"
19 "strings"
20 "unicode"
21 )
22 23 var (
24 // version is a package internal global variable for testing purposes.
25 version = runtime.Version
26 )
27 28 // versionUnknown is only used when the runtime version cannot be determined.
29 const versionUnknown = "UNKNOWN"
30 31 // goVersion returns a Go runtime version derived from the runtime environment
32 // that is modified to be suitable for reporting in a header, meaning it has no
33 // whitespace. If it is unable to determine the Go runtime version, it returns
34 // versionUnknown.
35 func goVersion() string {
36 const develPrefix = "devel +"
37 38 s := version()
39 if strings.HasPrefix(s, develPrefix) {
40 s = s[len(develPrefix):]
41 if p := strings.IndexFunc(s, unicode.IsSpace); p >= 0 {
42 s = s[:p]
43 }
44 return s
45 } else if p := strings.IndexFunc(s, unicode.IsSpace); p >= 0 {
46 s = s[:p]
47 }
48 49 notSemverRune := func(r rune) bool {
50 return !strings.ContainsRune("0123456789.", r)
51 }
52 53 if strings.HasPrefix(s, "go1") {
54 s = s[2:]
55 var prerelease string
56 if p := strings.IndexFunc(s, notSemverRune); p >= 0 {
57 s, prerelease = s[:p], s[p:]
58 }
59 if strings.HasSuffix(s, ".") {
60 s += "0"
61 } else if strings.Count(s, ".") < 2 {
62 s += ".0"
63 }
64 if prerelease != "" {
65 // Some release candidates already have a dash in them.
66 if !strings.HasPrefix(prerelease, "-") {
67 prerelease = "-" + prerelease
68 }
69 s += prerelease
70 }
71 return s
72 }
73 return versionUnknown
74 }
75