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// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package toolchain
import (
"io/fs"
"os"
"path/filepath"
"strings"
"sync"
"cmd/go/internal/gover"
)
// pathExts is a cached PATHEXT list.
var pathExts struct {
once sync.Once
list []string
}
func initPathExts() {
var exts []string
x := os.Getenv(`PATHEXT`)
if x != "" {
for _, e := range strings.Split(strings.ToLower(x), `;`) {
if e == "" {
continue
}
if e[0] != '.' {
e = "." + e
}
exts = append(exts, e)
}
} else {
exts = []string{".com", ".exe", ".bat", ".cmd"}
}
pathExts.list = exts
}
// pathDirs returns the directories in the system search path.
func pathDirs() []string {
return filepath.SplitList(os.Getenv("PATH"))
}
// pathVersion returns the Go version implemented by the file
// described by de and info in directory dir.
// The analysis only uses the name itself; it does not run the program.
func pathVersion(dir string, de fs.DirEntry, info fs.FileInfo) (string, bool) {
pathExts.once.Do(initPathExts)
name, _, ok := cutExt(de.Name(), pathExts.list)
if !ok {
return "", false
}
v := gover.FromToolchain(name)
if v == "" {
return "", false
}
return v, true
}
// cutExt looks for any of the known extensions at the end of file.
// If one is found, cutExt returns the file name with the extension trimmed,
// the extension itself, and true to signal that an extension was found.
// Otherwise cutExt returns file, "", false.
func cutExt(file string, exts []string) (name, ext string, found bool) {
i := strings.LastIndex(file, ".")
if i < 0 {
return file, "", false
}
for _, x := range exts {
if strings.EqualFold(file[i:], x) {
return file[:i], file[i:], true
}
}
return file, "", false
}
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