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// Copyright 2017 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 cache
import (
"fmt"
"io/ioutil"
"os"
"path/filepath"
"runtime"
"sync"
)
// Default returns the default cache to use, or nil if no cache should be used.
func Default() *Cache {
defaultOnce.Do(initDefaultCache)
return defaultCache
}
var (
defaultOnce sync.Once
defaultCache *Cache
)
// cacheREADME is a message stored in a README in the cache directory.
// Because the cache lives outside the normal Go trees, we leave the
// README as a courtesy to explain where it came from.
const cacheREADME = `This directory holds cached build artifacts from the Go build system.
Run "go clean -cache" if the directory is getting too large.
See golang.org to learn more about Go.
`
// initDefaultCache does the work of finding the default cache
// the first time Default is called.
func initDefaultCache() {
dir := DefaultDir()
if dir == "off" {
return
}
if err := os.MkdirAll(dir, 0777); err != nil {
fmt.Fprintf(os.Stderr, "go: disabling cache (%s) due to initialization failure: %s\n", dir, err)
return
}
if _, err := os.Stat(filepath.Join(dir, "README")); err != nil {
// Best effort.
ioutil.WriteFile(filepath.Join(dir, "README"), []byte(cacheREADME), 0666)
}
c, err := Open(dir)
if err != nil {
fmt.Fprintf(os.Stderr, "go: disabling cache (%s) due to initialization failure: %s\n", dir, err)
return
}
defaultCache = c
}
// DefaultDir returns the effective GOCACHE setting.
// It returns "off" if the cache is disabled.
func DefaultDir() string {
dir := os.Getenv("GOCACHE")
if dir != "" {
return dir
}
// Compute default location.
// TODO(rsc): This code belongs somewhere else,
// like maybe ioutil.CacheDir or os.CacheDir.
switch runtime.GOOS {
case "windows":
dir = os.Getenv("LocalAppData")
if dir == "" {
// Fall back to %AppData%, the old name of
// %LocalAppData% on Windows XP.
dir = os.Getenv("AppData")
}
if dir == "" {
return "off"
}
case "darwin":
dir = os.Getenv("HOME")
if dir == "" {
return "off"
}
dir += "/Library/Caches"
case "plan9":
dir = os.Getenv("home")
if dir == "" {
return "off"
}
// Plan 9 has no established per-user cache directory,
// but $home/lib/xyz is the usual equivalent of $HOME/.xyz on Unix.
dir += "/lib/cache"
default: // Unix
// https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
dir = os.Getenv("XDG_CACHE_HOME")
if dir == "" {
dir = os.Getenv("HOME")
if dir == "" {
return "off"
}
dir += "/.cache"
}
}
return filepath.Join(dir, "go-build")
}
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