github.com/goproxy0/go@v0.0.0-20171111080102-49cc0c489d2c/src/cmd/go/internal/cache/default.go (about)

     1  // Copyright 2017 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package cache
     6  
     7  import (
     8  	"cmd/go/internal/base"
     9  	"io/ioutil"
    10  	"os"
    11  	"path/filepath"
    12  	"runtime"
    13  	"sync"
    14  )
    15  
    16  // Default returns the default cache to use, or nil if no cache should be used.
    17  func Default() *Cache {
    18  	defaultOnce.Do(initDefaultCache)
    19  	return defaultCache
    20  }
    21  
    22  var (
    23  	defaultOnce  sync.Once
    24  	defaultCache *Cache
    25  )
    26  
    27  // cacheREADME is a message stored in a README in the cache directory.
    28  // Because the cache lives outside the normal Go trees, we leave the
    29  // README as a courtesy to explain where it came from.
    30  const cacheREADME = `This directory holds cached build artifacts from the Go build system.
    31  Run "go clean -cache" if the directory is getting too large.
    32  See golang.org to learn more about Go.
    33  `
    34  
    35  // initDefaultCache does the work of finding the default cache
    36  // the first time Default is called.
    37  func initDefaultCache() {
    38  	dir := DefaultDir()
    39  	if dir == "off" {
    40  		return
    41  	}
    42  	if err := os.MkdirAll(dir, 0777); err != nil {
    43  		base.Fatalf("initializing cache in $GOCACHE: %s", err)
    44  	}
    45  	if _, err := os.Stat(filepath.Join(dir, "README")); err != nil {
    46  		// Best effort.
    47  		ioutil.WriteFile(filepath.Join(dir, "README"), []byte(cacheREADME), 0666)
    48  	}
    49  
    50  	c, err := Open(dir)
    51  	if err != nil {
    52  		base.Fatalf("initializing cache in $GOCACHE: %s", err)
    53  	}
    54  	defaultCache = c
    55  }
    56  
    57  // DefaultDir returns the effective GOCACHE setting.
    58  // It returns "off" if the cache is disabled.
    59  func DefaultDir() string {
    60  	dir := os.Getenv("GOCACHE")
    61  	if dir != "" {
    62  		return dir
    63  	}
    64  
    65  	// Compute default location.
    66  	// TODO(rsc): This code belongs somewhere else,
    67  	// like maybe ioutil.CacheDir or os.CacheDir.
    68  	switch runtime.GOOS {
    69  	case "windows":
    70  		dir = os.Getenv("LocalAppData")
    71  
    72  	case "darwin":
    73  		dir = os.Getenv("HOME")
    74  		if dir == "" {
    75  			return "off"
    76  		}
    77  		dir += "/Library/Caches"
    78  
    79  	case "plan9":
    80  		dir = os.Getenv("home")
    81  		if dir == "" {
    82  			return "off"
    83  		}
    84  		// Plan 9 has no established per-user cache directory,
    85  		// but $home/lib/xyz is the usual equivalent of $HOME/.xyz on Unix.
    86  		dir += "/lib/cache"
    87  
    88  	default: // Unix
    89  		// https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
    90  		dir = os.Getenv("XDG_CACHE_HOME")
    91  		if dir == "" {
    92  			dir = os.Getenv("HOME")
    93  			if dir == "" {
    94  				return "off"
    95  			}
    96  			dir += "/.cache"
    97  		}
    98  	}
    99  	return filepath.Join(dir, "go-build")
   100  }