github.com/sirkon/goproxy@v1.4.8/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  	"fmt"
     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, showWarnings := defaultDir()
    39  	if dir == "off" {
    40  		return
    41  	}
    42  	if err := os.MkdirAll(dir, 0777); err != nil {
    43  		if showWarnings {
    44  			fmt.Fprintf(os.Stderr, "go: disabling cache (%s) due to initialization failure: %s\n", dir, err)
    45  		}
    46  		return
    47  	}
    48  	if _, err := os.Stat(filepath.Join(dir, "README")); err != nil {
    49  		// Best effort.
    50  		ioutil.WriteFile(filepath.Join(dir, "README"), []byte(cacheREADME), 0666)
    51  	}
    52  
    53  	c, err := Open(dir)
    54  	if err != nil {
    55  		if showWarnings {
    56  			fmt.Fprintf(os.Stderr, "go: disabling cache (%s) due to initialization failure: %s\n", dir, err)
    57  		}
    58  		return
    59  	}
    60  	defaultCache = c
    61  }
    62  
    63  // DefaultDir returns the effective GOCACHE setting.
    64  // It returns "off" if the cache is disabled.
    65  func DefaultDir() string {
    66  	dir, _ := defaultDir()
    67  	return dir
    68  }
    69  
    70  // defaultDir returns the effective GOCACHE setting.
    71  // It returns "off" if the cache is disabled.
    72  // The second return value reports whether warnings should
    73  // be shown if the cache fails to initialize.
    74  func defaultDir() (string, bool) {
    75  	dir := os.Getenv("GOCACHE")
    76  	if dir != "" {
    77  		return dir, true
    78  	}
    79  
    80  	// Compute default location.
    81  	// TODO(rsc): This code belongs somewhere else,
    82  	// like maybe ioutil.CacheDir or os.CacheDir.
    83  	showWarnings := true
    84  	switch runtime.GOOS {
    85  	case "windows":
    86  		dir = os.Getenv("LocalAppData")
    87  		if dir == "" {
    88  			// Fall back to %AppData%, the old name of
    89  			// %LocalAppData% on Windows XP.
    90  			dir = os.Getenv("AppData")
    91  		}
    92  		if dir == "" {
    93  			return "off", true
    94  		}
    95  
    96  	case "darwin":
    97  		dir = os.Getenv("HOME")
    98  		if dir == "" {
    99  			return "off", true
   100  		}
   101  		dir += "/Library/Caches"
   102  
   103  	case "plan9":
   104  		dir = os.Getenv("home")
   105  		if dir == "" {
   106  			return "off", true
   107  		}
   108  		// Plan 9 has no established per-user cache directory,
   109  		// but $home/lib/xyz is the usual equivalent of $HOME/.xyz on Unix.
   110  		dir += "/lib/cache"
   111  
   112  	default: // Unix
   113  		// https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
   114  		dir = os.Getenv("XDG_CACHE_HOME")
   115  		if dir == "" {
   116  			dir = os.Getenv("HOME")
   117  			if dir == "" {
   118  				return "off", true
   119  			}
   120  			if dir == "/" {
   121  				// probably docker run with -u flag
   122  				// https://golang.org/issue/26280
   123  				showWarnings = false
   124  			}
   125  			dir += "/.cache"
   126  		}
   127  	}
   128  	return filepath.Join(dir, "go-build"), showWarnings
   129  }