libgo/misc/cgo/testso/overlaydir_test.go

   1 // Copyright 2019 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 so_test
   6
   7 import (
   8         "io"
   9         "os"
  10         "path/filepath"
  11         "strings"
  12 )
  13
  14 // overlayDir makes a minimal-overhead copy of srcRoot in which new files may be added.
  15 //
  16 // TODO: Once we no longer need to support the misc module in GOPATH mode,
  17 // factor this function out into a package to reduce duplication.
  18 func overlayDir(dstRoot, srcRoot string) error {
  19         dstRoot = filepath.Clean(dstRoot)
  20         if err := os.MkdirAll(dstRoot, 0777); err != nil {
  21                 return err
  22         }
  23
  24         srcRoot, err := filepath.Abs(srcRoot)
  25         if err != nil {
  26                 return err
  27         }
  28
  29         return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
  30                 if err != nil || srcPath == srcRoot {
  31                         return err
  32                 }
  33
  34                 suffix := strings.TrimPrefix(srcPath, srcRoot)
  35                 for len(suffix) > 0 && suffix[0] == filepath.Separator {
  36                         suffix = suffix[1:]
  37                 }
  38                 dstPath := filepath.Join(dstRoot, suffix)
  39
  40                 perm := info.Mode() & os.ModePerm
  41                 if info.Mode()&os.ModeSymlink != 0 {
  42                         info, err = os.Stat(srcPath)
  43                         if err != nil {
  44                                 return err
  45                         }
  46                         perm = info.Mode() & os.ModePerm
  47                 }
  48
  49                 // Always copy directories (don't symlink them).
  50                 // If we add a file in the overlay, we don't want to add it in the original.
  51                 if info.IsDir() {
  52                         return os.MkdirAll(dstPath, perm|0200)
  53                 }
  54
  55                 // If the OS supports symlinks, use them instead of copying bytes.
  56                 if err := os.Symlink(srcPath, dstPath); err == nil {
  57                         return nil
  58                 }
  59
  60                 // Otherwise, copy the bytes.
  61                 src, err := os.Open(srcPath)
  62                 if err != nil {
  63                         return err
  64                 }
  65                 defer src.Close()
  66
  67                 dst, err := os.OpenFile(dstPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, perm)
  68                 if err != nil {
  69                         return err
  70                 }
  71
  72                 _, err = io.Copy(dst, src)
  73                 if closeErr := dst.Close(); err == nil {
  74                         err = closeErr
  75                 }
  76                 return err
  77         })
  78 }