82 lines
1.9 KiB
Go
82 lines
1.9 KiB
Go
// Copyright 2019 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package shared_test
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import (
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"io"
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"os"
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"path/filepath"
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"strings"
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)
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// overlayDir makes a minimal-overhead copy of srcRoot in which new files may be added.
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//
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// TODO: Once we no longer need to support the misc module in GOPATH mode,
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// factor this function out into a package to reduce duplication.
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func overlayDir(dstRoot, srcRoot string) error {
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dstRoot = filepath.Clean(dstRoot)
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if err := os.MkdirAll(dstRoot, 0777); err != nil {
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return err
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}
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symBase, err := filepath.Rel(srcRoot, dstRoot)
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if err != nil {
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symBase, err = filepath.Abs(srcRoot)
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if err != nil {
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return err
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}
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}
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return filepath.Walk(srcRoot, func(srcPath string, info os.FileInfo, err error) error {
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if err != nil || srcPath == srcRoot {
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return err
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}
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suffix := strings.TrimPrefix(srcPath, srcRoot)
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for len(suffix) > 0 && suffix[0] == filepath.Separator {
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suffix = suffix[1:]
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}
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dstPath := filepath.Join(dstRoot, suffix)
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perm := info.Mode() & os.ModePerm
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if info.Mode()&os.ModeSymlink != 0 {
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info, err = os.Stat(srcPath)
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if err != nil {
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return err
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}
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perm = info.Mode() & os.ModePerm
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}
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// Always copy directories (don't symlink them).
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// If we add a file in the overlay, we don't want to add it in the original.
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if info.IsDir() {
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return os.Mkdir(dstPath, perm)
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}
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// If the OS supports symlinks, use them instead of copying bytes.
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if err := os.Symlink(filepath.Join(symBase, suffix), dstPath); err == nil {
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return nil
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}
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// Otherwise, copy the bytes.
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src, err := os.Open(srcPath)
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if err != nil {
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return err
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}
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defer src.Close()
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dst, err := os.OpenFile(dstPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, perm)
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if err != nil {
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return err
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}
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_, err = io.Copy(dst, src)
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if closeErr := dst.Close(); err == nil {
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err = closeErr
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}
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return err
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})
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}
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