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// Copyright (c) 2022, Sylabs Inc. All rights reserved.
// This software is licensed under a 3-clause BSD license. Please consult the
// LICENSE.md file distributed with the sources of this project regarding your
// rights to use or distribute this software.
package client
import (
"archive/tar"
"errors"
"fmt"
"io"
"io/fs"
"path"
"path/filepath"
"strings"
)
type archiver struct {
fs fs.FS
w *tar.Writer
archived map[string]struct{}
}
// newArchiver returns an archiver that will write an archive to w.
func newArchiver(fsys fs.FS, w io.Writer) *archiver {
return &archiver{
fs: fsys,
w: tar.NewWriter(w),
archived: make(map[string]struct{}),
}
}
var errUnsupportedType = errors.New("unsupported file type")
// writeEntry writes the named path from the file system to the archive.
func (ar *archiver) writeEntry(name string) (err error) {
// If entry already exists, skip it.
if _, ok := ar.archived[name]; ok {
return nil
}
defer func() {
if err == nil {
ar.archived[name] = struct{}{}
}
}()
// Get file info.
fi, err := fs.Stat(ar.fs, name)
if err != nil {
return err
}
// Populate TAR header based on file info, and normalize name.
h, err := tar.FileInfoHeader(fi, "")
if err != nil {
return err
}
h.Name = filepath.ToSlash(name)
// Check that we're writing a supported type, and make any necessary adjustments.
switch h.Typeflag {
case tar.TypeReg:
// Nothing to do.
case tar.TypeSymlink:
// Always follow symbolic links.
h.Typeflag = tar.TypeReg
h.Linkname = ""
h.Size = fi.Size()
case tar.TypeDir:
// Normalize name.
if !strings.HasSuffix(h.Name, "/") {
h.Name += "/"
}
default:
return fmt.Errorf("%v: %w (%v)", name, errUnsupportedType, h.Typeflag)
}
// Write TAR header.
if err := ar.w.WriteHeader(h); err != nil {
return err
}
// Write file contents, if applicable.
if h.Typeflag == tar.TypeReg && h.Size > 0 {
f, err := ar.fs.Open(name)
if err != nil {
return err
}
defer f.Close()
if _, err := io.Copy(ar.w, f); err != nil {
return err
}
}
return nil
}
// walkDirFunc returns a WalkDirFunc that writes each path to ar.
func (ar *archiver) walkDirFunc() fs.WalkDirFunc {
return func(path string, d fs.DirEntry, err error) error {
if err != nil {
return err
}
if path == "." {
return nil
}
return ar.writeEntry(path)
}
}
// writeDirAll writes an entry for directory name to the archive, along with any necessary parents.
func (ar *archiver) writeDirAll(name string) error {
if name == "." {
return nil
}
if _, ok := ar.archived[name]; ok {
return nil // Path already archived, no need to recurse.
}
// Recursively create parent(s).
if err := ar.writeDirAll(path.Dir(name)); err != nil {
return err
}
return ar.writeEntry(name)
}
// WriteFiles writes all files matching pattern from the file system to the archive. If the named
// path is a directory, its contents are recursively added using fs.WalkDir.
func (ar *archiver) WriteFiles(pattern string) error {
names, err := fs.Glob(ar.fs, pattern)
if err != nil {
return err
}
if len(names) == 0 {
return fmt.Errorf("%v: %w", pattern, fs.ErrNotExist)
}
for _, name := range names {
// Ensure parent directory exists in archive.
if err := ar.writeDirAll(path.Dir(name)); err != nil {
return err
}
fi, err := fs.Stat(ar.fs, name)
if err != nil {
return err
}
// If name refers to a directory, walk it, adding entries. Otherwise, add a single entry.
if fi.IsDir() {
if err := fs.WalkDir(ar.fs, name, ar.walkDirFunc()); err != nil {
return err
}
} else if err := ar.writeEntry(name); err != nil {
return err
}
}
return nil
}
// Close closes the archive.
func (ar *archiver) Close() error {
return ar.w.Close()
}
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