216 lines
5.3 KiB
Go
216 lines
5.3 KiB
Go
package slug
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import (
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"archive/tar"
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"compress/gzip"
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"fmt"
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"io"
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"os"
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"path/filepath"
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)
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// Meta provides detailed information about a slug.
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type Meta struct {
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// The list of files contained in the slug.
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Files []string
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// Total size of the slug in bytes.
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Size int64
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}
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// Pack creates a slug from a directory src, and writes the new
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// slug to w. Returns metadata about the slug and any error.
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func Pack(src string, w io.Writer) (*Meta, error) {
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// Gzip compress all the output data
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gzipW := gzip.NewWriter(w)
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// Tar the file contents
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tarW := tar.NewWriter(gzipW)
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// Track the metadata details as we go.
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meta := &Meta{}
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// Walk the tree of files
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err := filepath.Walk(src, func(path string, info os.FileInfo, err error) error {
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if err != nil {
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return err
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}
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// Check the file type and if we need to write the body
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keepFile, writeBody := checkFileMode(info.Mode())
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if !keepFile {
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return nil
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}
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// Get the relative path from the unpack directory
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subpath, err := filepath.Rel(src, path)
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if err != nil {
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return fmt.Errorf("Failed to get relative path for file %q: %v", path, err)
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}
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if subpath == "." {
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return nil
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}
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// Read the symlink target. We don't track the error because
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// it doesn't matter if there is an error.
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target, _ := os.Readlink(path)
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// Build the file header for the tar entry
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header, err := tar.FileInfoHeader(info, target)
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if err != nil {
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return fmt.Errorf("Failed creating archive header for file %q: %v", path, err)
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}
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// Modify the header to properly be the full subpath
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header.Name = subpath
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if info.IsDir() {
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header.Name += "/"
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}
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// Write the header first to the archive.
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if err := tarW.WriteHeader(header); err != nil {
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return fmt.Errorf("Failed writing archive header for file %q: %v", path, err)
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}
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// Account for the file in the list
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meta.Files = append(meta.Files, header.Name)
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// Skip writing file data for certain file types (above).
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if !writeBody {
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return nil
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}
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// Add the size since we are going to write the body.
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meta.Size += info.Size()
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f, err := os.Open(path)
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if err != nil {
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return fmt.Errorf("Failed opening file %q for archiving: %v", path, err)
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}
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defer f.Close()
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if _, err = io.Copy(tarW, f); err != nil {
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return fmt.Errorf("Failed copying file %q to archive: %v", path, err)
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}
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return nil
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})
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if err != nil {
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return nil, err
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}
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// Flush the tar writer
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if err := tarW.Close(); err != nil {
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return nil, fmt.Errorf("Failed to close the tar archive: %v", err)
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}
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// Flush the gzip writer
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if err := gzipW.Close(); err != nil {
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return nil, fmt.Errorf("Failed to close the gzip writer: %v", err)
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}
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return meta, nil
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}
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// Unpack is used to read and extract the contents of a slug to
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// directory dst. Returns any error.
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func Unpack(r io.Reader, dst string) error {
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// Decompress as we read
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uncompressed, err := gzip.NewReader(r)
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if err != nil {
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return fmt.Errorf("Failed to uncompress slug: %v", err)
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}
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// Untar as we read
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untar := tar.NewReader(uncompressed)
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// Unpackage all the contents into the directory
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for {
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header, err := untar.Next()
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if err == io.EOF {
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break
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}
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if err != nil {
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return fmt.Errorf("Failed to untar slug: %v", err)
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}
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// Get rid of absolute paths
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path := header.Name
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if path[0] == '/' {
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path = path[1:]
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}
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path = filepath.Join(dst, path)
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// Make the directories to the path
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dir := filepath.Dir(path)
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if err := os.MkdirAll(dir, 0755); err != nil {
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return fmt.Errorf("Failed to create directory %q: %v", dir, err)
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}
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// If we have a symlink, just link it.
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if header.Typeflag == tar.TypeSymlink {
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if err := os.Symlink(header.Linkname, path); err != nil {
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return fmt.Errorf("Failed creating symlink %q => %q: %v",
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path, header.Linkname, err)
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}
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continue
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}
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// Only unpack regular files from this point on
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if header.Typeflag == tar.TypeDir {
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continue
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} else if header.Typeflag != tar.TypeReg && header.Typeflag != tar.TypeRegA {
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return fmt.Errorf("Failed creating %q: unsupported type %c", path,
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header.Typeflag)
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}
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// Open a handle to the destination
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fh, err := os.Create(path)
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if err != nil {
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// This mimics tar's behavior wrt the tar file containing duplicate files
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// and it allowing later ones to clobber earlier ones even if the file
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// has perms that don't allow overwriting
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if os.IsPermission(err) {
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os.Chmod(path, 0600)
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fh, err = os.Create(path)
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}
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if err != nil {
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return fmt.Errorf("Failed creating file %q: %v", path, err)
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}
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}
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// Copy the contents
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_, err = io.Copy(fh, untar)
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fh.Close()
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if err != nil {
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return fmt.Errorf("Failed to copy slug file %q: %v", path, err)
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}
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// Restore the file mode. We have to do this after writing the file,
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// since it is possible we have a read-only mode.
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mode := header.FileInfo().Mode()
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if err := os.Chmod(path, mode); err != nil {
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return fmt.Errorf("Failed setting permissions on %q: %v", path, err)
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}
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}
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return nil
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}
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// checkFileMode is used to examine an os.FileMode and determine if it should
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// be included in the archive, and if it has a data body which needs writing.
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func checkFileMode(m os.FileMode) (keep, body bool) {
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switch {
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case m.IsRegular():
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return true, true
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case m.IsDir():
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return true, false
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case m&os.ModeSymlink != 0:
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return true, false
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}
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return false, false
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}
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