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package pkg
import (
"crypto/sha512"
"encoding/gob"
"io"
"io/fs"
"os"
"hakurei.app/container/check"
)
// FlatEntry is the representation of a directory entry via [Flatten].
type FlatEntry struct {
Name string // base name of the file
Mode fs.FileMode // file mode bits
Data []byte // file content or symlink destination
}
// Flatten writes a deterministic representation of the contents of fsys to w.
// The resulting data can be hashed to produce a deterministic checksum for the
// directory.
func Flatten(fsys fs.FS, root string, w io.Writer) error {
e := gob.NewEncoder(w)
return fs.WalkDir(fsys, root, func(path string, d fs.DirEntry, err error) error {
if err != nil {
return err
}
var fi fs.FileInfo
fi, err = d.Info()
if err != nil {
return err
}
ent := FlatEntry{
Name: fi.Name(),
Mode: fi.Mode(),
}
if ent.Mode.IsRegular() {
if ent.Data, err = fs.ReadFile(fsys, path); err != nil {
return err
}
} else if ent.Mode&fs.ModeSymlink != 0 {
var newpath string
if newpath, err = fs.ReadLink(fsys, path); err != nil {
return err
}
ent.Data = []byte(newpath)
}
return e.Encode(&ent)
})
}
// HashFS returns a checksum produced by hashing the result of [Flatten].
func HashFS(fsys fs.FS, root string) (Checksum, error) {
h := sha512.New384()
if err := Flatten(fsys, root, h); err != nil {
return Checksum{}, err
}
return (Checksum)(h.Sum(nil)), nil
}
// HashDir returns a checksum produced by hashing the result of [Flatten].
func HashDir(pathname *check.Absolute) (Checksum, error) {
return HashFS(os.DirFS(pathname.String()), ".")
}
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