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moby--moby/builder/remotecontext/filehash.go

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package remotecontext
import (
"archive/tar"
"crypto/sha256"
"hash"
"os"
"github.com/docker/docker/pkg/archive"
"github.com/docker/docker/pkg/tarsum"
)
// NewFileHash returns new hash that is used for the builder cache keys
func NewFileHash(path, name string, fi os.FileInfo) (hash.Hash, error) {
hdr, err := archive.FileInfoHeader(path, name, fi)
if err != nil {
return nil, err
}
tsh := &tarsumHash{hdr: hdr, Hash: sha256.New()}
tsh.Reset() // initialize header
return tsh, nil
}
type tarsumHash struct {
hash.Hash
hdr *tar.Header
}
// Reset resets the Hash to its initial state.
func (tsh *tarsumHash) Reset() {
// comply with hash.Hash and reset to the state hash had before any writes
tsh.Hash.Reset()
tarsum.WriteV1Header(tsh.hdr, tsh.Hash)
}