dotcloud/docker

package remotecontext // import "github.com/docker/docker/builder/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) {
    var link string
    if fi.Mode()&os.ModeSymlink != 0 {
        var err error
        link, err = os.Readlink(path)
        if err != nil {
            return nil, err
        }
    }
    hdr, err := archive.FileInfoHeader(name, fi, link)
    if err != nil {
        return nil, err
    }
    if err := archive.ReadSecurityXattrToTarHeader(path, hdr); 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)
}