util.go

package build

import (
	"archive/tar"
	"compress/gzip"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
)

// getTrueDirectory converts given filepath to host-based filepath if applicable
// - Docker commands are sent to the mounted Docker socket and hence are
// executed on the host, using the host's filepaths, which means Docker client
// commands must use this function when dealing with paths
func getTrueDirectory(path string) string {
	return strings.Replace(path, "/app/host", os.Getenv("HOME"), 1)
}

// buildTar takes a source and variable writers and walks 'source' writing each file
// found to the tar writer; the purpose for accepting multiple writers is to allow
// for multiple outputs (for example a file, or md5 hash)
// Sourced from https://gist.github.com/sdomino/e6bc0c98f87843bc26bb#file-targz-go
func buildTar(dir string, outputs ...io.Writer) error {

	// ensure the src actually exists before trying to tar it
	if _, err := os.Stat(dir); err != nil {
		return fmt.Errorf("Unable to tar files - %v", err.Error())
	}

	mw := io.MultiWriter(outputs...)

	gzw := gzip.NewWriter(mw)
	defer gzw.Close()

	tw := tar.NewWriter(gzw)
	defer tw.Close()

	return filepath.Walk(dir, func(file string, fi os.FileInfo, err error) error {
		// return on any error
		if err != nil {
			return err
		}

		// create a new dir/file header
		header, err := tar.FileInfoHeader(fi, fi.Name())
		if err != nil {
			return err
		}

		// update the name to correctly reflect the desired destination when untaring
		header.Name = strings.TrimPrefix(strings.Replace(file, dir, "", -1), string(filepath.Separator))

		// write the header
		if err := tw.WriteHeader(header); err != nil {
			return err
		}

		// return on non-regular files
		if !fi.Mode().IsRegular() {
			return nil
		}

		// open files for taring
		f, err := os.Open(file)
		if err != nil {
			return err
		}
		defer f.Close()

		// copy file data into tar writer
		_, err = io.Copy(tw, f)
		return err
	})
}