wip: needs tests

cache/tar.go

@@ -0,0 +1,115 @@
+package cache
+
+import (
+	"archive/tar"
+	"compress/gzip"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// Tar 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)
+func Tar(src string, writers ...io.Writer) error {
+	if _, err := os.Stat(src); err != nil {
+		return fmt.Errorf("unable to tar files - %v", err.Error())
+	}
+
+	mw := io.MultiWriter(writers...)
+
+	gzw := gzip.NewWriter(mw)
+	defer gzw.Close()
+
+	tw := tar.NewWriter(gzw)
+	defer tw.Close()
+
+	// walk path
+	return filepath.Walk(src, func(file string, fi os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		if !fi.Mode().IsRegular() {
+			return nil
+		}
+
+		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, src, "", -1), string(filepath.Separator))
+
+		if err := tw.WriteHeader(header); err != nil {
+			return err
+		}
+
+		f, err := os.Open(file)
+		if err != nil {
+			return err
+		}
+
+		if _, err := io.Copy(tw, f); err != nil {
+			f.Close()
+			return err
+		}
+
+		f.Close()
+
+		return nil
+	})
+}
+
+// Untar takes a destination path and a reader; a tar reader loops over the tarfile
+// creating the file structure at 'dst' along the way, and writing any files
+func Untar(dst string, r io.Reader) error {
+
+	gzr, err := gzip.NewReader(r)
+	if err != nil {
+		return err
+	}
+	defer gzr.Close()
+
+	tr := tar.NewReader(gzr)
+
+	for {
+		header, err := tr.Next()
+
+		if errors.Is(err, io.EOF) || header == nil {
+			break
+		}
+		if err != nil {
+			return err
+		}
+
+		target := filepath.Join(dst, header.Name)
+
+		switch header.Typeflag {
+
+		// if its a dir and it doesn't exist create it
+		case tar.TypeDir:
+			if _, err := os.Stat(target); err != nil {
+				if err := os.MkdirAll(target, 0755); err != nil {
+					return err
+				}
+			}
+
+		// if it's a file create it
+		case tar.TypeReg:
+			f, err := os.OpenFile(target, os.O_CREATE|os.O_RDWR, os.FileMode(header.Mode))
+			if err != nil {
+				return err
+			}
+			if _, err := io.Copy(f, tr); err != nil {
+				return err
+			}
+			f.Close()
+		}
+	}
+	return nil
+}