add untar function to polly

fs/tar.go

@@ -0,0 +1,92 @@
+package fs
+
+import (
+	"archive/tar"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+)
+
+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)
+	madeDir := map[string]bool{}
+
+	for {
+		header, err := tr.Next()
+
+		switch {
+
+		// if no more files are found return
+		case err == io.EOF:
+			return nil
+
+		// return any other error
+		case err != nil:
+			return err
+
+		// if the header is nil, just skip it (not sure how this happens)
+		case header == nil:
+			continue
+		}
+
+		// the target location where the dir/file should be created
+		target := filepath.Join(dst, header.Name)
+		// the following switch could also be done using fi.Mode(), not sure if there
+		// a benefit of using one vs. the other.
+		// fi := header.FileInfo()
+
+		// check the file type
+		switch header.Typeflag {
+
+		// if its a dir and it doesn't exist create it
+		case tar.TypeDir:
+			if err := makeDir(target, madeDir); err != nil {
+				return err
+			}
+
+		// if it's a file create it
+		case tar.TypeReg:
+			if err := makeDir(filepath.Dir(target), madeDir); err != nil {
+				return err
+			}
+
+			f, err := os.OpenFile(target, os.O_CREATE|os.O_RDWR, os.FileMode(header.Mode))
+			if err != nil {
+				fmt.Println("could not open file")
+				return err
+			}
+
+			// copy over contents
+			if _, err := io.Copy(f, tr); err != nil {
+				return err
+			}
+
+			// manually close here after each file operation; defering would cause each file close
+			// to wait until all operations have completed.
+			f.Close()
+		}
+	}
+}
+
+func makeDir(target string, made map[string]bool) error {
+	if made[target] {
+		return nil
+	}
+
+	if _, err := os.Stat(target); err != nil {
+		if err := os.MkdirAll(target, 0755); err != nil {
+			return err
+		}
+	}
+
+	made[target] = true
+	return nil
+}