tar/storage: show gzip usage in a test

tar/storage/packer_test.go

@@ -2,6 +2,7 @@ package storage
 
 import (
 	"bytes"
+	"compress/gzip"
 	"io"
 	"testing"
 )
@@ -39,6 +40,9 @@ func TestJsonPackerUnpacker(t *testing.T) {
 		}
 	}()
 
+	// >> packer_test.go:43: uncompressed: 266
+	//t.Errorf("uncompressed: %d", len(b.Bytes()))
+
 	b = bytes.NewBuffer(b.Bytes())
 	entries := Entries{}
 	func() {
@@ -58,5 +62,69 @@ func TestJsonPackerUnpacker(t *testing.T) {
 	if len(entries) != len(e) {
 		t.Errorf("expected %d entries, got %d", len(e), len(entries))
 	}
+}
+
+// you can use a compress Reader/Writer and make nice savings.
+//
+// For these two tests that are using the same set, it the difference of 266
+// bytes uncompressed vs 138 bytes compressed.
+func TestGzip(t *testing.T) {
+	e := []Entry{
+		Entry{
+			Type:    SegmentType,
+			Payload: []byte("how"),
+		},
+		Entry{
+			Type:    SegmentType,
+			Payload: []byte("y'all"),
+		},
+		Entry{
+			Type:    FileType,
+			Name:    "./hurr.txt",
+			Payload: []byte("deadbeef"),
+		},
+		Entry{
+			Type:    SegmentType,
+			Payload: []byte("doin"),
+		},
+	}
+
+	buf := []byte{}
+	b := bytes.NewBuffer(buf)
+	gzW := gzip.NewWriter(b)
+	jp := NewJsonPacker(gzW)
+	for i := range e {
+		if _, err := jp.AddEntry(e[i]); err != nil {
+			t.Error(err)
+		}
+	}
+	gzW.Close()
+
+	// >> packer_test.go:99: compressed: 138
+	//t.Errorf("compressed: %d", len(b.Bytes()))
+
+	b = bytes.NewBuffer(b.Bytes())
+	gzR, err := gzip.NewReader(b)
+	if err != nil {
+		t.Fatal(err)
+	}
+	entries := Entries{}
+	func() {
+		jup := NewJsonUnpacker(gzR)
+		for {
+			entry, err := jup.Next()
+			if err != nil {
+				if err == io.EOF {
+					break
+				}
+				t.Error(err)
+			}
+			entries = append(entries, *entry)
+			t.Logf("got %#v", entry)
+		}
+	}()
+	if len(entries) != len(e) {
+		t.Errorf("expected %d entries, got %d", len(e), len(entries))
+	}
 
 }