Begin work on reading mothballs

mothball.go

@@ -0,0 +1,52 @@
+package mothball
+
+import (
+	"archive/zip"
+	"os"
+	"time"
+)
+
+type Mothball struct {
+	zf *zipfile.File,
+	filename string,
+	mtime time.Time,
+}
+
+func Open(filename string) (*Mothball, error) {
+	var m Mothball
+	
+	m.filename = filename
+	
+	err := m.Refresh()
+	if err != nil {
+		return err
+	}
+
+	return &m
+}
+
+func (m Mothball) Close() (error) {
+	return m.zf.Close()
+}
+
+func (m Mothball) Refresh() (error) {
+	mtime, err := os.Stat(m.filename)
+	if err != nil {
+		return err
+	}
+	
+	if mtime == m.mtime {
+		return nil
+	}
+	
+	zf, err := zip.OpenReader(m.filename)
+	if err != nil {
+		return err
+	}
+	
+	m.zf.Close()
+	m.zf = zf
+	m.mtime = mtime
+}
+
+func (m Mothball)