Merged in meta-from-map (pull request #380)

Meta from map

Approved-by: Saxon Milton <saxon.milton@gmail.com>

container/mts/meta/meta.go

@@ -90,6 +90,17 @@ func NewWith(data [][2]string) *Data {
 	return m
 }
 
+// NewFromMap creates a meta.Data from a map.
+func NewFromMap(data map[string]string) *Data {
+	m := New()
+	m.order = make([]string, 0, len(data))
+	for k, v := range data {
+		m.data[k] = v
+		m.order = append(m.order, k)
+	}
+	return m
+}
+
 // Add adds metadata with key and val.
 func (m *Data) Add(key, val string) {
 	m.mu.Lock()
@@ -167,6 +178,23 @@ func (m *Data) Encode() []byte {
 	return m.enc
 }
 
+// EncodeAsString takes the meta data map and encodes into a string with the data in
+// TSV format. Unlike encode, the header with version and length of data is not
+// included. This method is used for storing metadata in the store on vidgrind.
+func (m *Data) EncodeAsString() string {
+	// Iterate over map and append entries, only adding tab if we're not on the
+	// last entry.
+	var str string
+	for i, k := range m.order {
+		v := m.data[k]
+		str += k + "=" + v
+		if i+1 < len(m.data) {
+			str += "\t"
+		}
+	}
+	return str
+}
+
 // Keys returns all keys in a slice of metadata d.
 func Keys(d []byte) ([]string, error) {
 	m, err := GetAll(d)
@@ -227,9 +255,15 @@ func GetAllAsMap(d []byte) (map[string]string, error) {
 	// Skip the header, which is our data length and version.
 	d = d[headSize:]
 
+	return GetAllFromString(string(d))
+}
+
+// GetAllFromString returns a map containing keys and values from a string s containing
+// metadata.
+func GetAllFromString(s string) (map[string]string, error) {
 	// Each metadata entry (key and value) is seperated by a tab, so split at tabs
 	// to get individual entries.
-	entries := strings.Split(string(d), "\t")
+	entries := strings.Split(s, "\t")
 
 	// Go through entries and add to all map.
 	all := make(map[string]string)