Merged in add-extract-all (pull request #138)

stream/mts/meta: added ExtractAll func

Approved-by: Alan Noble <anoble@gmail.com>
Approved-by: kortschak <dan@kortschak.io>

stream/mts/meta/meta.go

@@ -49,9 +49,9 @@ const (
 )
 
 var (
-	errKeyAbsent     = errors.New("Key does not exist in map")
-	errNoHeader      = errors.New("Metadata string does not contain header")
-	errInvalidHeader = errors.New("Metadata string does not contain valid header")
+	errKeyAbsent            = errors.New("Key does not exist in map")
+	errInvalidMeta          = errors.New("Invalid metadata given")
+	errUnexpectedMetaFormat = errors.New("Unexpected meta format")
 )
 
 // Metadata provides functionality for the storage and encoding of metadata
@@ -164,14 +164,11 @@ func (m *Data) Encode() []byte {
 	return m.enc
 }
 
-// ReadFrom extracts a value from a metadata string d, for the given key. If the
-// key is not present in the metadata string, an error is returned. If the
-// metadata header is not present in the string, an error is returned.
-func Extract(key string, d []byte) (string, error) {
-	if d[0] != 0 {
-		return "", errNoHeader
-	} else if d[0] == 0 && binary.BigEndian.Uint16(d[2:headSize]) != uint16(len(d[headSize:])) {
-		return "", errInvalidHeader
+// Get returns the value for the given key in d.
+func Get(key string, d []byte) (string, error) {
+	err := checkMeta(d)
+	if err != nil {
+		return "", err
 	}
 	d = d[headSize:]
 	entries := strings.Split(string(d), "\t")
@@ -183,3 +180,30 @@ func Extract(key string, d []byte) (string, error) {
 	}
 	return "", errKeyAbsent
 }
+
+// GetAll returns metadata keys and values from d.
+func GetAll(d []byte) ([][2]string, error) {
+	err := checkMeta(d)
+	if err != nil {
+		return nil, err
+	}
+	d = d[headSize:]
+	entries := strings.Split(string(d), "\t")
+	all := make([][2]string, len(entries))
+	for i, entry := range entries {
+		kv := strings.Split(entry, "=")
+		if len(kv) != 2 {
+			return nil, errUnexpectedMetaFormat
+		}
+		copy(all[i][:], kv)
+	}
+	return all, nil
+}
+
+// checkHeader checks that a valid metadata header exists in the given data.
+func checkMeta(d []byte) error {
+	if len(d) == 0 || d[0] != 0 || binary.BigEndian.Uint16(d[2:headSize]) != uint16(len(d[headSize:])) {
+		return errInvalidMeta
+	}
+	return nil
+}

stream/mts/meta/meta_test.go

@@ -136,9 +136,9 @@ func TestEncode(t *testing.T) {
 	}
 }
 
-// TestReadFrom checks that we can correctly obtain a value for a partiular key
+// TestGetFrom checks that we can correctly obtain a value for a partiular key
 // from a string of metadata using the ReadFrom func.
-func TestReadFrom(t *testing.T) {
+func TestGetFrom(t *testing.T) {
 	tstMeta := append([]byte{0x00, 0x10, 0x00, 0x12}, "loc=a,b,c\tts=12345"...)
 
 	tests := []struct {
@@ -156,7 +156,7 @@ func TestReadFrom(t *testing.T) {
 	}
 
 	for _, test := range tests {
-		got, err := Extract(test.key, []byte(tstMeta))
+		got, err := Get(test.key, []byte(tstMeta))
 		if err != nil {
 			t.Errorf("Unexpected err: %v\n", err)
 		}
@@ -165,3 +165,26 @@ func TestReadFrom(t *testing.T) {
 		}
 	}
 }
+
+// TestGetAll checks that meta.GetAll can correctly get all metadata
+// from descriptor data.
+func TestGetAll(t *testing.T) {
+	tstMeta := append([]byte{0x00, 0x10, 0x00, 0x12}, "loc=a,b,c\tts=12345"...)
+	want := [][2]string{
+		{
+			"loc",
+			"a,b,c",
+		},
+		{
+			"ts",
+			"12345",
+		},
+	}
+	got, err := GetAll(tstMeta)
+	if err != nil {
+		t.Errorf("Unexpected error: %v\n", err)
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Did not get expected out. \nGot : %v, \nWant: %v\n", got, want)
+	}
+}