proto: Added functions to unmarshal a raw message body.

diff --git a/proto/proto.go b/proto/proto.go
index 7f53f3d82c0732e2b9643f1937e15eb01e113c6e..91e21122b82ac5013d7bc90bbbe933d7ade4dbd1 100644 (file)
--- a/proto/proto.go
+++ b/proto/proto.go
@@ -30,6 +30,8 @@ package proto
 
 import (
        "encoding/binary"
+       "encoding/json"
+       "fmt"
        "io"
 )
 
@@ -81,6 +83,18 @@ const (
        ConnectionExpr = Status(100)
 )
 
+// The DataType describes the type of data in a ConnectionData message.
+type DataType int
+
+const (
+       // A HostList can be unmarshaled to []sysdb.Host.
+       HostList DataType = iota
+       // A Host can be unmarshaled to sysdb.Host.
+       Host
+       // A Timeseries can be unmarshaled to sysdb.Timeseries.
+       Timeseries
+)
+
 // A Message represents a raw message of the SysDB front-end protocol.
 type Message struct {
        Type Status
@@ -130,4 +144,36 @@ func Write(w io.Writer, m *Message) error {
        return nil
 }
 
+// DataType determines the type of data in a ConnectionData message.
+func (m Message) DataType() (DataType, error) {
+       if m.Type != ConnectionData {
+               return 0, fmt.Errorf("message is not of type DATA")
+       }
+
+       typ := nbo.Uint32(m.Raw[:4])
+       switch Status(typ) {
+       case ConnectionList, ConnectionLookup:
+               return HostList, nil
+       case ConnectionFetch:
+               return Host, nil
+       case ConnectionTimeseries:
+               return Timeseries, nil
+       }
+       return 0, fmt.Errorf("unknown DATA type %d", typ)
+}
+
+// Unmarshal parses the raw body of m and stores the result in the value
+// pointed to by v which has to match the type of the message and its data.
+func Unmarshal(m *Message, v interface{}) error {
+       if m.Type != ConnectionData {
+               return fmt.Errorf("unmarshaling message of type %d not supported", m.Type)
+       }
+       if len(m.Raw) == 0 { // empty command
+               return nil
+       } else if len(m.Raw) < 4 {
+               return fmt.Errorf("DATA message body too short")
+       }
+       return json.Unmarshal(m.Raw[4:], v)
+}
+
 // vim: set tw=78 sw=4 sw=4 noexpandtab :