Initial working version

wire_proto.go

@@ -0,0 +1,44 @@
+package journal
+
+import (
+	"encoding/binary"
+	"io"
+	"net"
+)
+
+var (
+	wireProtocolAttributeSeparator  = []byte{'='}
+	wireProtocolAttributeTerminator = []byte{'\n'}
+)
+
+// WireWrite is the lowest-level routine. It writes a journal entry using the
+// native wire protocol documented at https://systemd.io/JOURNAL_NATIVE_PROTOCOL/ .
+// Invalid attributes are silently skipped. It appends to buf as needed.
+//
+// As long as w supports the net.buffersWriter interface, the write will be
+// atomic, and this function is safe to use across goroutines. Otherwise,
+// writes may be interleaved.
+func WireWrite(buf *net.Buffers, w io.Writer, attrs []Attr) error {
+	for i := range attrs {
+		key := attrs[i].Key.key
+		if key == "" {
+			// silently discard invalid attributes
+			continue
+		}
+
+		*buf = append(*buf, []byte(key))
+		if attrs[i].UseTextProto() {
+			*buf = append(*buf, wireProtocolAttributeSeparator)
+			*buf = append(*buf, attrs[i].Value)
+		} else {
+			var valueSize [9]byte
+			valueSize[0] = '\n'
+			binary.LittleEndian.PutUint64(valueSize[1:], uint64(len(attrs[i].Value)))
+			*buf = append(*buf, valueSize[:])
+			*buf = append(*buf, attrs[i].Value)
+		}
+		*buf = append(*buf, wireProtocolAttributeTerminator)
+	}
+	_, err := buf.WriteTo(w)
+	return err
+}