// encode serializes msg and prepends the message header. If msg is nil, it
// generates the message header of 0 message length.
func encode(c grpc.Codec, msg interface{}, cp grpc.Compressor, cbuf *bytes.Buffer) ([]byte, error) {
var b []byte
var length uint
if msg != nil {
var err error
// TODO(zhaoq): optimize to reduce memory alloc and copying.
b, err = c.Marshal(msg)
if err != nil {
return nil, err
}
if cp != nil {
if err := cp.Do(cbuf, b); err != nil {
return nil, err
}
b = cbuf.Bytes()
}
length = uint(len(b))
}
if length > math.MaxUint32 {
return nil, Errorf(codes.InvalidArgument, "grpc: message too large (%d bytes)", length)
}
const (
payloadLen = 1
sizeLen = 4
)
var buf = make([]byte, payloadLen+sizeLen+len(b))
// Write payload format
if cp == nil {
buf[0] = byte(compressionNone)
} else {
buf[0] = byte(compressionMade)
}
// Write length of b into buf
binary.BigEndian.PutUint32(buf[1:], uint32(length))
// Copy encoded msg to buf
copy(buf[5:], b)
return buf, nil
}