Add grpc codec

codec/grpc/util.go

@@ -0,0 +1,70 @@
+package grpc
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+)
+
+var (
+	maxMessageSize = 1024 * 1024 * 4
+	maxInt         = int(^uint(0) >> 1)
+)
+
+func decode(r io.Reader) (uint8, []byte, error) {
+	header := make([]byte, 5)
+
+	// read the header
+	if _, err := r.Read(header[:]); err != nil {
+		return uint8(0), nil, err
+	}
+
+	// get encoding format e.g compressed
+	cf := uint8(header[0])
+
+	// get message length
+	length := binary.BigEndian.Uint32(header[1:])
+
+	// no encoding format
+	if length == 0 {
+		return cf, nil, nil
+	}
+
+	//
+	if int64(length) > int64(maxInt) {
+		return cf, nil, fmt.Errorf("grpc: received message larger than max length allowed on current machine (%d vs. %d)", length, maxInt)
+	}
+	if int(length) > maxMessageSize {
+		return cf, nil, fmt.Errorf("grpc: received message larger than max (%d vs. %d)", length, maxMessageSize)
+	}
+
+	msg := make([]byte, int(length))
+
+	if _, err := r.Read(msg); err != nil {
+		if err == io.EOF {
+			err = io.ErrUnexpectedEOF
+		}
+		return cf, nil, err
+	}
+
+	return cf, msg, nil
+}
+
+func encode(cf uint8, buf []byte, w io.Writer) error {
+	header := make([]byte, 5)
+
+	// set compression
+	header[0] = byte(cf)
+
+	// write length as header
+	binary.BigEndian.PutUint32(header[1:], uint32(len(buf)))
+
+	// read the header
+	if _, err := w.Write(header[:]); err != nil {
+		return err
+	}
+
+	// write the buffer
+	_, err := w.Write(buf)
+	return err
+}