in runner-core/src/main/java/org/apache/apisix/plugin/runner/handler/PayloadEncoder.java [45:57]
private ByteBuffer setBody(ByteBuffer payload, byte type) {
byte[] data = new byte[payload.remaining()];
payload.get(data);
ByteBuffer buffer = ByteBuffer.allocate(data.length + 4);
buffer.put(type);
// data length
byte[] length = int2Bytes(data.length, 3);
buffer.put(length);
// data
buffer.put(data);
buffer.flip();
return buffer;
}