aeron-client/src/main/java/io/aeron/protocol/DataHeaderFlyweight.java
public static UnsafeBuffer createDefaultHeader(final int sessionId, final int streamId, final int termId)
    {
        final UnsafeBuffer buffer = new UnsafeBuffer(
            BufferUtil.allocateDirectAligned(HEADER_LENGTH, CACHE_LINE_LENGTH));

        buffer.putByte(VERSION_FIELD_OFFSET, CURRENT_VERSION);
        buffer.putByte(FLAGS_FIELD_OFFSET, (byte)BEGIN_AND_END_FLAGS);
        buffer.putShort(TYPE_FIELD_OFFSET, (short)HDR_TYPE_DATA, LITTLE_ENDIAN);
        buffer.putInt(SESSION_ID_FIELD_OFFSET, sessionId, LITTLE_ENDIAN);
        buffer.putInt(STREAM_ID_FIELD_OFFSET, streamId, LITTLE_ENDIAN);
        buffer.putInt(TERM_ID_FIELD_OFFSET, termId, LITTLE_ENDIAN);
        buffer.putLong(RESERVED_VALUE_OFFSET, DEFAULT_RESERVE_VALUE);

        return buffer;
    }
public static UnsafeBuffer createDefaultHeader(final int sessionId, final int streamId, final int termId)
    {
        final UnsafeBuffer buffer = new UnsafeBuffer(
            BufferUtil.allocateDirectAligned(HEADER_LENGTH, CACHE_LINE_LENGTH));

        buffer.putByte(VERSION_FIELD_OFFSET, CURRENT_VERSION);
        buffer.putByte(FLAGS_FIELD_OFFSET, (byte)BEGIN_AND_END_FLAGS);
        buffer.putShort(TYPE_FIELD_OFFSET, (short)HDR_TYPE_DATA, LITTLE_ENDIAN);
        buffer.putInt(SESSION_ID_FIELD_OFFSET, sessionId, LITTLE_ENDIAN);
        buffer.putInt(STREAM_ID_FIELD_OFFSET, streamId, LITTLE_ENDIAN);
        buffer.putInt(TERM_ID_FIELD_OFFSET, termId, LITTLE_ENDIAN);
        buffer.putLong(RESERVED_VALUE_OFFSET, DEFAULT_RESERVE_VALUE);

        return buffer;
    }
Return an initialised default Data Frame Header.

@param sessionId for the header
@param streamId  for the header
@param termId    for the header
@return byte array containing the header