fix attachment lose #900

[procothesky]

Fix the problem that when broadcasting a byte array data to multiple clients in the same room, the client receives 450, 452 and other wrong binaryEvent number messages and has 45x probe header messages missing attachments

[mrniko]

Thank you for the suggested changes.

Is the problem in empty byte arrays handling? I see your code does the same except empty byte arrays filtering

[procothesky]

Thank you for the suggested changes.

Is the problem in empty byte arrays handling? I see your code does the same except empty byte arrays filtering

Thanks for asking, I found two problems when I send byte[] message.

1. When sending a byte[] message to a room, since multiple clients concurrently call the same Packet.initAttachments(jsonSupport.getArrays().size()) method in PacketEncoder.encodePacket(), this will Leading to concurrent modification, the number of attachments is lost or increased when sending messages, causing the client to receive 45x-["event-name",{"placeholder":"true", "num":0}], and no bytes Data attachment. Under the premise that each client does not need new Packet() for the same byte[] message, we can initAttachments() in advance when creating a Packet to avoid concurrent modification and maximize performance.
2. In line 262 of EncoderHandler: outBuf.writeBytes(buf) - buf is an attachment of Packet, which calls AbstractByteBuf#writeBytes(io.netty.buffer.ByteBuf). This method will move buf.readerIndex to the position of buf.readableBytes on the first call to writeBytes(). After that, other clients who read the attachment of this Packet will not be able to read any valid data, which will cause only the header 04 in the byte[] attachment received by the subsequent client.
   Not sure if I made it clear, if I didn't, please let me know

[procothesky]

@mrniko Please review it when you are free #900

[mrniko]

spring package can't be used

[mrniko]

this is what outBuf.writeBytes(buf) exactly does

[mrniko]

there are no empty byte arrays

[mrniko]

the same is done in encodePacket() method