Just a quick note here, please correct me if I'm lacking.
In this development, we divide the messages to be sent into text type messages and file type messages, file type messages include pictures, documents, audio, video, etc. All messages will be sent through thenew FileReader()method into aarraybuffertype and send it to the server. In order for the server to differentiate between the message types and do the corresponding processing, we need to add the message type in thisarraybufferarraysThe rules for adding some descriptive information, such as message type identification, recipient, etc., are as follows:
#### text type message
Message type identifier:13, which takes up two bytes;
recipientcodeLength:, which takes up two bytes;
recipientcode: toCodeoccupyBytes;
After defining the rules it's time to assemble the data, first defining a newarraybufferobject whose length is:Message type identification 13 (2 bytes)+(2 bytes)+toCode (bytes)+msgArrayBuffer (bytes)The code is as follows:
let msgArrayBuffer = str2ab(textMsg);
let toCodeArrayBuffer = str2ab(toCode);
let sendArrayBuffer = new ArrayBuffer(4 + + ); let sendUint8 = new Uint8Buffer(4 + + )
let sendUint8 = new Uint8Array(sendArrayBuffer); let headUint16 = new Uint8Array(sendArrayBuffer)
let headUint16 = new Uint16Array(sendArrayBuffer , 0, 2); // use double byte reference, take two bits (equivalent to four bytes)
headUint16[0] = 13;//message type
headUint16[1] = ;//
let msgUint8 = new Uint8Array(msgArrayBuffer);// use single byte reference
for (let i = 0; i < ; i++) {// Loop through the arraybuffer to write the text message to be sent
sendUint8[i + 4 + ] = msgUint8[i];
}
(sendUint8)//send
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The server receives the data and parses it according to a set of rules.First take 1 and 2 bytes to differentiate the message type，Take 3 and 4 bytes to get the length of the toCode.，Then take the toCode string from the 5th byte up to the toCode length，The final message is a text message starting one byte back from the toCode length and ending at the end.
#### filetype message
Message type identifier:31(picture, other types can be customized), occupies two bytes;
recipientcodeLength:, which takes up two bytes;
recipientcode: toCodeoccupyBytes;
File name length:, which takes up two bytes;
File Name:fileName, occupyBytes;
After defining the rules it's time to assemble the data, first defining a newarraybufferobject whose length is:Message type identification 31 (2 bytes)+(2 bytes)+(2 bytes)+fileName (bytes)+msgArrayBuffer (bytes), the code can be referred to the text message.
ArrayBufferYou can refer to MDN for the use of/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer