How to directly manipulate binary data in js

This time I will show you how js can directly operate binary data. What are the precautions for js to directly operate binary data. The following is a practical case, let's take a look.

First create a new socket:

var socket=new WebSocket("ws://192.168.0.147");

Then define the function to be executed after opening the socket and connecting:

websocket has A property binaryType, which can be set to "blob" or "arraybuffer". The default format is "blob". I forgot to set it to "arraybuffer" when I was working on the project. As a result, when receiving data below, I need to use the Blob object to receive it. .

socket.onopen=function(){
 //发送登录帧，4-20位为手机号
 var loginArr=[0X02,0X02,0X00,0X1E,0X20,0X20,0X20,0X20,0X20,0X20,0X20,0X20,0X20,0X20,0X20,0X20,0X20,0X20,0X20,0X20,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X00,0X0D,0X0A]        
}

The following is converted to bype and sent out:

var loginBuffer=new ArrayBuffer(30);
var loginDataview=new DataView(loginBuffer);
//localstorageuserinfo为缓存在本地的用户手机号
var telArr=localstorageuserinfo.TelPhone; 
var loginTime=tempTrans();
for(var i=0;i<loginArr.length;){
 loginDataview.setInt8(i,loginArr[i]);
 if(i>3&&i<(telArr.length+4)){
   loginDataview.setInt8(i,telArr.charCodeAt(i-4));
 }   
 if(i>19&&i<loginArr.length-2){
  loginDataview.setInt8(i,loginTime[i-20]);
 }
 i++;
}
//登录包
socket.send(loginDataview.buffer);   
//格式化时间同时按照年俩位月日时分秒1位由高到底排序
function tempTrans(time){
 if(!time){
  time=new Date();
 }
 var u32Dataview=new DataView(new Uint16Array([time.getFullYear()]).buffer);
 var uint8=[];
 uint8.push(new DataView(new Uint8Array([0X00]).buffer).getUint8(0))
 for(var i=u32Dataview.byteLength-1;i>=0;i--){
  uint8.push(u32Dataview.getUint8(i))
 }
 uint8.push(new DataView(new Uint8Array([time.getMonth()+1]).buffer).getUint8(0));
 uint8.push(new DataView(new Uint8Array([time.getDate()]).buffer).getUint8(0));
 uint8.push(new DataView(new Uint8Array([time.getHours()]).buffer).getUint8(0));
 uint8.push(new DataView(new Uint8Array([time.getMinutes()]).buffer).getUint8(0));
 uint8.push(new DataView(new Uint8Array([time.getSeconds()]).buffer).getUint8(0));
 return uint8;
}

The sending process is roughly like this. First, create a new ArrayBuffer object, which needs to fill in the buffer length parameter. See the api in detail==> https://msdn.microsoft.com/zh-cn/library/br212474(v=vs.94).aspx,

Then create a new DataView object , pass the ArrayBuffer in. Then use DataView's setUint and getUint methods to read and set bits. For details, refer to api==> https://msdn.microsoft.com/zh-cn/library/br212463(v=vs.94).aspx

The following is the processing of receiving data:

//接收消息onmessage
socket.onmessage=function(data){
  var blob_=new Blob([data.data]);
  parseBlob(blob_);
 }
//使用fileReader操作blob对象
var reader = { 
 readAs: function(type,blob,cb){
  var r = new FileReader();
  r.onloadend = function(){
    if(typeof(cb) === 'function') {
    cb.call(r,r.result);
    }
  }
  try{
    r['readAs'+type](blob);
  }catch(e){}
  }
}
function parseBlob(blob){
 reader.readAs('ArrayBuffer',blob.slice(0,blob.size),function(arr){
 　　var dataview_=new DataView(arr);
 　　//协议中第二位是判断数据来源的
 　　var socketConType=dataview_.getUint8(1);
 　　//转成字符串读取数据
 　　var modulelength=(dataview_.buffer.byteLength-46)/33;
 　　var modulestate={};
 　　　reader.readAs('Text',blob.slice(i*33+37,i*33+37+32),function(result){
  　　modulestate[dataview_.getUint8(i*33+36)]=result;
 　　});
 })
}

After converting it into a string, you can do whatever you want.

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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