JavaScript frontend development-Implementation of binary read/write operations-javascript skills

This article describes how to implement binary read/write operations in JavaScript front-end development. For more information, see Introduction to the implementation of binary read/write operations in javascript front-end development, please refer to the following details. This article is very detailed and has reference value.

For various reasons, the browser cannot operate binary like nodejs.

Recently I wrote a help class for reading and writing binary data in a browser.

! Function (entrance) {"use strict"; if ("object" === typeof exports & "undefined "! = Typeof module) {module. exports = entrance ();} else if ("function" === typeof define & define. amd) {define ([], entrance ();} else {var f; if ("undefined "! = Typeof window) {f = window;} else {throw new Error ('wrong execution environment ');} f. tinyStream = entrance () ;}( function () {var binaryPot = {/*** initialize the byte stream and change the range from-128 to 128 to the range from 0. easy to calculate * @ param {Array} array byte stream Array * @ return {array} converted byte stream Array */init: function (array) {for (var I = 0; I <array. length; I ++) {array [I] * = 1; if (array [I] <0) {array [I] + = 256} if (array [I]> 255) {throw new Error ('invalid byte stream')} return array ;}, /*** write a String to the buffer according to UTF-8 encoding * @ param {String} str: String to be written into the buffer * @ param {Boolean} isGetBytes: whether to get only content bytes (not including the first two placeholder bytes) * @ returns {Array} byte stream */writeUTF: function (str, isGetBytes) {var back = [], byteSize = 0; for (var I = 0; I <str. length; I ++) {var code = str. charCodeAt (I); if (code> = 0 & code <= 127) {byteSize + = 1; back. push (code);} else if (code> = 1 28 & code <= 2047) {byteSize + = 2; back. push (192 | (31 & (code> 6); back. push (128 | (63 & code)} else if (code >=2048 & code <= 65535) {byteSize + = 3; back. push (224 | (15 & (code> 12); back. push (128 | (63 & (code> 6); back. push (128 | (63 & code) }}for (I = 0; I <back. length; I ++) {if (back [I]> 255) {back [I] & = 255} if (isGetBytes) {return back} if (byteSize <= 255) {return [0, byteSize]. concat (back);} else {return [byteSize> 8, byteSize & 255]. concat (back );}}, /*** read a String of byte streams according to utf8 encoding * @ param arr byte stream * @ returns {String} Read String */readUTF: function (arr) {if (Object. prototype. toString. call (arr) = "[object String]") {return arr;} var UTF = "", _ arr = this. init (arr); for (var I = 0; I <_ arr. length; I ++) {var one = _ arr [I]. toString (2), v = One. match (/^ 1 +? (? = 0)/); if (v & one. length = 8) {var bytesLength = v [0]. length, store = _ arr [I]. toString (2 ). slice (7-bytesLength); for (var st = 1; st <bytesLength; st ++) {store ++ = _ arr [st + I]. toString (2 ). slice (2)} UTF + = String. fromCharCode (parseInt (store, 2); I + = bytesLength-1} else {UTF ++ = String. fromCharCode (_ arr [I])} return UTF},/*** convert to Stream object * @ param x * @ returns {Stream} */convertStre Am: function (x) {if (x instanceof Stream) {return x} else {return new Stream (x )}}, /*** convert a string to mqtt format * @ param str * @ returns {* | Array} */toMQttString: function (str) {return this. writeUTF (str )}}; /*** read byte streams of the specified length to the specified Array * @ param {Stream} m Stream instance * @ param {number} I read length * @ param {Array} a saved * @ returns {Array} Array */function baseRead (m, i, a) {var t =? A: []; for (var start = 0; start <I; start ++) {t [start] = m. pool [m. position ++]} return t}/*** determines whether the browser supports ArrayBuffer */var supportArrayBuffer = (function () {return !! Window. arrayBuffer;}) ();/*** byte stream processing entity class * @ param {String | Array} array initializes the byte stream, if it is a string, write the buffer * @ constructor */function Stream (array) {if (! (This instanceof Stream) {return new Stream (array);}/*** byte Stream buffer * @ type {Array} */this. pool = []; if (Object. prototype. toString. call (array) = '[object Array]') {this. pool = binaryPot. init (array);} else if (Object. prototype. toString. call (array) = "[object ArrayBuffer]") {var arr = new Int8Array (array); this. pool = binaryPot. init ([]. slice. call (arr);} else if (typeof array = 'string ') {This. pool = binaryPot. writeUTF (array);} var self = this; // the starting position of the current stream execution this. position = 0; // The number of bytes written to the current stream. this. writen = 0; // return whether the starting position of the current stream execution is greater than the length of the whole stream. check = function () {return self. position> = self. pool. length};}/*** forcibly converted to Stream object * @ param x * @ returns {* | Stream} */Stream. parse = function (x) {return binaryPot. convertStream (x) ;}; Stream. prototype = {/*** read the length of 4 bytes from the buffer and convert it to int value, posit Ion moves back 4 digits * @ returns {Number} to read the Number * @ description. If the position is greater than or equal to the length of the buffer,-1 */readInt: function () is returned () {if (this. check () {return-1} var end = ""; for (var I = 0; I <4; I ++) {end + = this. pool [this. position ++]. toString (16)} return parseInt (end, 16) ;},/*** read 1 byte from the buffer, position move back 1 bit * @ returns {Number} * @ description if position is greater than or equal to the length of the buffer,-1 */readByte: function () {if (this. check () {retu Rn-1} var val = this. pool [this. position ++]; if (val> 255) {val & = 255;} return val ;},/*** reads 1 byte from the buffer, or read the specified length of byte to the input array, move position back 1 or bytesArray. length bit * @ param {Array | undefined} bytesArray * @ returns {Array | Number} */read: function (bytesArray) {if (this. check () {return-1} if (bytesArray) {return baseRead (this, bytesArray. length | 0, bytesArray)} else {return this. readByte ();}}, /*** Read the String from the position of the buffer in UTF8 format, and move the position back to the String read by the specified length * @ returns {String} */readUTF: function () {var big = (this. readByte () <8) | this. readByte (); return binaryPot. readUTF (this. pool. slice (this. position, this. position + = big) ;},/*** writes the byte stream to the buffer zone, the specified bit * @ param {Number | Array} _ byte of the buffer written by writen * @ returns {Array} */write: function (_ byte) {var B = _ byte; if (Object. protot Ype. toString. call (B ). toLowerCase () = "[object array]") {[]. push. apply (this. pool, B); this. writen + = B. length;} else {if (+ B = B) {if (B> 255) {B & = 255;} this. pool. push (B); this. writen ++} return B},/*** treats the parameter as a char-type write buffer, writen moves 2 bits back * @ param {Number} v The Byte written to the buffer */writeChar: function (v) {if (+ v! = V) {throw new Error ("writeChar: arguments type is error")} this. write (v >>8) & 255); this. write (v& 255); this. writen + = 2},/*** write the string to the buffer in UTF8 format, the specified position * @ param {String} str String * @ return {Array} buffer */writeUTF: function (str) {var val = binaryPot. writeUTF (str); []. push. apply (this. pool, val); this. writen + = val. length ;}, /*** change the format of the buffer byte stream from 0 to 256 to the range from-128 to 128 * @ returns {Array} to the converted byte stream */toComplements: function () {var _ tPool = this. pool; for (var I = 0; I <_ tPool. length; I ++) {if (_ tPool [I]> 128) {_ tPool [I]-= 256} return _ tPool }, /*** get the bytes of the entire buffer * @ param {Boolean} whether isCom converts the byte stream range * @ returns {Array} the converted buffer */getBytesArray: function (isCom) {if (isCom) {return this. toComplements ()} return this. pool},/*** switch the byte stream of the buffer to ArrayBuffer * @ returns {ArrayBuffer} * @ throw {Error} does not support ArrayBuffer */toArrayBuffer: function () {if (supportArrayBuffer) {return new ArrayBuffer (this. getBytesArray ();} else {throw new Error ('not support arraybuffer') ;}, clear: function () {this. pool = []; this. writen = this. position = 0 ;}}; return Stream ;});

How to use it?