JavaScript-Frontend-Entwicklung zur Implementierung binärer Lese- und Schreiboperationen_Javascript-Fähigkeiten

Eine Einführung in die Implementierung binärer Lese- und Schreibvorgänge in der JavaScript-Frontend-Entwicklung finden Sie in der folgenden ausführlichen Erklärung. Dieser Artikel ist sehr detailliert und hat Referenzwert.

Aus verschiedenen Gründen können Binärdateien nicht wie NodeJS im Browser betrieben werden.

Kürzlich eine Hilfsklasse geschrieben, um das Lesen und Schreiben von Binärdateien auf der Browserseite zu steuern

!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 = {
    /**
     * 初始化字节流,把-128至128的区间改为0-256的区间.便于计算
     * @param {Array} array 字节流数组
     * @return {Array} 转化好的字节流数组
     */
    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('不合法字节流')
        }
      }
      return array;
    },
    /**
     * 把一段字符串按照utf8编码写到缓冲区中
     * @param {String} str 将要写入缓冲区的字符串
     * @param {Boolean} isGetBytes 是否只得到内容字节(不包括最开始的两位占位字节)
     * @returns {Array} 字节流
     */
    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 >= 128 && 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);
      }
    },
    /**
     * 把一串字节流按照utf8编码读取出来
     * @param arr 字节流
     * @returns {String} 读取出来的字符串
     */
    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+&#63;(&#63;=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
    },
    /**
     * 转换成Stream对象
     * @param x
     * @returns {Stream}
     */
    convertStream: function (x) {
      if (x instanceof Stream) {
        return x
      } else {
        return new Stream(x)
      }
    },
    /**
     * 把一段字符串转为mqtt格式
     * @param str
     * @returns {*|Array}
     */
    toMQttString: function (str) {
      return this.writeUTF(str)
    }
  };
  /**
   * 读取指定长度的字节流到指定数组中
   * @param {Stream} m Stream实例
   * @param {number} i 读取的长度
   * @param {Array} a 存入的数组
   * @returns {Array} 存入的数组
   */
  function baseRead(m, i, a) {
    var t = a &#63; a : [];
    for (var start = 0; start < i; start++) {
      t[start] = m.pool[m.position++]
    }
    return t
  }
  /**
   * 判断浏览器是否支持ArrayBuffer
   */
  var supportArrayBuffer = (function () {
    return !!window.ArrayBuffer;
  })();
  /**
   * 字节流处理实体类
   * @param {String|Array} array 初始化字节流,如果是字符串则按照UTF8的格式写入缓冲区
   * @constructor
   */
  function Stream(array) {
    if (!(this instanceof Stream)) {
      return new Stream(array);
    }
    /**
     * 字节流缓冲区
     * @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;
    //当前流执行的起始位置
    this.position = 0;
    //当前流写入的多少字节
    this.writen = 0;
    //返回当前流执行的起始位置是否已经大于整个流的长度
    this.check = function () {
      return self.position >= self.pool.length
    };
  }
  /**
   * 强制转换为Stream对象
   * @param x
   * @returns {*|Stream}
   */
  Stream.parse = function (x) {
    return binaryPot.convertStream(x);
  };
  Stream.prototype = {
    /**
     * 从缓冲区读取4个字节的长度并转换为int值,position往后移4位
     * @returns {Number} 读取到的数字
     * @description 如果position大于等于缓冲区的长度则返回-1
     */
    readInt: function () {
      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);
    },
    /**
     * 从缓冲区读取1个字节,position往后移1位
     * @returns {Number}
     * @description 如果position大于等于缓冲区的长度则返回-1
     */
    readByte: function () {
      if (this.check()) {
        return -1
      }
      var val = this.pool[this.position++];
      if (val > 255) {
        val &= 255;
      }
      return val;
    },
    /**
     * 从缓冲区读取1个字节,或读取指定长度的字节到传入的数组中,position往后移1或bytesArray.length位
     * @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();
      }
    },
    /**
     * 从缓冲区的position位置按UTF8的格式读取字符串,position往后移指定的长度
     * @returns {String} 读取的字符串
     */
    readUTF: function () {
      var big = (this.readByte() << 8) | this.readByte();
      return binaryPot.readUTF(this.pool.slice(this.position, this.position += big));
    },
    /**
     * 把字节流写入缓冲区,writen往后移指定的位
     * @param {Number|Array} _byte 写入缓冲区的字节(流)
     * @returns {Array} 写入的字节流
     */
    write: function (_byte) {
      var b = _byte;
      if (Object.prototype.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
    },
    /**
     * 把参数当成char类型写入缓冲区,writen往后移2位
     * @param {Number} v 写入缓冲区的字节
     */
    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
    },
    /**
     * 把字符串按照UTF8的格式写入缓冲区,writen往后移指定的位
     * @param {String} str 字符串
     * @return {Array} 缓冲区
     */
    writeUTF: function (str) {
      var val = binaryPot.writeUTF(str);
      [].push.apply(this.pool, val);
      this.writen += val.length;
    },
    /**
     * 把缓冲区字节流的格式从0至256的区间改为-128至128的区间
     * @returns {Array} 转换后的字节流
     */
    toComplements: function () {
      var _tPool = this.pool;
      for (var i = 0; i < _tPool.length; i++) {
        if (_tPool[i] > 128) {
          _tPool[i] -= 256
        }
      }
      return _tPool
    },
    /**
     * 获取整个缓冲区的字节
     * @param {Boolean} isCom 是否转换字节流区间
     * @returns {Array} 转换后的缓冲区
     */
    getBytesArray: function (isCom) {
      if (isCom) {
        return this.toComplements()
      }
      return this.pool
    },
    /**
     * 把缓冲区的字节流转换为ArrayBuffer
     * @returns {ArrayBuffer}
     * @throw {Error} 不支持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;
});

Wie benutzt man?

<script src="binary.js"></script>
<script>
   var ts = TinyStream('我叫张亚涛');
   ts.writeUTF('你好');
   console.log('获取缓冲区字节流:',ts.getBytesArray());
   console.log('当前的缓冲区position为:',ts.position,'writen为:',ts.writen);
   console.log('读取第一个utf8字节流:',ts.readUTF());
   console.log('当前的缓冲区position为:',ts.position,'writen为:',ts.writen);
   console.log('读取第二个utf8字节流:',ts.readUTF());
   console.log('当前的缓冲区position为:',ts.position,'writen为:',ts.writen);
</script>

Zukünftig muss ich mir keine Gedanken mehr über die binäre Verarbeitung im Browser-Segment machen! ! ! Ich hoffe, dass die Weitergabe dieses Artikels für alle hilfreich sein wird, um Kenntnisse im Zusammenhang mit JavaScript-Binärdateien zu erlernen.