JavaScript前端開發實現二進位讀寫操作_javascript技巧

!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;
});

<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>