前端javascript实现二进制读写操作
由于种种原因，在浏览器中无法像nodejs那样操作二进制。
最近写了一个在浏览器端操作读写二进制的帮助类
!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] &= 0xff;
}
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)
* @see https://zh.wikipedia.org/wiki/UTF-8
* @return {Array} 字节流
*/
writeUTF: function (str, isGetBytes) {
var back = [];
var byteSize = 0;
for (var i = 0; i < str.length; i++) {
var code = str.charCodeAt(i);
if (0x00 <= code && code <= 0x7f) {
byteSize += 1;
back.push(code);
} else if (0x80 <= code && code <= 0x7ff) {
byteSize += 2;
back.push((192 | (31 & (code >> 6))));
back.push((128 | (63 & code)))
} else if ((0x800 <= code && code <= 0xd7ff) || (0xe000 <= code && code <= 0xffff)) {
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++) {
back[i] &= 0xff;
}
if (isGetBytes) {
return back
}
if (byteSize <= 0xff) {
return [0, byteSize].concat(back);
} else {
return [byteSize >> 8, byteSize & 0xff].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 (typeof arr === '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
},
/**
* 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 ? 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 = this.pool.length | 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;
});
如何使用？
<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>
以后，我可以不用为浏览器段处理二进制而发愁了！！！
