Uint8Array to string in Javascript

写作

Little strings

少量数据使用超出异常

1
2
3
4
5
6
7
8
9
/**
 * little arrays (>=100k characters), otherwise
  you'll get exceptions as RangeError : Maximum call 
 * stack size exceeded or Out of stack space.
 * @returns {string}
 */
function uint8arrayToStringMethod(myUint8Arr){
   return String.fromCharCode.apply(null, myUint8Arr);
}

Browser implementation

浏览器环境使用TextEncoder 和 TextDecoder 原生方法实现，注意兼容性。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
/**
 * Convert an Uint8Array into a string.
 *
 * @returns {String}
 */
function Decodeuint8arr(uint8array){
    return new TextDecoder("utf-8").decode(uint8array);
}

/**
 * Convert a string into a Uint8Array.
 *
 * @returns {Uint8Array}
 */
function Encodeuint8arr(myString){
    return new TextEncoder("utf-8").encode(myString);
}

Crossplatform method

跨平台依赖性低运行良好

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
// http://www.onicos.com/staff/iz/amuse/javascript/expert/utf.txt

/* utf.js - UTF-8 <=> UTF-16 convertion
 *
 * Copyright (C) 1999 Masanao Izumo <iz@onicos.co.jp>
 * Version: 1.0
 * LastModified: Dec 25 1999
 * This library is free.  You can redistribute it and/or modify it.
 */

function Utf8ArrayToStr(array) {
    var out, i, len, c;
    var char2, char3;

    out = "";
    len = array.length;
    i = 0;
    while(i < len) {
    c = array[i++];
    switch(c >> 4)
    { 
      case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
        // 0xxxxxxx
        out += String.fromCharCode(c);
        break;
      case 12: case 13:
        // 110x xxxx   10xx xxxx
        char2 = array[i++];
        out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
        break;
      case 14:
        // 1110 xxxx  10xx xxxx  10xx xxxx
        char2 = array[i++];
        char3 = array[i++];
        out += String.fromCharCode(((c & 0x0F) << 12) |
                       ((char2 & 0x3F) << 6) |
                       ((char3 & 0x3F) << 0));
        break;
    }
    }

    return out;
}

Large blocks

大量数据异步情况

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
/**
 * Converts an array buffer to a string
 *
 * @param {Uin8} uint8arr | The buffer to convert
 * @param {Function} callback | The function to call when conversion is complete
 */
function largeuint8ArrToString(uint8arr, callback) {
    var bb = new Blob([uint8arr]);
    var f = new FileReader();
    f.onload = function(e) {
        callback(e.target.result);
    };
    
    f.readAsText(bb);
}

// Usage example
// "Hello" in Uint8Array format
var myuint8Arr = new Uint8Array([72, 101, 108, 108, 111, 32, 33]);

largeuint8ArrToString(myuint8Arr,function(text){
    // Hello
    console.log(text);
});